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Special Issue: Closing Crop Yield and Efficiency Gaps for Food Security and Sustainable Agriculture
Section 1: Using modeling method to evaluate yield and efficiency gaps
Section 2: The main factors determining yield and efficiency gaps at different levels
Section 3: Physiological mechanisms for closing yield and efficiency gaps
Section 4: Effective management strategies for closing yield and efficiency gaps


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The goal of this special issue of the Journal of Integrative Agriculture is to provide quantitative analyses for yield and efficiency gaps of major crops in main production regions in China. By using the modeling method and field experiments, researchers find determining factors and underlying mechanisms, and provide effective management strategies for closing these gaps. We hope these studies could provide a theoretical basis and technical support for coordinating the high yield and high resource use efficiency in crops in China and even all over the world. The cover image is a combination of crops and fields with different yield and efficiency levels. The photos were provided by the National Key Research and Development Program of China (2016YFD0300100).


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Special Issue: Closing Crop Yield and Efficiency Gaps for Food Security and Sustainable Agriculture

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Editorial — Closing crop yield and efficiency gaps for food security and sustainable agriculture ZHOU Wen-bin, DUAN Feng-ying 2021, 20(2): 343-348.  DOI: 10.1016/S2095-3119(20)63580-8 Abstract ( )   PDF in ScienceDirect

Section 1: Using modeling method to evaluate yield and efficiency gaps

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Yield gap and resource utilization efficiency of three major food crops in the world - A review RONG Liang-bing, GONG Kai-yuan, DUAN Feng-ying, LI Shao-kun, ZHAO Ming, HE Jianqiang, ZHOU Wen-bin, YU Qiang 2021, 20(2): 349-362.  DOI: 10.1016/S2095-3119(20)63555-9 Abstract ( )   PDF in ScienceDirect   Yield gap analysis could provide management suggestions to increase crop yields, while the understandings of resource utilization efficiency could help judge the rationality of the management. Based on more than 110 published papers and data from Food and Agriculture Organization (FAO, www.fao.org/faostat) and the Global Yield Gap and Water Productivity Atlas (www.yieldgap.org), this study summarized the concept, quantitative method of yield gap, yield-limiting factors, and resource utilization efficiency of the three major food crops (wheat, maize and rice). Currently, global potential yields of wheat, maize and rice were 7.7, 10.4 and 8.5 t ha–1, respectively. However, actual yields of wheat, maize and rice were just 4.1, 5.5 and 4.0 t ha–1, respectively. Climate, nutrients, moisture, crop varieties, planting dates, and socioeconomic conditions are the most mentioned yield-limiting factors. In terms of resource utilization, nitrogen utilization, water utilization, and radiation utilization efficiencies are still not optimal, and this review has summarized the main improvement measures. The current research focuses on quantitative potential yield and yield gap, with a rough explanation of yield-limiting factors. Subsequent research should use remote sensing data to improve the accuracy of the regional scale and use machine learning to quantify the role of yield-limiting factors in yield gaps and the impact of change crop management on resource utilization efficiency, so as to propose reasonable and effective measures to close yield gaps.

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Reducing maize yield gap by matching plant density and solar radiation LIU Guang-zhou, LIU Wan-mao, HOU Peng, MING Bo, YANG Yun-shan, GUO Xiao-xia, XIE Rui-zhi, WANG Ke-ru, LI Shao-kun 2021, 20(2): 363-370.  DOI: 10.1016/S2095-3119(20)63363-9 Abstract ( )   PDF in ScienceDirect   Yield gap exists because the current attained actual grain yield cannot yet achieve the estimated yield potential. Chinese high yield maize belt has a wide span from east to west which results in different solar radiations between different regions and thus different grain yields. We used multi-site experimental data, surveyed farmer yield data, the highest recorded yield data in the literatures, and simulations with Hybrid-Maize Model to assess the yield gap and tried to reduce the yield gap by matching the solar radiation and plant density. The maize belt was divided into five regions from east to west according to distribution of accumulated solar radiation. The results showed that there were more than 5.8 Mg ha–1 yield gaps between surveyed farmer yield and the yield potential in different regions of China from east to west, which just achieved less than 65% of the yield potential. By analyzing the multi-site density experimental data, we found that the accumulated solar radiation was significantly correlated to optimum plant density which is the density with the highest yield in the multi-site density experiment (y=0.09895x–32.49, P<0.01), according to which the optimum plant densities in different regions from east to west were calculated. It showed that the optimum plant density could be increased by 60.0, 55.2, 47.3, 84.8, and 59.6% compared to the actual density, the grain yield could be increased by 20.2, 18.3, 10.9, 18.1, and 15.3% through increasing plant density, which could reduce the yield gaps of 33.7, 23.0, 13.4, 17.3, and 10.4% in R (region)-1, R-2, R-3, R-4, and R-5, respectively. This study indicates that matching maize plant density and solar radiation is an effective approach to reduce yield gaps in different regions of China.

