氮肥对非充分灌溉下棉花花铃期光合特性及产量的补偿作用

研究氮肥对非充分灌溉下棉花花铃期光合特性及产量的补偿作用及其机制,以期为干旱地区棉花水肥高效利用提供理论依据。以"新陆中54号"为试材,采用裂区试验设计,主区为总灌溉量2800 m~3 hm~(–2)(非充分灌溉)和3800 m~3 hm~(–2)(常规灌溉),副区为4个施氮(纯N)水平(0、150、300和450 kg hm~(–2))。同一氮肥处理下,非充分灌溉处理棉花花铃期叶面积指数(LAI)、净光合速率(P_n)、蒸腾速率(T_r)、单株光合产物积累与分配、单株结铃数、单铃重及籽棉产量均低于常规灌溉处理,但籽棉增产率和灌溉水生产力高于常规灌溉处理;同一灌溉量下,随着氮肥施用量的增加,棉花花铃期LAI和单株光合产物积累量先增后降,且表现为N450N300N150N0,T_r、P_n、单株光合产物向生殖器官分配比例、单株结铃数、单铃重、籽棉产量、籽棉增产率及灌溉水生产力均表现为N300N450N150N0;非充分灌溉下增施氮肥的补偿效果随着氮肥用量的增加呈先增加后下降的趋势,N300处理补偿效果最显著,与常规灌溉处理相比,补偿效应主要表现在棉花花铃期P_n平均提高10.9%,单株光合产物积累向生殖积累器官分配比例提高10.7%,单株结铃数、单铃重、籽棉增产率及灌溉水生产力分别提高5.0%、8.0%、7.1%和7.5%;氮肥对棉花花铃期光合特性及产量构成因素的影响大于水分。非充分灌溉下氮肥施用量为300 kg hm~(–2)时补偿效应最大,虽然在产量上有所下降,但从干旱地区农业缺水的现实考虑,可准确灌溉施肥,且籽棉产量较常规灌溉处理仅下降1.3%。因此,在南疆自然生态条件下,非充分灌溉下施氮300 kg hm~(–2)时棉花花铃期LAI、T_r、P_n及单株光合产物积累量适宜,向生殖器官转运补偿效果显著,具有最大的产量补偿作用,且节水26.3%。

Compensation Effect of Nitrogen Fertilizer on Photosynthetic Characteristics and Yield during Cotton Flowering Boll-setting Stage under Non-sufficient Drip Irrigation

Cotton cultivar ‘Xinluzhong 54’ was used to study the compensation effect of nitrogen fertilizer on photosynthetic characteristics and yield and its mechanism during cotton flowering boll-setting stage under non-sufficient drip irrigation, so as to provide a theoretical basis for the efficient use of water and fertilizer for cotton in arid area. Split plot experiment design was used, the main area included total drip irrigation amount of 2800 m ³ ha ^-1 (non-sufficient drip irrigation) and 3800 m ³ ha ^-1 (conventional drip irrigation), the secondary area had four nitrogen (pure N) levels (0, 150, 300, and 450 kg ha ^-1). Under the same nitrogen fertilizer treatment, the leaf area index (LAI) of cotton at flowering and boll-setting stage, net photosynthetic rate (P_n), transpiration rate (T_r), accumulation and allocation of photosynthate, boll number of single plant, single boll weight and seed cotton yield of non-sufficient drip irrigation treatment were lower than those of conventional drip irrigation treatment, while seed cotton yield rate and drip irrigation water productivity were higher. Under the same drip irrigation amount, with the increase of nitrogen fertilizer amount, LAI of cotton at flowering and boll-setting stage and photosynthate accumulation increased first and decreased then, showing a trend of N450>N300>N150>N0, and T_r, P_n, allocation proportion of photosynthate to reproductive organ, boll number of single plant, single boll weight, seed cotton yield, seed cotton yield rate and drip irrigation water productivity showed a trend of N300>N450>N150>N0. The compensation effect of increasing nitrogen fertilizer under non-sufficient drip irrigation condition increased first and decreased then with the increase of nitrogen fertilizer amount, the compensation effect of N300 treatment was most significant, P_n of cotton flowering and boll-setting stage P_n increased by 10.9% averagely, the allocation proportion of photosynthate translocated to reproductive organ increased by 10.7%, boll number of single plant, single boll weight, seed cotton yield rate and drip irrigation water productivity increased by 5.0%, 8.0%, 7.1%, and 7.5%, respectively. The influence of nitrogen fertilizer on photosynthetic characteristics and yield components of cotton at flowering and boll-setting stage was greater than that of water. The compensation effect was the maximum when nitrogen fertilizer increased to 300 kg ha ^-1 under non-sufficient drip irrigation condition, though the yield decreased by 1.3% compared with conventional drip irrigation treatment. Therefore, in natural ecological conditions of South Xinjiang, 300 kg ha ^-1 nitrogen application with non-sufficient drip irrigation is suitable for cotton at production with better, LAI, T_r, P_n and photosynthate accumulation and translocated compensation effect to reproductive organ, as well as the maximum yield compensation effect and water conservation of 26.3%.