以优质丰产杂交中籼稻徽两优898和Y两优900为试验材料开展田间小区试验，钵苗机插条件下设置5个施氮量处理 (0、75、150、225、300 kg ha^-1)，利用不同生育时期水稻地上部干物质量累积和植株氮浓度构建钵苗机插杂交籼稻临界氮浓度稀释曲线，利用该曲线计算NNI和N_and诊断氮素营养状况，进而探究NNI 与N_and和相对产量（RY）的关系。施氮处理显著增加钵苗机插杂交籼稻地上部生物量和植株氮浓度（P<0.05），钵苗机插杂交籼稻临界氮浓度（N_c）与地上部生物量（DM）之间符合幂函数曲线N_c=4.02DM^-0.42（R²=0.97），模型RMSE 和n-RMSE 分别为0.23、10.61%，表明模型具有较好的准确性和稳定性。整个生育期内植株NNI 值范围为0.58~1.31，与之对应的N_and值为-55~109 kg ha^-1。各生育时期NNI与N_and的存在显著线性模型关系（0.53<R²<0.99，P<0.01），而NNI与RY间满足线性平台模型关系（0.73<R²<0.92，P<0.01）。本研究构建模型可用于诊断钵苗机插杂交籼稻氮素营养状况，为定量氮肥管理提供依据。

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 (P_R) resource and heat resource (P_H) for each ATZ under potential production from 1981 to 2017. Finally, we quantified the contributions of cultivar changings to yield, P_R and P_H 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. P_R and P_H 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, P_R and P_H 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.

于极端降雨量事件的频繁发生，涝渍胁迫已成为粮食生产的明显制约因素。叶片含水量是一个重要的指标，且高光谱遥感为测定它提供了一种无损、实时且可靠的方法。因此，本文基于盆栽试验，于拔节期对冬小麦进行不同涝渍胁迫梯度处理。涝渍胁迫后每7天采集一次叶片高光谱数据、叶片含水量（leaf water content, LWC）数据，直至小麦成熟。结合植被指数构建、相关分析、回归分析、BP神经网络（BP neural network, BPNN）等方法，我们发现：（1）涝渍胁迫对叶片含水量的影响具有滞后性。（2）所有涝渍胁迫均会导致叶片含水量的降低。重度渍水下叶片含水量的下降速度比轻度渍水快，但长期轻度渍水比短期重度渍水对叶片含水量的影响程度更深。（3）叶片含水量的光谱敏感波段位于可见光（VIS, 400-780 nm）和短波红外（SWIR, 1400-2500 nm）波段。（4）以648 nm处原始光谱值，500 nm处一阶微分值，红边位置，新植被指数RVI (437, 466), NDVI (437, 466) 和NDVI' (747, 1956) 作为自变量建立的BPNN模型最适合反演涝渍胁迫冬小麦叶片含水量（建模集：R2=0.889, RMSE=0.138；验模集：R2=0.891, RMSE=0.518）。研究结果对涝渍胁迫精确防控具有重要的理论意义和实际应用价值。

长期秸秆还田是提高农田土壤有机碳储量的重要碳源，秸秆焚烧还田在我国南方也屡见不鲜。然而，长期稻草管理对土壤有机碳组分、酶活性及其相互关系的影响，以及其影响是否存在季节差异却尚未明确。我们基于2009年开始建立的长期定位试验平台，通过设置3个N、P、K等养分输入(包括秸秆/灰分和化学养分)的处理：秸秆不还田(CK)、秸秆还田(SR)和秸秆焚烧还田(SBR)，探讨长期秸秆还田条件对南方双季稻田土壤有机碳组分及土壤酶活性的影响。结果表明，与CK相比，长期秸秆还田有利于提高早稻产量(P=0.057)，并显著增加早晚稻田土壤的总有机碳（TOC）和微生物量碳(MBC)含量。而稻草焚烧还田对TOC无显著影响，但降低了早稻轻组有机碳（LFOC）和晚稻易氧化有机碳(EOC)含量，而显著增加了可溶性有机碳（DOC），且显著降低了土壤pH。我们研究还表明，长期秸秆还田条件下，MBC是评估双季稻系统土壤有机碳变化最敏感的指标；此外，SBR和SR对土壤酶活性的影响早晚稻稻田土壤呈现相反趋势，进而导致土壤有机碳组分含量存在季节差异，尤其是改变了土壤DOC含量，而早晚稻DOC与β-木糖苷酶均呈正相关。可见，秸秆还田较秸秆焚烧还田更有利于土壤有机碳组分的固持与提高，但其对晚稻土壤酶活性的负作用有待进一步研究。

Direct-sowing establishment method has great significance in improving winter oilseed rape (Brassica napus L.) production and guaranteeing edible oil security in China. However, nutrient responses on direct sown winter oilseed rape (DOR) performance and population development dynamic are still not well understood. Therefore, five on-farm experiments were conducted in the reaches of the Yangtze River (RYR) to determine the effects of nitrogen (N), phosphorus (P), and potassium (K) deficiencies on population density, dry matter production, nutrient uptake, seed yield, and yield components of DOR plants. Four fertilization treatments included the balanced NPK application treatment (NPK, 180 kg N, 39.3 kg P, 100 kg K, and 1.8 kg borax ha–1) and three nutrient deficiency treatments based on the NPK treatment, i.e., –N, –P, and –K. The results indicated that DOR population density declined gradually throughout the growing season, especially at over-wintering and pod-development stages. Nutrient deficiency decreased nutrient concentration in DOR plants, limited dry matter production and nutrient uptake, and thereby exacerbated density reduction during plants growth. The poor individual growth and reduced population density together decreased seed yield in the nutrient deficiency treatment. Averaged across all the experiments, seed yield reduced 61% by N deficiency, 38.3% by P deficiency, and 14.4% by K deficiency. The negative effects of nutrient deficiency on DOR performances followed the order of –N>–P>–K, and the effects were various among different nutrient deficiencies. Although N deficiency improved DOR emergence, but it seriously limited dry matter production and nutrient uptake, which in turn led to substantial plants death and therefore resulted in a very low harvested density. The P deficiency significantly reduced initial density, limited plants growth, and exacerbated density reduction. The K deficiency mainly decreased individual growth and yield, but did not affect density dynamic. Our results highlighted the importance of balanced NPK application in DOR production, suggesting that management strategy of these nutrients should be comprehensively considered with an aim to build an appropriate population structure with balanced plant density and individual growth.

Hybrid indica rice (Oryza sativa L.) cultivars play an important role in rice production system due to its heterosis, resistance to environmental stress, large panicle, and high yield potential. However, no attention has been given to its root growth dynamic responses to rising atmospheric CO2 concentration ([CO2]) in conjunction with nitrogen (N) availability. Free air CO2 enrichment (FACE) and N have significant effects on rice root growth. In this experiment, a hybrid cultivar Shanyou 63 (Oryza sativa L.) was used to study the effects of FACE and N levels on roots growth of rice. The results showed a significant increase in both adventitious root volume (ARV) and adventitious root dry weight (ARD) under the FACE treatment. The application of nitrogen also increased ARV and ARD, but the increase was smaller than that under FACE treatment. On the basis of the FACE experiment, numerical models for rice adventitious root volume and dry weight were built with the time as the driving factor. The models illustrated the dynamic development of rice adventitious root volume and dry weight after transplanting, regulated either by the influence factor of atmospheric [CO2] or by N application. The models were successfully used to predict ARV and ARD under FACE treatment in a different year with the predicted data being closely related to the actual experimental data. The model had guiding significance to growth regulation of rice root under the condition of atmospheric [CO2] rising in the future.