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Cultivar selection can increase yield potential and resource use efficiency of spring maize to adapt to climate change in Northeast China SU Zheng-e, LIU Zhi-juan, BAI Fan, ZHANG Zhen-tao, SUN Shuang, HUANG Qiu-wan, LIU Tao, LIU Xiao-qing, YANG Xiao-guang 2021, 20(2): 371-382.  DOI: 10.1016/S2095-3119(20)63359-7 Abstract ( )   PDF in ScienceDirect   Northeast China (NEC) is one of the major maize production areas in China. Agro-climatic resources have obviously changed, which will seriously affect crop growth and development in this region. It is important to investigate the contribution of climate change adaptation measures to the yield and resource use efficiency to improve our understanding of how we can effectively ensure high yield and high efficiency in the future. In this study, we divided the study area into five accumulated temperature zones (ATZs) based on growing degree days (GDD). Based on the meteorological data, maize data (from agro-meteorological stations) and the validated APSIM-Maize Model, we first investigated the spatial distributions and temporal trends of maize potential yield of actual planted cultivars, and revealed the radiation use efficiency (RUE) and heat resource use efficiency (HUE) from 1981 to 2017. Then according to the potential growing seasons and actual growing seasons, we identified the utilization percentages of radiation (PR) resource and heat resource (PH) for each ATZ under potential production from 1981 to 2017. Finally, we quantified the contributions of cultivar changings to yield, PR and PH of maize. The results showed that during the past 37 years, the estimated mean potential yield of actual planted cultivars was 13 649 kg ha–1, ranged from 11 205 to 15 257 kg ha–1, and increased by 140 kg ha–1 per decade. For potential production, the mean values of RUE and HUE for the actual planted maize cultivars were 1.22 g MJ–1 and 8.58 kg (°C d)–1 ha–1. RUE showed an increasing tendency, while HUE showed a decreasing tendency. The lengths of the potential growing season and actual growing season were 158 and 123 d, and increased by 2 and 1 d per decade. PR and PH under potential production were 82 and 86%, respectively and showed a decreasing tendency during the past 37 years. This indicates that actual planted cultivars failed to make full use of climate resources. However, results from the adaptation assessments indicate that, adoption of cultivars with growing season increased by 2–11 d among ATZs caused increase in yield, PR and PH of 0.6–1.7%, 1.1–7.6% and 1.5–8.9%, respectively. Therefore, introduction of cultivars with longer growing season can effectively increase the radiation and heat utilization percentages and potential yield.

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Effects of different agricultural treatments on narrowing winter wheat yield gap and nitrogen use efficiency in China YAO Feng-mei, LI Qin-ying, ZENG Rui-yun, SHI Si-qi 2021, 20(2): 383-394.  DOI: 10.1016/S2095-3119(20)63317-2 Abstract ( )   PDF in ScienceDirect   Under the limited cultivated land area and the pursuit of sustainable agricultural development, it is essential for the safety of grain production to study agricultural management approaches on narrowing the winter wheat yield gap and improving nitrogen use efficiency (NUE) in China. In this study, DSSAT-CERES-Wheat Model is used to simulate winter wheat yield under different agricultural treatments, and we analyze yield gaps and NUE with different management scenarios at regional scales and evaluate the suitable approaches for reducing yield gap and increasing NUE. The results show that, the potential of narrowing yield gap ranges 300–900 kg ha–1 with soil nutrients increase, 400–1 200 kg ha–1 with sowing date adjustment and 0–400 kg ha–1 with planting density increase as well as 700–2 200 kg ha–1 with adding nitrogen fertilizer. Contribution rates of management measures of soil nutrients, sowing date adjusting, planting density, and nitrogen fertilizers are 5–15%, 5–15%, 0–4%, and 10–20%, respectively. Difference in nitrogen partial productivity ranges 3–10 kg kg–1 for soil nutrients, 1–10 kg kg–1 for sowing date adjusting, 1–5 kg kg–1 for planting density increase, and –12–0 kg kg–1 for adding nitrogen fertilizers, respectively. It indicates that four treatments can narrow yield gap and improve the NUE in varying degrees, but increasing nitrogen fertilizer leads to the decrease of NUE.

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Determination of soybean yield gap and potential production in Iran using modeling approach and GIS Alireza NEHBANDANI, Afshin SOLTANI, Ali RAHEMI-KARIZAKI, Amir DADRASI, Faranak NOURBAKHSH 2021, 20(2): 395-407.  DOI: 10.1016/S2095-3119(20)63180-X Abstract ( )   PDF in ScienceDirect   Increasing crop production is necessary to maintain food security for the growing global population. Reducing the gap between actual and potential yield is one of the important ways to increase yield per unit area. Potential yield and the yield gap of soybean were determined for Golestan Province, Iran, using Soybean Simulation Model (SSM-iCrop2) and Geographical Information System (GIS). Information from 24 weather stations and soil data of the region were used. Yield gap and production gap were calculated at county and province levels. The average actual yield of soybean in this province was 2.28 t ha–1 while the province’s potential yield was 4.73 t ha–1, so the yield gap was estimated 2.44 t ha–1. Thus, there is a great potential for increasing soybean yield in Golestan, which is possible through improving crop management of soybean in farmers’ fields. The average water productivity of soybean was estimated to be 0.81 kg m–3. Spatial distribution of water productivity in soybean farms showed that the highest and the lowest water productivities (0.99 and 0.44 kg m–3) were in western and eastern regions of the province, respectively, in accordance to vapour pressure deficit. It was concluded that soybean production in the province could increase by 66% (from 109 970 to 182 170 tons) if 80% of the current yield gap could be removed.

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Developing a process-based and remote sensing driven crop yield model for maize (PRYM–Maize) and its validation over the Northeast China Plain ZHANG Sha, Bai Yun, Zhang Jia-hua, Shahzad ALI 2021, 20(2): 408-423.  DOI: 10.1016/S2095-3119(20)63293-2 Abstract ( )   PDF in ScienceDirect   Spatial dynamics of crop yield provide useful information for improving the production. High sensitivity of crop growth models to uncertainties in input factors and parameters and relatively coarse parameterizations in conventional remote sensing (RS) approaches limited their applications over broad regions. In this study, a process-based and remote sensing driven crop yield model for maize (PRYM–Maize) was developed to estimate regional maize yield, and it was implemented using eight data-model coupling strategies (DMCSs) over the Northeast China Plain (NECP). Simulations under eight DMCSs were validated against the prefecture-level statistics (2010–2012) reported by National Bureau of Statistics of China, and inter-compared. The 3-year averaged result could give more robust estimate than the yearly simulation for maize yield over space. A 3-year averaged validation showed that prefecture-level estimates by PRYM–Maize under DMCS8, which coupled with the development stage (DVS)-based grain-filling algorithm and RS phenology information and leaf area index (LAI), had higher correlation (R, 0.61) and smaller root mean standard error (RMSE, 1.33 t ha–1) with the statistics than did PRYM–Maize under other DMCSs. The result also demonstrated that DVS-based grain-filling algorithm worked better for maize yield than did the harvest index (HI)-based method, and both RS phenology information and LAI worked for improving regional maize yield estimate. These results demonstrate that the developed PRYM–Maize under DMCS8 gives reasonable estimates for maize yield and provides scientific basis facilitating the understanding the spatial variations of maize yield over the NECP.

