宁夏地区地下滴灌水肥耦合对紫花苜蓿种子产量及构成因素的影响

为了研究宁夏地区滴灌条件下紫花苜蓿种子生产的最适合的灌水及施肥量，以‘甘农4号’为试验材料，采用双因素裂区试验设计，主区为4个灌水梯度（900、1350、1800和2250 m³·hm^-2），副区为5个肥料梯度（N-P₂O₅-K₂O：0-0-0、9-45-60、18-90-120、27-135-180和36-180-240 kg·hm^-2），分别对不同处理的苜蓿种子产量构成因素及种子产量进行测定。研究结果表明适当的灌水和施肥可以提高苜蓿种子产量，随着灌水量和施肥量的增加，苜蓿种子产量呈先增高后降低的趋势。灌水对苜蓿的小花数、花序数、结荚数、种子数、结荚率和千粒重有显著影响，经通径分析得出，花序数、生殖枝数、千粒重和结荚率对苜蓿种子产量的影响起主导作用。在灌水量为900 m³·hm^-2、施肥量为27-135-180 kg·hm^-2时，苜蓿种子产量、灌溉水分利用效率最高。通过回归寻优模型，得出在宁夏引黄灌区苜蓿种子生产中滴灌的最佳灌水量为2250 m³·hm^-2，在当地的土壤条件下最佳施肥量为：氮肥34.44 kg·hm^-2，磷肥172.68 kg·hm^-2，钾肥230.28 kg·hm^-2。

Effect of water and fertilizer coupling on seed yield and composition of alfalfa grown with underground drip irrigation in Ningxia

This study investigated the most suitable irrigation and fertilizer rates for alfalfa （Medicago sativa） seed yield under drip irrigation in Ningxia. The alfalfa cultivar used in the experiment was ‘Gannong No.4’ and the experiment was laid out in a two-factor split plot design. There were four irrigation rates （900， 1350， 1800 and 2250 m³·ha^-1） in the main plot treatments， and five fertilizer levels （N-P₂O₅-K₂O applied in proportions by weight 0-0-0， 9-45-60， 18-90-120， 27-135-180 and 36-180-240 kg·ha^-1， respectively）. The results showed that appropriate irrigation and fertilizer applications improved alfalfa seed yield. With successive increments in irrigation and fertilizer alfalfa seed yield initially increased and then decreased. Irrigation had a significant effect on the alfalfa floret number， number of inflorescences per plant， number of pods formed， seeds per pod， pod setting rate and thousand seed weight. A path coefficient analysis showed that the number of inflorescences per plant， reproductive branch number， thousand seed weight and pod setting rate had important determinants of the seed yield of alfalfa. Alfalfa seed yield and irrigation water use efficiency were the highest at an irrigation rate of 900 m³·ha^-1 and an N-P₂O₅-K₂O fertilizer rate of 27-135-180 kg·ha^-1. According to a regression optimization model， the optimal irrigation rate for alfalfa seed production in the Ningxia Yellow River irrigation area under local soil conditions was 2250 m³·ha^-1， and the optimal fertilizer amount was 34 kg·ha^-1 of nitrogen fertilizer， 172.68 kg·ha^-1 of phosphate fertilizer and 230.28 kg·ha^-1.