【Objective】 The effects of different fertilization depths of controlled-release urea on nitrogen absorption and utilization were investigated, and then the suitable fertilization depth for achieving high, efficient and stable yield of controlled- release urea in the Huang-Huai-Hai summer maize area was determined.【Method】 Zhengdan958 was selected as the test variety under field conditions, and seven treatments were set, including no nitrogen fertilizer (CK), surface application (DP0), furrow dressing depth of 5 cm (DP5), 10 cm (DP10), 15 cm (DP15), 20 cm (DP20) and 25 cm (DP25). The effects of urea application depth on growth, yield and nitrogen utilization of summer maize were studied systematically.【Result】Under the same amount of controlled-release urea application, the yield of summer maize was significantly affected by fertilization depth. The yield of summer maize increased at first and then decreased with the increase of basal fertilization depth. Moreover, the relationship between maize yield and fertilization depth in the summer of 2013 and 2014 conformed to the quadratic curve and the correlation between them reached a significant level as well. The theoretical fertilization depth that obtained the highest yield was 12.5 cm and 12.2 cm in 2013 and 2014, respectively. While in actual production, the DP15 treatment produced the highest yield with no significant difference between DP15 and DP10 treatment, with a significant increase of 16.72% and 16.50%, separately, compared with CK (P<0.05). Compared with DP0, nitrogen harvest index, partial nitrogen productivity, nitrogen agronomic efficiency and nitrogen utilization rate of summer maize all showed a trend of first increasing and then decreasing with the increase of basal fertilization depth. The agricultural efficiency of nitrogen fertilizer and the utilization rate of nitrogen fertilizer fit the quadratic curve. The nitrogen harvest index and nitrogen fertilizer agronomic efficiency were the largest under DP10 treatment in two years, achieving to 61.91% and 6.68 kg·kg-1, respectively, however, the highest nitrogen fertilizer efficiency was 47.27 kg·kg-1 and 46.97% under DP15 treatment, respectively. Compared with DP0, fertilization depth of 10 cm and 15 cm could increase soil nitrate and ammonium nitrogen content and reduce nitrogen loss. The mean value of nitrogen accumulation after flowering was 38.93% and 41.88% in 2013 and 2014, respectively, which promoted the post-flowering nitrogen accumulation and significantly increased the total nitrogen uptake above-ground by 20.45% and 22.36%, respectively. Correlation analysis showed that summer maize yield was significantly positively correlated with dry matter accumulation, total nitrogen accumulation, partial nitrogen productivity, nitrogen agronomic efficiency and nitrogen use efficiency, and significantly negatively correlated with nitrogen grain production efficiency.【Conclusion】 In nitrogen application rate of 225 kg N·hm-2, controlled release urea one-time basal application depth in 10 to 15 cm could significantly improve nitrogen absorption accumulation of summer maize, increase nitrogen use efficiency, reduce nitrogen loss, improve the dry matter accumulation, eventually obtain higher grain yield. Furthermore, it also realized higher production and efficiency, and could be used as controlled release urea suitable fertilization depth for summer maize sowing and manuring simultaneously.
【Objective】The objectives of this study were to discuss the effects of different organic-inorganic operation modes on crop yield, nitrogen efficiency and soil nutrients characteristics under the condition that wheat-maize straw returning to the field completely in two seasons, so as to provide a theoretical support for rational utilization of organic nutrient resources and scientific soil fertility culture in a wheat-maize cropping system.【Method】The experiment studied effects of different organic-inorganic operation modes on yield composition, nitrogen nutrient absorption, soil organic matter and stable aggregate, through designing the combination of chemical fertilizer with different amounts of organic fertilizer and straw-decomposing inoculant. Six experiment treatments were designed: F treatment was only chemical fertilizer, FA treatment was chemical fertilizer and straw-decomposing inoculants, FM1 treatment was chemical fertilizer and 1 500 kg·hm-2 organic fertilizer, FM2 treatment was chemical fertilizer and 3 000 kg·hm-2 organic fertilizer, FM3 treatment was chemical fertilizer and 4 500 kg·hm-2 organic fertilizer, FAM2 treatment was chemical fertilizer and 3 000 kg·hm-2 organic fertilizer and straw-decomposing inoculants.【Result】(1)Compared with single chemical fertilizer, application organic fertilizer and straw-decomposing inoculant could significantly increase grain yield of wheat-maize. The yield of chemical fertilizer combined with 4 500 kg·hm-2 organic fertilizer was the highest, wheat increased by 20.6%, maize by 10.6%. Combined chemical fertilizer with 3 000 kg·hm-2 organic fertilizer and straw-decomposing inoculant, the yield of wheat and maize increased by 19.5% and 8.2%, respectively. The increase of yield was due to the synergistic improvement of various components. The number of ears and grains per ear of wheat increased significantly and the number of grains per row increased most significantly in maize. (2) The increasing of organic fertilizer and straw-decomposing inoculant could promote the migration of nitrogen to the grain, improve the nitrogen harvest index, and increase the