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Delineating the rice crop activities in Northeast China through regional parametric synthesis using satellite remote sensing time-series data from 2000 to 2015 CAO Dan, FENG Jian-zhong, BAI Lin-yan, XUN Lan, JING Hai-tao, SUN Jin-ke, ZHANG Jia-hua 2021, 20(2): 424-437.  DOI: 10.1016/S2095-3119(20)63458-X Abstract ( )   PDF in ScienceDirect   Accurate rice area extraction and yield simulations are important for understanding how national agricultural policies and environmental issues affect regional spatial changes in rice farming. In this study, an improved regional parametric syntheses approach, that is, the rice zoning adaptability criteria and dynamic harvest index (RZAC-DHI), was established, which can effectively simulate the rice cultivation area and yield at the municipal level. The RZAC was used to extract the rice area using Moderate Resolution Imaging Spectroradiometer time-series data and phenological information. The DHI was calculated independently, and then yield was obtained based on the DHI and net primary productivity (NPP). Based on the above results, we analyzed the spatial–temporal patterns of the rice cultivation area and yield in Northeast China (NEC) during 2000–2015. The results revealed that the methods established in this study can effectively support the yearly mapping of the rice area and yield in NEC, the average precisions of which exceed 90 and 80%, respectively. The rice planting areas are mainly located on the Sanjiang, Songnen and Liaohe plains, China, which are distributed along the Songhua and Liaohe rivers. The rice cultivation area and yield in this region increased significantly from 2000 to 2015, with increases of nearly 58 and 90%, respectively. The rice crop area and yield increased the fastest in Heilongjiang Province, China, whereas small changes occurred in Jilin and Liaoning provinces, China. Their gravity centers exhibited evident northward and eastward shifts, with offset distances of 107 and 358 km, respectively. Moreover, Heilongjiang Province has gradually become the new main rice production region. The methodologies used in this study provide a valuable reference for other related studies, and the spatial-temporal variation characteristics of the rice activities have raised new attention as to how these shifts affect national food security and resource allocation.

Section 2: The main factors determining yield and efficiency gaps at different levels

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Geographic variation in the yield formation of single-season high-yielding hybrid rice in southern China WANG Dan-ying, LI Xu-yi, YE Chang, XU Chun-mei, CHEN Song, CHU Guang, ZHANG Yun-bo, ZHANG Xiu-fu 2021, 20(2): 438-449.  DOI: 10.1016/S2095-3119(20)63360-3 Abstract ( )   PDF in ScienceDirect   Environmental conditions greatly affect the growth of rice. To investigate the geographic differences in yield formation of single-season high-yielding hybrid rice in southern China, experiments were conducted in 2017 and 2018 in the upper and middle–lower reaches of the Yangtze River with 10–30 main locally planted high-yielding hybrid cultivars used as materials. Compared with rice planted in the middle–lower reaches of the Yangtze River, rice planted in the upper reaches has a longer tillering duration, higher accumulated temperature (≥10°C) during tillering period, but lower accumulated temperature and solar radiation from initial booting to maturity. Yield traits comparison between the upper and the middle–lower reaches of Yangtze River showed that the former had 48.1% more panicles per unit area while the latter had 46.4% more grains per panicle; the rice yield in the former was positively correlated with the seed setting rate and the dry matter accumulation before heading, while the latter was positively correlated with grains per panicle and dry matter accumulation from booting to maturity. Comparison of the same variety Tianyouhuazhan planted in different regions showed there was a significant positive correlation between panicle number and the duration of and accumulated temperature during the tillering period (r=0.982**, r=0.993**, respectively), and between grains per panicle and accumulated solar radiation during booting period (r=0.952*). In the upper reaches of the Yangtze River, more than 90% of cultivars with an yield of greater than 11 t ha–1 had an effective panicle number of 250–340 m–2, and there was a significant negative correlation between seed setting rate and grains per panicle; therefore, the high-yielding rice production in these regions with a long effective tillering period (>40 d) should choose varieties with moderate grains per panicle, adopt crop managements such as good fertilizer and water measures during vegetative growth period to ensure a certain number of effective panicles, and to increase the dry matter accumulation before heading. While in regions with a short effective tillering period (<20 d) but good sunshine conditions during the reproductive growth period, such as the middle–lower reaches of the Yangtze River, high-yielding rice production should choose cultivars with large panicles, adopt good water and fertilizer managements during the reproductive growth period to ensure the formation of large panicles and the increase of dry matter accumulation after heading.

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The priority of management factors for reducing the yield gap of summer maize in the north of Huang-Huai-Hai region, China LIU Yue-e, LI Yu-xin, LÜ Tian-fang, XING Jin-feng, XU Tian-jun, CAI Wan-tao, ZHANG Yong, ZHAO Jiu-ran, WANG Rong-huan 2021, 20(2): 450-459.  DOI: 10.1016/S2095-3119(20)63294-4 Abstract ( )   PDF in ScienceDirect   Understanding yield potential, yield gap and the priority of management factors for reducing the yield gap in current intensive maize production is essential for meeting future food demand with the limited resources. In this study, we conducted field experiments using different planting modes, which were basic productivity (CK), farmer practice (FP), high yield and high efficiency (HH), and super high yield (SH), to estimate the yield gap. Different factorial experiments (fertilizer, planting density, hybrids, and irrigation) were also conducted to evaluate the priority of individual management factors for reducing the yield gap between the different planting modes. We found significant differences between the maize yields of different planting modes. The treatments of CK, FP, HH, and SH achieved 54.26, 58.76, 65.77, and 71.99% of the yield potential, respectively. The yield gaps between three pairs: CK and FP, FP and HH, and HH and SH, were 0.76, 1.23 and 0.85 t ha–1, respectively. By further analyzing the priority of management factors for reducing the yield gap between FP and HH, as well as HH and SH, we found that the priorities of the management factors (contribution rates) were plant density (13.29%)>fertilizer (11.95%)>hybrids (8.19%)>irrigation (4%) for FP to HH, and hybrids (8.94%)>plant density (4.84%)>fertilizer (1.91%) for HH to SH. Therefore, increasing the planting density of FP was the key factor for decreasing the yield gap between FP and HH, while choosing hybrids with density and lodging tolerance was the key factor for decreasing the yield gap between HH and SH.

