基于临界氮浓度模型的日光温室甜椒氮营养诊断

临界氮浓度稀释曲线是诊断作物氮营养状况的有效手段。该研究基于2 a温室小区试验,以参考作物蒸发蒸腾量（reference crop evapotranspiration,ET0）为基准,设置4个灌溉水平（105%ET0、90%ET0、75%ET0、60%ET0）和4个氮素水平（300、225、150、75 kg/hm2）,构建和验证基于地上部生物量的甜椒在不同水分条件下的临界氮浓度稀释曲线经验模型。结果表明,植株氮素吸收量、地上部生物量、经济产量和水分利用效率（water use efficiency,WUE）随灌水量增加呈先增加后减小的趋势;灌溉水平75%ET0和90%ET0下,最优施氮量差异较小,且可获得较高经济产量和WUE,但经济产量和WUE不能同时达到最佳。75%ET0灌溉水平可获得高于90%ET0灌溉水平约11%的水分利用效率,且经济产量仅降低约3%,鉴于研究区水资源较短缺,灌水量75%ET0施氮量190 kg/hm2左右为最佳策略。该研究可为西北地区温室甜椒实时精准灌水施氮提供理论依据和技术支持。研究可为西北地区温室甜椒实时精准灌水施氮提供理论依据和技术支持。

Nutrition diagnosis for N in bell pepper based on critical nitrogen model in solar greenhouse

The unreasonable application of water and nitrogen significantly affects the growth and the yield of greenhouse vegetables in northwest China, which has raised the need to adjust the crop irrigation and nitrogen (N) fertilizer requirements. Based on the aboveground biomass, the assessment of crop N status is an effective approach to optimize N management in greenhouse vegetable production. The research was conducted in a sunlit, ventilated greenhouse at the Key Laboratory of Agricultural Soil and Water Engineering in Arid Areas, Ministry of Education, in Yangling District, Shanxi Province, during the spring-summer (April-July) seasons of 2014 and 2015. The site is located at 34°20′N, 108°04′E. There were 4 irrigation levels (W1: 105%ET0, W2: 90%ET0, W3: 75%ET0, and W4: 60%ET0, ET0 is reference crop evapotranspiration) and four nitrogen levels (N1: 300, N2: 225, N3: 150, and N4: 75 kg/hm2), resulting in a total of 16 treatments. The plant samples at different treatments were taken 8 times during the study periods, i.e.,33, 54, 62, 72, 81, 91, 101, and 112 days separately after being transplanted, which were used to measure the aboveground biomass and total nitrogen of bell peppers. The yields of bell pepper were measured during the harvesting time. Soil moisture was measured before transplanting and after harvest using the time domain reflectometry. Water use efficiency was calculated by water balance method. Results showed that the total N uptake, aboveground biomass, yield and water use efficiency (WUE) were affected by the irrigation levels. The diagnosis results of the greenhouse pepper’s nitrogen nutrition based on critical N model were the same between the model of nitrogen nutrition (NNI) and the model of N uptake. The optimal N fertilizer were between 150 and 225 kg/hm-2, but more closer to 225 kg/hm-2. The irrigation levels of 75%ET0and 90%ET0were more favorable to the increase in nitrogen nutrition uptake. The 2 irrigation levels economic yields were 34.14 and 35.33 t/hm2, and WUE were 17.07 and 15.30 kg/m3, respectively. However, the economic yield and WUE could not achieve optimal results at the same time. The aboveground biomasses of bell pepper at the 2 irrigation had no significant difference when the N application rate was more than 150 kg/hm2. The optimal N application rates were 194.00 and 192.69 kg/hm2based on the economic yield, while the optimal N application rates were 191.13 and 191.83 kg/hm2based on WUE. Considering the water shortage condition in the northwest China, the irrigation level of 75%ET0 (N fertilizer application rate of about 190 kg/hm2) was suggested to be optimal for greenhouse bell pepper production since it could save water by about 11%, while the economic yield only declined by about 3% compared with the irrigation level of 90%ET0. The study can provide theoretical basis and technical support for improving water and nitrogen management of greenhouse bell peppers in northwest China.