nitrogen accumulation in wheat and maize. The nitrogen accumulation and harvest index for both of FM3 treatment (application with 4 500 kg·hm-2 organic fertilizer) and FAM2 treatment (application with 3 000 kg·hm-2 organic fertilizer and straw-decomposing inoculant) were significantly higher than F treatment with single application of chemical fertilizer. Compared the treatment with non-bacterial, the NPFP of FA and FAM2 treatments that combined with straw-decomposing inoculant increased by 1.3-1.6 kg·kg-1. (3) The content of total nitrogen, alkali-hydrolyzed nitrogen and organic matter in the soil were significantly increased by increasing the organic fertilizer and straw-decomposing inoculant. The content of total nitrogen and organic matter in soil of FM3 treatment was the highest, and the annual total nitrogen increased by 0.17 g·kg-1 and the organic matter increased by 1.97 g·kg-1 compared with F treatment after two years. Different organic and inorganic application modes significantly reduced soil bulk density and increased soil porosity and water-stable aggregates. 【Conclusion】By two years field experiments, the application of organic fertilizer and straw-decomposing inoculant could increase the yield of wheat and maize, promote nitrogen absorption and transport, and improve soil structure and soil fertility. Under the conditions of this experiment, FAM2 treatment was recommended as an effective fertilization technology model for wheat-maize rotation in this region.
【Objective】This study was aimed to identify the effects of nitrogen application rates on grain yield, assimilate accumulation and translocation, physiological basis of winter wheat under the condition of high temperature stress, so as to provide technical and theoretical support for stress-resistance and stable yield cultivation.【Method】 Field experiments were conducted at Ji’nan experiment station and Jiyang experiment station of Crop Research Institute, Shandong Academy of Agricultural Sciences in 2018 and 2019, designed with two temperature treatments (CK: Control, H: High temperature stress) and three nitrogen levels (N1:Low nitrogen with 180 kg·hm-2, N2: Regular nitrogen with 240 kg·hm-2, and N3: High nitrogen with 300 kg·hm-2) . By analyzing assimilate accumulation, allocation, sucrose synthetase activity in leaf and grain, and grain yield with winter wheat cultivar JM44, the regulation of nitrogen application rates on grain yield of wheat under high temperature stress circumstances was studied. 【Result】 The results showed that grain yield decreased significantly under high temperature stress conditions, and grain yield reduction at N1, N2, and N3 were 54.78%, 24.05%, 54.49% and 50.19%, 25.29%, 44.13% in Ji’nan and Jiyang, respectively. Significant increases were noticed in assimilate accumulation amount, pre-anthesis assimilate translocation amount and rate to grain yield, post-anthesis assimilate accumulation amount and rate, ratio of grain to other organs udner N2 treatment, compared with N1 and N3 treatment, same as in SPAD value, sucrose synthetase-I activity (direction of synthetic) in flag leaf, and sucrose synthetase-Ⅱ activity (direction of decomposition) in grain. 【Conclusion】Higher grain yield could be achieved after high temperature stress during grain-filling stages with nitrogen application rate of 240 kg·hm-2, which could postpone flag leaf senescence, maintain high sucrose synthetase-I activity in flag leaf and sucrose synthetase-Ⅱ activity in grain, and keep high ability cof assimilate accumulate and transport to grain.
【Objective】This study was aimed to determine the suitable range and the drought stress thresholds of soil water on summer maize in Shandong Province, and to evaluate the effects of different drought degrees on growth and development and yield formation of summer maize quantitatively. So as to provide a basis for improving the utilization efficiency of agricultural water resources and alleviating the adverse impacts of drought stress. 【Method】Based on the data from field experiments, the suitable and unsuitable ranges of soil moisture were determined for the seedling stage, ear stage and grain stage of summer maize. By the model of WOFOST, the drought stress thresholds were analyzed with the relative water content as the driving factor. And the drought effects were assessed quantitatively through different drought degrees and their duration days. 【Result】(1) The suitable ranges of soil water during seedling stage, ear stage and grain stage of summer maize were 62%-91%, 66%-92% and 68%-94%, respectively. And the unsuitable ranges were less than 62%, 66% and 68%, respectively. (2) The thresholds of no drought, light drought, medium drought and severe drought during seedling stage were 53%, 50%, 45% and 40%, respectively. The thresholds of different drought degrees during ear stage were 58%, 48%, 43% and 37%, respectively. The thresholds of different drought degrees during grain stage were 57%, 52%, 49% and 45%, respectively. (3) The drought happened during seedling stage had the greatest effects on the total leaf weight, total stem weight and maximum leaf area index. The drought happened during ear stage and grain stage had the greatest effects on the total ear weight. And the severe drought during ear stage would result in the failure of final yield formation. 【Conclusion】The suitable ranges of soil water and the drought thresholds of summer maize were brought to light in Shandong. The drought happened during ear stage and grain stage of summer maize had more significant impacts on yield formation.