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A new feasible method for yield gap analysis in regions dominanted by smallholder farmers, with a case study of Jiangsu Province, China SHAO Jing-jing, ZHAO Wen-qing, ZHOU Zhi-guo, DU Kang, KONG Ling-jie, WANG You-hua 2021, 20(2): 460-469.  DOI: 10.1016/S2095-3119(20)63384-6 Abstract ( )   PDF in ScienceDirect   In the regions where crops were mostly produced by smallholder farmers, the analysis of yield gap is difficult due to diverse cultivars, crop managements and yield levels. In order to find an effective method that can reasonably verify the yield gap and the limiting cultivation factors in narrowing yield gaps in areas that are dominanted by smallholder farmers, we worked out a method consisting five progressive procedures as follows: questionnaire investigation of farmer cultivation regime, identification of yield levels and yield gaps, generalization of key cultivation measurements, reconstruction of representative maize populations, and process-based analysis of yield gap. A case study was carried out in Jiangsu Province, China, in which maize is mostly produced by smallholder farmers. A questionnaire investigation of 1 023 smallholder farmers was carried out firstly, then the frequency distribution of maize yield was simulated by an normal distribution function, and then the covering range and average value of the basic yield, farmer yield and high-yield farmer yield levels were calculated out from the equation. Hereby, the yield gaps 1, 2 and 3 were calculated along with the record highest yield from literature and experts, which were 2 564, 2 346 and 2 073 kg ha–1, respectively. Moreover, with the covering range of each yield level, the suveyed farmers belonging to each yield level were grouped together and then their major cultivation measures were traced and generalized. With the generalized cultivation measures, representative maize populations of the four yield levels were reconstructed, and thereby clarifing lots of characters of the populations or single plant of each population with process-based analysis of the reconstructed populations. In this case, the main factors causing the yield gap were plant density, fertilizer application rate, logging caused by hurricane, and damages caused by pests. The case study primarily indicated that this five-step method is feasible and effective in yield gap study, especially in smallholder farmers dominant regions.

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Spatial variation of technical efficiency of cereal production in China at the farm level ZHOU Wen-bin, WANG Huai-yu, HU Xi, DUAN Feng-ying 2021, 20(2): 470-481.  DOI: 10.1016/S2095-3119(20)63579-1 Abstract ( )   PDF in ScienceDirect   Rice, wheat and maize are the main staple food crops to ensure the food security in China with diversified climate condition, cropping system and environmental and socio-economic factors across provinces. Spatial variation of technical efficiency in farmers’ field is helpful to understand the potential to improve farmers’ yield given the inputs level and reduce the yield gap. The study is based on a large-scale farm household survey which covered 1 218 rice farmers, 3 566 wheat farmers and 2 111 maize farmers in the main producing areas. The results indicate that rice farmers are with very high technical efficiency level, nearly 0.9 on average, with little room to improve the efficiency of agricultural inputs. Similar results have been found in wheat and maize farmers’ fields, although the technical efficiency levels are lower than that of rice farmers while still at a high level with obvious variation across regions. Farmers with higher yield level also achieve better technical efficiency in most locations. Both local environmental and socio-economic factors significantly affect farmers’ technical efficiency. In the context of urbanization and economic development, improved and new agricultural technologies need to be prioritized and facilitated to improve cereal yield at farm level.

Section 3: Physiological mechanisms for closing yield and efficiency gaps

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The effect of solar radiation change on the maize yield gap from the perspectives of dry matter accumulation and distribution YANG Yun-shan, GUO Xiao-xia, LIU Hui-fang, LIU Guang-zhou, LIU Wan-mao, MING Bo, XIE Rui-zhi, WANG Ke-ru, HOU Peng, LI Shao-kun 2021, 20(2): 482-493.  DOI: 10.1016/S2095-3119(20)63581-X Abstract ( )   PDF in ScienceDirect   The uneven distribution of solar radiation is one of the main reasons for the variations in the yield gap between different regions in China and other countries of the world. In this study, different solar radiation levels were created by shading and the yield gaps induced by those levels were analyzed by measuring the aboveground and underground growth of maize. The experiments were conducted in Qitai, Xinjiang, China, in 2018 and 2019. The maize cultivars Xianyu 335 (XY335) and Zhengdan 958 (ZD958) were used with planting density of 12×104 plants ha–1 under either high solar radiation (HSR) or low solar radiation (LSR, 70% of HSR). The results showed that variation in the solar radiation resulted in a yield gap and different cultivars behaved differently. The yield gaps of XY335 and ZD958 were 8.9 and 5.8 t ha–1 induced by the decreased total intercepted photosynthetically active radiation (TIPAR) of 323.1 and 403.9 MJ m–2 from emergence to the maturity stage, respectively. The average yield of XY335 was higher than that of ZD958 under HSR, while the average yield of ZD958 was higher than that of XY335 under LSR. The light intercepted by the canopy and the photosynthetic rates both decreased with decreasing solar radiation. The aboveground dry matter decreased by 11.1% at silking and 21% at maturity, and the dry matter of vegetative organs and reproductive organs decreased by 9.8 and 20.9% at silking and by 12.1 and 25.5% at physiological maturity, respectively. Compared to the HSR, the root weights of XY335 and ZD958 decreased by 54.6 and 45.5%, respectively, in the 0–60 cm soil layer under LSR at silking stage. The aboveground and underground growth responses to different solar radiation levels explained the difference in yield gap. Selecting suitable cultivars can increase maize yield and reduce the yield gaps induced by variation of the solar radiation levels in different regions or under climate change.

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Increasing photosynthetic performance and post-silking N uptake by moderate decreasing leaf source of maize under high planting density CAO Yu-jun, WANG Li-chun, GU Wan-rong, WANG Yong-jun, ZHANG Jun-hua 2021, 20(2): 494-510.  DOI: 10.1016/S2095-3119(20)63378-0 Abstract ( )   PDF in ScienceDirect   To date, little attention has been paid to the effects of leaf source reduction on photosynthetic matter production, root function and post-silking N uptake characteristics at different planting densities. In a 2-year field experiment, Xianyu 335, a widely released hybrid in China, was planted at 60 000 plants ha–1 (conventional planting density, CD) and 90 000 plants ha–1 (high planting density, HD), respectively. Until all the filaments protruded from the ear, at which point the plants were subjected to the removal of 1/2 (T1), 1/3 (T2) and 1/4 (T3) each leaf length per plant, no leaf removal served as the control (CK). We evaluated the leaf source reduction on canopy photosynthetic matter production and N accumulation of different planting densities. Under CD, decreasing leaf source markedly decreased photosynthetic rate (Pn), effective quantum yield of photosystem II (ΦPSII) and the maximal efficiency of photosystem II photochemistry (Fv/Fm) at grain filling stage, reduced post-silking dry matter accumulation, harvest index (HI), and the yield. Compared with the CK, the 2-year average yields of T1, T2 and T3 treatments decreased by 35.4, 23.8 and 8.3%, respectively. Meanwhile, decreasing leaf source reduced the root bleeding sap intensity, the content of soluble sugar in the bleeding sap, post-silking N uptake, and N accumulation in grain. The grain N accumulation in T1, T2 and T3 decreased by 26.7, 16.5 and 12.8% compared with CK, respectively. Under HD, compared to other treatments, excising T3 markedly improved the leaf Pn, ΦPSII and Fv/Fm at late-grain filling stage, increased the post-silking dry matter accumulation, HI and the grain yield. The yield of T3 was 9.2, 35.7 and 20.1% higher than that of CK, T1 and T2 on average, respectively. The T3 treatment also increased the root bleeding sap intensity, the content of soluble sugar in the bleeding sap and post-silking N uptake and N accumulation in grain. Compared with CK, T1 and T2 treatments, the grain N accumulation in T3 increased by 13.1, 40.9 and 25.2% on average, respectively. In addition, under the same source reduction treatment, the maize yield of HD was significantly higher than that of CD. Therefore, planting density should be increased in maize production for higher grain yield. Under HD, moderate decreasing leaf source improved photosynthetic performance and increased the post-silking dry matter accumulation and HI, and thus the grain yield. In addition, the improvement of photosynthetic performance improved the root function and promoted post-silking N uptake, which led to the increase of N accumulation in grain.

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Effects of nitrogen fertilizer and chemical regulation on spring maize lodging characteristics, grain filling and yield formation under high planting density in Heilongjiang Province, China LIU Xiao-ming, GU Wan-rong, LI Cong-feng, LI Jing, WEI Shi 2021, 20(2): 511-526.  DOI: 10.1016/S2095-3119(20)63403-7 Abstract ( )   PDF in ScienceDirect   Now, lodging is a major constraint factor contributing to yield loss of maize (Zea mays L.) under high planting density. Chemical regulation and nitrogen fertilizer could effectively coordinate the relationship between stem lodging and maize yield, which significantly reduce lodging and improve the grain yield. The purpose of this study was to explore the effects of chemical regulation and different nitrogen application rates on lodging characteristics, grain filling and yield of maize under high density. For this, we established a field study during 2017 and 2018 growing seasons, with three nitrogen levels of N100 (100 kg ha–1), N200 (200 kg ha–1) and N300 (300 kg ha–1) at high planting density (90 000 plants ha–1), and applied plant growth regulator (Yuhuangjin, the mixture of 3% DTA-6 and 27% ethephon) at the 7th leaf. The results showed that chemical control increased the activities of phenylalanine ammonia-lyase (PAL), tyrosine ammonia-lyase (TAL), 4-coumarate:CoA ligase (4CL), and cinnamyl alcohol dehydrogenase (CAD), and increased the lignin, cellulose and hemicellulose contents at the bottom of the 3rd internode, which significantly reduced the lodging percentage. The lignin-related enzyme activities, lignin, cellulose and hemicellulose contents decreased with the increase of nitrogen fertilizer, which significantly increased the lodging percentage. The 200 kg ha–1 nitrogen application and chemical control increased the number, diameter, angle, volume, and dry weight of brace roots. The 200 kg ha–1 nitrogen application and chemical control significantly increased the activities of ADP-glucose pyrophosphorylase (AGPase), soluble starch synthase (SSS) and starch branching enzyme (SBE), which promoted the starch accumulation in grains. Additional, improved the maximum grain filling rate (Vmax) and mean grain filling rate (Vm), which promoted the grain filling process, significantly increased grain weight and grain number per ear, thus increased the final yield.

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In situ measurements of winter wheat diurnal changes in photosynthesis and environmental factors reveal new insight into photosynthesis improvement by super-high-yield cultivation MA Ming-yang, LIU Yang, ZHANG Yao-wen, QIN Wei-long, WANG Zhi-min, ZHANG Ying-hua, LU Cong-ming, LU Qing-tao 2021, 20(2): 527-539.  DOI: 10.1016/S2095-3119(20)63554-7 Abstract ( )   PDF in ScienceDirect   In past 30 years, the wheat yield per unit area of China has increased by 79%. The super-high-yield (SH) cultivation played an important role in improving the wheat photosynthesis and yield. In order to find the ecophysiological mechanism underneath the high photosynthesis of SH cultivation, in situ diurnal changes in the photosynthetic gas exchange and chlorophyll (Chl) a fluorescence of field-grown wheat plants during the grain-filling stage and environmental factors were investigated. During the late grain-filling stage at 24 days after anthesis (DAA), the diurnal changes in net CO2 assimilation rate were higher under SH treatment than under high-yield (H) treatment. From 8 to 24 DAA, the actual quantum yield of photosystem II (PSII) electron transport in the light-adapted state (ΦPSII) in the flag leaves at noon under SH treatment were significantly higher than those under H treatment. The leaf temperature, soil temperature and soil moisture were better suited for higher rates of leaf photosynthesis under SH treatment than those under H treatment at noon. Such diurnal changes in environmental factors in wheat fields could be one of the mechanisms for the higher biomass and yield under SH cultivation than those under H cultivation. ΦPSII and CO2 exchange rate in wheat flag leaves under SH and H treatments had a linear correlation which could provide new insight to evaluate the wheat photosynthesis performance under different conditions.