【Objective】In order to achieve synergistic promotion of both maize grain yield and nitrogen use efficiency (NUE) under salt stress, it is essential to explore the performance difference of different salt-tolerant maize varieties on yield formation, nitrogen uptake, transport and utilization, to excavate biological potential of maize varieties using nitrogen, so as to provide matched maize variety for the optimized nitrogen application regime.【Method】In this study, salt-tolerance maize varieties Denghai605, Ludan818 and salt-sensitive maize varieties Ludan981 and Liansheng188 were separately used to systematically study the effects on accumulation and distribution of dry matter and nitrogen, nitrogen utilization efficiency and yield formation under different nitrogen application rates of 0, 180 and 360 kg·hm-2, denoted by N0, N1 and N2 treatments in turn, as well as the interaction of nitrogen levels and maize varieties and inter-annual were analyzed.【Result】Suitable nitrogen application rate could significantly increase grain yield. Compared with N1 treatment, there were no difference in grain yield for salt-tolerance varieties but significant increase for Ludan981 (avg. 9.93%) and Liansheng188 (avg. 16.31%) under N2 treatment. Also, high nitrogen application (N2) got lower nitrogen agricultural efficiency (NAE), nitrogen utilization efficiency (NUE) and nitrogen partial factor productivity (NPFP) than low nitrogen application (N1). The difference in grain yield and yield components was the result from the varieties, nitrogen regimes, and their interaction. Compared with salt-sensitive maize varieties, salt-tolerance maize varieties had greater grain yield, nitrogen absorption and use efficiency across same nitrogen regime. Specifically, the grain yield of salt-tolerance maize varieties were increased by 7.78%-27.63% (N0), 7.40%-24.87% (N1), and 0.32%-9.55% (N2), respectively, while the nitrogen utilization efficiency were increased by 26.65%-48.28% (N1) and 1.20%-24.87% (N2), respectively.【Conclusion】It was performance well for the salt-tolerances varieties than the salt-sensitive varieties on dry matter accumulation and nitrogen uptake and utilization. Low nitrogen application was beneficial for salt-tolerant maize variety getting higher grain yield and vice versa. The nitrogen utilization efficiency was affected by maize varieties, nitrogen regimes and its interaction, through affecting grain yield, dry matter accumulation, and nitrogen uptake and utilization. Thus, it would be an efficient strategy to achieve synergistic promotion of both maize grain yield and nitrogen use efficiency, through the coordination of nitrogen optimization with matched maize variety.
【Objective】The purpose of this experiment was to explore the effects of different spring nitrogen topdressing modes on stem lodging resistance, lignin accumulation, grain yield of winter wheat, and to identify the appropriate spring nitrogen topdressing modes under the condition of high nitrogen application, so as to provide technical support for high and stable yield and stress-resistant cultivation of winter wheat.【Method】In the two wheat growing seasons of 2017-2018 and 2018-2019, the lodging sensitive variety Shannong 16 and the lodging resistant variety Jimai 22 were used as test materials, and the application rate was 1/3 under high nitrogen application rate of 300 kg·hm-2. There were four types of spring topdressing modes, which were equal amount of secondary nitrogen topdressing and remaining one-time nitrogen topdressing, namely the rising stage﹕booting stage 1/3﹕1/3 (T1), jointing stage: flowering stage 1/3﹕1/3 (T2), the remaining 2/3 nitrogen was applied at the booting stage (T3) and the remaining 2/3 nitrogen was applied at the jointing stage (CK). The effects of different nitrogen topdressing modes on stem resistance, lignin accumulation, expressive abundance of the key genes involving in lignin biosynthesis pathway and grain yield of winter wheat were studied.