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Effects of nitrogen application rate and hill density on rice yield and nitrogen utilization in sodic saline–alkaline paddy fields GUO Xiao-hong*, LAN Yu-chen*, XU Ling-qi, YIN Da-wei, LI Hong-yu, QIAN Yong-de, ZHENG Gui-ping, LÜ Yan-dong 2021, 20(2): 540-553.  DOI: 10.1016/S2095-3119(20)63479-7 Abstract ( )   PDF in ScienceDirect   Soil salinity and alkalinity can inhibit crop growth and reduce yield, and this has become a global environmental concern. Combined changes in nitrogen (N) application and hill density can improve rice yields in sodic saline–alkaline paddy fields and protect the environment. We investigated the interactive effects of N application rate and hill density on rice yield and N accumulation, translocation and utilization in two field experiments during 2018 and 2019 in sodic saline–alkaline paddy fields. Five N application rates (0 (control), 90, 120, 150, and 180 kg N ha−1 (N0–N4), respectively) and three hill densities (achieved by altering the distance between hills, in rows spaced 30 cm apart: 16.5 cm (D1), 13.3 cm (D2) and 10 cm (D3)) were utilized in a split-plot design with three replicates. Nitrogen application rate and hill density significantly affected grain yield. The mathematical model of quadratic saturated D-optimal design showed that with an N application rate in the range of 0–180 kg N ha−1, the highest yield was obtained at 142.61 kg N ha−1 which matched with a planting density of 33.3×104 ha−1. Higher grain yield was mainly attributed to the increase in panicles m–2. Nitrogen application rate and hill density significantly affected N accumulation in the aboveground parts of rice plants and showed a highly significant positive correlation with grain yield at maturity. From full heading to maturity, the average N loss rate of the aboveground parts of rice plants in N4 was 70.21% higher than that of N3. This is one of the reasons why the yield of N4 treatment is lower than that of the N3 treatment. Nitrogen accumulation rates in the aboveground parts under treatment N3 (150 kg N ha−1) were 81.68 and 106.07% higher in 2018 and 2019, respectively, than those in the control. The N translocation and N translocation contribution rates increased with the increase in the N application rate and hill density, whereas N productivity of dry matter and grain first increased and then decreased with the increase in N application rate and hill density. Agronomic N-use efficiency decreased with an increase in N application rate, whereas hill density did not significantly affect it. Nitrogen productivity of dry matter and grain, and agronomic N-use efficiency, were negatively correlated with grain yield. Thus, rice yield in sodic saline–alkaline paddy fields can be improved by combined changes in the N application rate and hill density to promote aboveground N accumulation. Our study provides novel evidence regarding optimal N application rates and hill densities for sodic saline–alkaline rice paddies.

Section 4: Effective management strategies for closing yield and efficiency gaps

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Differences of yield and nitrogen use efficiency under different applications of slow release fertilizer in spring maize LI Guang-hao, CHENG Gui-gen, LU Wei-ping, LU Da-lei 2021, 20(2): 554-564.  DOI: 10.1016/S2095-3119(20)63315-9 Abstract ( )   PDF in ScienceDirect   Excessive or insufficient application of fertilizer has raised broader concerns regarding soil and environmental degradation. One-time application of slow release fertilizer (SF) has been widely used to reduce yield gap with potential maize yield and improve nitrogen use efficiency (NUE). A 2-year field experiment (2018–2019) was conducted to evaluate the effects of SF rates from 0 to 405 kg N ha–1 (named F0, SF225, SF270, SF315, SF360, and SF405) and 405 kg N ha–1 of common fertilizer (CF405) on the grain yield, biomass and N accumulation, enzymatic activities related with carbon–nitrogen metabolism, NUE and economic analysis. Results indicated that the highest grain yields, NUEs and economic returns were achieved at SF360 in both varieties. The enzymatic activities related with carbon–nitrogen metabolism, pre- and post-silking accumulation of biomass and N increased with increasing SF rate, and they were the highest at SF360 and SF405. The grain yield at SF360 had no significant difference with that at SF405. However, the N partial factor productivity, N agronomic efficiency and N recovery efficiency at SF360 were 9.8, 6.6 and 8.9% higher than that at SF405. The results also indicated that the average grain yields, NUE and economic benefit at SF405 were 5.2, 12.3 and 18.1% higher than that at CF405. In conclusion, decreasing N rate from 405 kg ha–1 (CF) to 360 kg ha–1 (SF) could effectively reduce the yield gap between realized and potential maize yields. The N decreased by 11.1%, but the yield, NUE and economic benefit increased by 3.2, 22.2 and 17.5%, which created a simple, efficient and business-friendly system for spring maize production in Jiangsu Province, China.

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Improving grain yield, nitrogen use efficiency and radiation use efficiency by dense planting, with delayed and reduced nitrogen application, in double cropping rice in South China FU You-qiang, ZHONG Xu-hua, ZENG Jia-huan, LIANG Kai-ming, PAN Jun-feng, XIN Ying-feng, LIU Yan-zhuo, HU Xiang-yu, PENG Bi-lin, CHEN Rong-bing, HU Rui, HUANG Nong-rong 2021, 20(2): 565-580.  DOI: 10.1016/S2095-3119(20)63380-9 Abstract ( )   PDF in ScienceDirect   Improving both grain yield and resource use efficiencies simultaneously is a major challenge in rice production. However, few studies have focused on integrating dense planting with delayed and reduced nitrogen application to enhance grain yield, nitrogen use efficiency (NUE) and radiation use efficiency (RUE) in rice (Oryza sativa L.) in the double rice cropping system in South China. A high-yielding indica hybrid rice cultivar (Yliangyou 143) was grown in field experiments in Guangxi, South China, with three cultivation managements: farmers’ practice (FP), dense planting with equal N input and delayed N application (DPEN) and dense planting with reduced N input and delayed N application (DPRN). The grain yields of DPRN reached 10.6 and 9.78 t ha–1 in the early and late cropping seasons, respectively, which were significantly higher than the corresponding yields of FP by 23.9–29.9%. The grain yields in DPEN and DPRN were comparable. NUE in DPRN reached 65.2–72.9 kg kg–1, which was 61.2–74.1% higher than that in FP and 24.6–30.2% higher than that in DPEN. RUE in DPRN achieved 1.60–1.80 g MJ–1, which was 28.6–37.9% higher than that in FP. The productive tiller percentage in DPRN was 7.9–36.2% higher than that in DPEN. Increases in crop growth rate, leaf area duration, N uptake from panicle initiation to heading and enhancement of the apparent transformation ratio of dry weight from stems and leaf sheaths to panicles all contributed to higher grain yield and higher resource use efficiencies in DPRN. Correlation analysis revealed that the agronomic and physiological traits mentioned above were significantly and positively correlated with grain yield. Comparison trials carried out in Guangdong in 2018 and 2019 also showed that DPRN performed better than DPEN. We conclude that DPRN is a feasible approach for simultaneously increasing grain yield, NUE and RUE in the double rice cropping system in South China.

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Effects of mechanized deep placement of nitrogen fertilizer rate and type on rice yield and nitrogen use efficiency in Chuanxi Plain, China ZHU Cong-hua, OUYANG Yu-yuan, DIAO You, YU Jun-qi, LUO Xi, ZHENG Jia-guo, LI Xu-yi 2021, 20(2): 581-592.  DOI: 10.1016/S2095-3119(20)63456-6 Abstract ( )   PDF in ScienceDirect   This paper investigates the yield and nitrogen use efficiency (NUE) of machine-transplanted rice cultivated using mechanized deep placement of N fertilizer in the rice–wheat rotation region of Chuanxi Plain, China. It provides theoretical support for N-saving and improves quality and production efficiency of machine-transplanted rice. Using a single-factor complete randomized block design in field experiments in 2018 and 2019, seven N-fertilization treatments were applied, with the fertilizer being surface broadcast and/or mechanically placed beside the seedlings at (5.5±0.5) cm soil depth when transplanting. The treatments were: N0, no N fertilizer; U1, 180 kg N ha–1 as urea, surface broadcast manually before transplanting; U2, 108 kg N ha–1 as urea, surface broadcast manually before transplanting, and 72 kg N ha–1 as urea surface broadcast manually on the 10th d after transplanting, which is not only the local common fertilization method, but also the reference treatment; UD, 180 kg N ha–1 as urea, mechanically deep-placed when transplanting; M1, 81.6 kg N ha–1 as urea and 38.4 kg N ha–1 as controlled-release urea (CRU), mechanically deep-placed when transplanting; M2, 102 kg N ha–1 as urea and 48 kg N ha–1 as CRU, mechanically deep-placed when transplanting; M3, 122.4 kg N ha–1 as urea and 57.6 kg N ha–1 as CRU, mechanically deep-placed when transplanting. The effects of the N fertilizer treatments on rice yield and NUE were consistent in the 2 yr. With a N application rate of 180 kg ha–1, compared with U2, the N recovery efficiency (NRE), N agronomic use efficiency (NAE) and yield under the UD treatment were 20.6, 3.5 and 1.1% higher in 2018, and 4.6, 1.7 and 1.2% higher in 2019, respectively. Compared with urea alone (U1, U2 or UD), the NRE, NAE and yield achieved by M3 (combined application of urea and controlled-release urea) were higher by 9.2–73.3%, 18.6–61.5% and 6.5–16.5% (2018), and 22.2–65.2%, 25.6–75.0% and 5.9–13.9% (2019), respectively. Compared with M3, the lower-N treatments M1 and M2 significantly increased NRE by 4.0–7.8% in 2018 and 3.1–4.3% in 2019, respectively. Compared with urea surface application (U1 or U2), the yield under the M2 treatment was higher by 4.3–12.9% in 2018 and 3.6–10.1% in 2019, respectively. Compared with U2, the NRE and NAE under the M2 treatment was higher by 36.9 and 36.3% in 2018, and 33.2 and 37.4% in 2019, mainly because of higher N uptake. There was no significant difference in the concentration of nitrate in the top 0–20 cm soil under U1, U2 and M2 treatments during the full heading and maturity stages. During the full heading stage, U2 produced the highest concentration of nitrite in 0–20 cm and 20–40 cm soil among the N fertilizer treatments. In conclusion, mechanized deep placement of mixed urea and controlled-release urea (M2) at transplanting is a highly-efficient cultivation technology that enables increased yield of machine-transplanted rice and improved NUE, while reducing the amount of N-fertilization applied.