【Result】The total lignin accumulation and lignin monomers content of the lodging resistance wheat were both higher than those of the lodging sensitive wheat. The breaking strength under T1, CK was higher than that under T2 and T3, the lignin accumulation and monomer content were T1>T3>CK>T2 in two types cultivar, and the breaking strength, lignin accumulation, monomer content under all treatments at grain filling stage and maturity stage were T1>T3>T2>CK in two types cultivar. The breaking strength of Shannong 16 and Jimai 22 under T1 treatment were increased by 24.69%, 19.97%, 13.15% and 26.92%, 15.36%, 5.87%, respectively, compared with CK, T2, T3 at grain filling stage. The average lignin accumulation of Shannong 16 and Jimai22 under T1 at each growth stage was 21.71%, 15.45% , 8.85% and 25.19%, 21.75%, 15.83% higher than CK, T2, and T3, respectively. The average content of S monomer was 18.82%, 18.48%, and 8.39% higher than CK, T2 and T3 at maturity stage, respectively. The expressive abundance of key genes involved in lignin biosynthesis pathway (phenylalanine ammonia-lyase: PAL, caffeic acid3-o-methytransferase: COMT, coumarate-3-hydroxyl oxidase: C3H, innamoyl Co A reductase: CCR, cinnamate 4-hydroxylase: C4H etc.) decreased with the growth process, that tended to T1>T3>T2>CK under different stage of growth. The 1000-grain weight of the nitrogen topdressing remaining one-time at booting stage was higher than other treatments. T1 treatment could increase the spike number, grain number and yield. The lignin accumulation and monomer content of stem in different internodes during the same stage were I1>I2>I3>I4>I5.【Conclusion】Under the condition of high nitrogen application rate of 300 kg·hm-2 and basal application rate of 1/3, the same amount of secondary nitrogen topdressing modes treatment at the rising stage and booting stages significantly improved the breaking strength, lignin accumulation, lignin monomer content, the expressive abundance of key genes involved in lignin biosynthesis pathway and yield after anthesis stage, compared with other spring nitrogen topdressing modes. Therefore, the same amount of secondary nitrogen topdressing mode at rising stage and booting stage could be used as an appropriate spring nitrogen topdressing mode under the condition of high nitrogen application rate of 300 kg·hm-2 and basal application rate of 1/3 in Huang-Huai-Hai plain.
【Objective】In order to provide scientific grounds for the implementation of grain crop straw return, this study quantified the yield effect of straw return.【Method】It was collected and sorted out the published Chinese literatures in the past 30 years (a total of 274 piece of literature and 1 930 pairs data until December 31, 2019). By using meta-analysis method, the comprehensive effect of straw returning on crop yield was clarified with the main analysis process, included calculation of effect value, heterogeneity test, meta-subgroup analysis and publication bias test. And then, the effects under different experiment region, average annual temperature, average annual precipitation, soil texture, soil pH, crop type, planting system, tillage method, fertilization method, experiment duration and return amount was further quantitatively analyzed.【Result】Compared with straw remove, straw return significantly increased crop yield, and the average increasing rate was about 8.06%, with a 95% confidence interval of 7.52%-8.60%. No publication bias was found in the result. The yield effect was the highest in the southeastern region, reaching 9.37% (95% CI: 8.11%-10.64%). The straw-return effect was higher when the average annual temperature was 5-10 °C and the average annual precipitation is more than 1 200 mm. In different soil texture, the yield effect of straw return was 8.13% in clay (95% CI: 6.80%-9.49%), 9.04% in loam (95% CI: 8.06%-10.01%) and 6.96% in sandy soils (95% CI: 5.18%-8.77%), respectively. Among the three types of grain crops, namely, wheat, corn, and rice, the increase rate of yield on maize reached 9.22% (95% CI: 8.38%-10.05%) by straw returning. Plowing and no-till was the best tillage methods exerting the yield effect of straw returning, the increasing rate of yield were 11.05% (95% CI: 10.05%-12.05%) and 8.98% (95% CI: 7.21%-10.79%), respectively. When the straw was returned to the field without fertilization, the crop yield was significantly increased with an increase rate of 25.66% (95% CI: 22.04%-29.38%), which was significantly higher than that of 8.08% (95% CI: 7.50%-8.68%) under normal fertilization, but the overall yield level was lower. The yield increase rate of straw mulching reached 9.56% and the yield increase effect of straw mulching over 20 years was significantly increased (yield increase rate: 15.42%, 95% CI: 11.05%-19.95%). In addition, the most suitable amount of straw was half of the ex-crop (increase rate of yield was 9.09%, 95% CI: 7.41%-10.79%).【Conclusion】Straw return could significantly increase crop yield in different agricultural production areas. Furthermore, the long-term implication of crop straw with no-till or plowing tillage, normal fertilization and appropriate amount, could maintain continuous increase in crop yield.