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Effects of deep vertical rotary tillage on the grain yield and resource use efficiency of winter wheat in the Huang-Huai-Hai Plain of China WU Fen, ZHAI Li-chao, XU Ping, ZHANG Zheng-bin, Elamin Hafiz BAILLO, Lemessa Negasa TOLOSA, Roy Njoroge KIMOTHO, JIA Xiu-ling, GUO Hai-qian 2021, 20(2): 593-605.  DOI: 10.1016/S2095-3119(20)63405-0 Abstract ( )   PDF in ScienceDirect   Tillage represents an important practice that is used to dynamically regulate soil properties, and affects the grain production process and resource use efficiency of crops. The objectives of this 3-year field study carried out in the Huang-Huai-Hai (HHH) Plain of China were to compare the effects of a new deep vertical rotary tillage (DVRT) with the conventional shallow rotary tillage (CT) on soil properties, winter wheat (Triticum aestivum L.) grain yield and water and nitrogen use efficiency at different productivity levels, and to identify a comprehensive management that optimizes both grain yield and resource use efficiency in the HHH Plain. A split-plot design was adopted in field experiments in the winter wheat growing seasons of 2016–2017 (S1), 2017–2018 (S2) and 2018–2019 (S3), with DVRT (conducted once in June 2016) and CT performed in the main plots. Subplots were treated with one of four targeted productivity level treatments (SH, the super high productivity level; HH, the high productivity and high efficiency productivity level; FP, the farmer productivity level; ISP, the inherent soil productivity level). The results showed that the soil bulk density was reduced and the soil water content at the anthesis stage was increased in all three years, which were due to the significant effects of DVRT. Compared with CT, grain yields, partial factor productivity of nitrogen (PFPN), and water use efficiency (WUE) under DVRT were increased by 22.0, 14.5 and 19.0%. Path analysis and direct correlation decomposition uncovered that grain yield variation of winter wheat was mostly contributed by the spike numbers per area under different tillage modes. General line model analysis revealed that tillage mode played a significant role on grain yield, PFPN and WUE not only as a single factor, but also along with other factors (year and productivity level) in interaction manners. In addition, PFPN and WUE were the highest in HH under DVRT in all three growth seasons. These results provided a theoretical basis and technical support for coordinating the high yield with high resource use efficiency of winter wheat in the resource-restricted region in the HHH Plain of China.

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Improving winter wheat grain yield and water-/nitrogen-use efficiency by optimizing the micro-sprinkling irrigation amount and nitrogen application rate LI Jin-peng, ZHANG Zhen, YAO Chun-sheng, LIU Yang, WANG Zhi-min, FANG Bao-ting, ZHANG Ying-hua 2021, 20(2): 606-621.  DOI: 10.1016/S2095-3119(20)63407-4 Abstract ( )   PDF in ScienceDirect   Available irrigation resources are becoming increasingly scarce in the North China Plain (NCP), and nitrogen-use efficiency of crop production is also relatively low. Thus, it is imperative to improve the water-use efficiency (WUE) and nitrogen fertilizer productivity on the NCP. Here, we conducted a two-year field experiment to explore the effects of different irrigation amounts (S60, 60 mm; S90, 90 mm; S120, 120 mm; S150, 150 mm) and nitrogen application rates (150, 195 and 240 kg ha–1; denoted as N1, N2 and N3, respectively) under micro-sprinkling with water and nitrogen combined on the grain yield (GY), yield components, leaf area index (LAI), flag leaf chlorophyll content, dry matter accumulation (DM), WUE, and nitrogen partial factor productivity (NPFP). The results indicated that the GY and NPFP increased significantly with increasing irrigation amount, but there was no significant difference between S120 and S150; WUE significantly increased first but then decreased with increasing irrigation and S120 achieved the highest WUE. The increase in nitrogen was beneficial to improving the GY and WUE in S60 and S90, while the excessive nitrogen application (N3) significantly reduced the GY and WUE in S120 and S150 compared with those in the N2 treatment. The NPFP significantly decreased with increasing nitrogen rate under the same irrigation treatments. The synchronous increase in spike number (SN) and 1 000-grain weight (TWG) was the main reason for the large increase in GY by micro-sprinkling with increasing irrigation, and the differences in SN and TGW between S120 and S150 were small. Under S60 and S90, the TGW increased with increasing nitrogen application, which enhanced the GY, while N2 achieved the highest TWG in S120 and S150. At the filling stage, the LAI increased with increasing irrigation, and greater amounts of irrigation significantly increased the chlorophyll content in the flag leaf, which was instrumental in increasing DM after anthesis and increasing the TGW. Micro-sprinkling with increased amounts of irrigation or excessive nitrogen application decreased the WUE mainly due to the increase in total water consumption (ET) and the small increase or decrease in GY. Moreover, the increase in irrigation increased the total nitrogen accumulation or contents (TNC) of plants at maturity and reduced the residual nitrate-nitrogen in the soil (SNC), which was conducive to the increase in NPFP, but there was no significant difference in TNC between S120 and S150. Under the same irrigation treatments, an increase in nitrogen application significantly increased the residual SNC and decreased the NPFP. Overall, micro-sprinkling with 120 mm of irrigation and a total nitrogen application of 195 kg ha–1 can lead to increases in GY, WUE and NPFP on the NCP.

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Improving maize grain yield by formulating plant growth regulator strategies in North China GONG Li-sha, QU Shu-jie, HUANG Guan-min, GUO Yu-ling, ZHANG Ming-cai, LI Zhao-hu, ZHOU Yu-yi, DUAN Liu-sheng 2021, 20(2): 622-632.  DOI: 10.1016/S2095-3119(20)63453-0 Abstract ( )   PDF in ScienceDirect   Plant growth regulators (PGRs) are artificially synthesized compounds that have become an important technical guarantee for agricultural production. EDAH (containing 27% ethephon and 3% DA-6) has been proven to inhibit stalk elongation, promote stalk bold and increase mechanical strength and number of vascular bundles. DA-6 could enhance plant photosynthetic capacity and promote cell division and growth. In our study, experiments were performed at summer maize growing season during 2018–2019. The result showed that plant height, ear height and center of gravity height of maize with EDAH+DA-6 treatment were decreased by 10.18, 16.77 and 13.21%, respectively; leaf area and leaf area index also significantly (P<0.001) decreased by 24.11 and 60.15%, respectively; the value of mean tilt angle significantly (P<0.001) increased by 16.72% compared with the control plants, which meant that EDAH+DA-6 could shape more compact plant type. Therefore, lodging rate of maize with EDAH+DA-6 treatment decreased by 6.95% compared with control plants, and the grain yield was increased by 15.51%. In addition, EDAH+DA-6 treatment significantly improved the quality of maize base stalks, such as improving mechanical properties, which increased maize base stalk crushing strength by 22.23%; increased the hemicellulose, cellulose and lignin contents by 6.93, 3.87 and 30.21%, respectively. In conclusion, EDAH+DA-6 treatment could improve summer maize yield by shaping plant morphological characteristics and group photosynthesis.