水氮耦合对微咸水膜下滴灌棉花光合特性及产量的影响

Effects of Water and Nitrogen Coupling on Photosynthetic Characteristics and Yield of Film Mulching Cotton under Brackish Water Drip Irrigation

为明确水氮耦合效应对微咸水膜下滴灌棉花光合作用、产量及水肥利用效率的影响,寻求、优化适合微咸水储量丰富地区的最佳水、氮区间。设置3个水平的灌溉定额:2500、3500、4500 m^(3)/hm^(2)(W1、W2、W3);4个水平的施氮量:100、200、300、400 kg/hm^(2)(纯N)(N1、N2、N3、N4)。结果表明:棉花光合参数、产量及水肥利用效率等指标水氮耦合效应极显著。灌溉定额增加,棉花产量(Y)、氮肥偏生产力(N_(PFP))先上升后下降,净光合速率(P_(n))、蒸腾速率(T_(r))、气孔导度(G_(s))增加,灌溉水利用效率(iWUE)和细胞间CO_(2)浓度(C_(i))减小。对P_(n)、T_(r)、G_(s)而言,W1、W2水平时,均为N2水平的促进作用最大;W3水平时,N3水平提高最明显。对棉花C_(i)来说,W1、W2水平下,均在N4水平处取得最大值;W3水平下,N1水平时得到最大值。对Y、iWUE而言,W1水平时,N2水平的促进作用最大;W2、W3水平时,均为N3水平提高最明显。对N_(PFP)来说,灌溉定额相同时,均为N1施氮量提升效果最显著,N4施氮量的抑制作用最大。棉花产量最大值、最小值分别出现在W2N3、W1N4处理,依次为6725.89 kg/hm^(2)、5045.54 kg/hm^(2),相对减少了24.98%。通过建立多元回归方程,结合归一化处理和空间分析方法得出,棉花Y和P_(n)同时大于等于相对值0.9时的最佳灌水施氮量为3335.08~3968.36 m^(3)/hm^(2)和273.83~344.73 kg/hm^(2)。

In order to clarify the effect of water and nitrogen coupling on photosynthesis,yield,and water and fertilizer utilization efficiency of film mulching cotton under brackish water drip irrigation,and find and optimize the best water and nitrogen interval which is suitable for areas with rich brackish water reserves.We set up three levels of irrigation quota including 2500,3500 and 4500 m3/hm^(2)(W1,W2 and W3),and four nitrogen application rates including 100,200,300 and 400 kg/hm^(2)(pure N)(N1,N2,N3 and N4).With the increase of irrigation quota,cotton yield(Y)and nitrogen partial productivity(N_(PFP))first increased and then decreased,and net photosynthetic rate(P_(n)),transpiration rate(T_(r))and pore conductivity(G_(s))increased.And irrigation water use efficiency(iWUE)and intercellular CO_(2) concentration(Ci)decreased.To P_(n),T_(r) and G_(s),at W1 and W2 levels,N2 level had the greatest promoting effect.At W3 level,N3 level increased most significantly.For cotton C_(i),at W1 and W2 levels,the maximum value was obtained at N4 level.At W3 level,the maximum value was obtained at N1 level.For Y and iWUE,the promoting effect of N2 level was the greatest at W1 level.At W2 and W3 levels,the level of N3 increased most significantly.For N_(PFP),when the irrigation quota was the same,the effect of N1 nitrogen application was the most significant,and the inhibition effect of N4 nitrogen application was the greatest.The maximum and minimum cotton yield appeared under W2N3 and W1N4 treatments,which were 6725.89 kg/hm^(2) and 5045.54 kg/hm^(2),respectively,with a relative decrease of 24.98%.By establishing multiple regression equations,combined with normalization and spatial analysis methods,when Y and P_(n) were both greater than or equal to a relative value of 0.9,the best irrigation nitrogen application rates were 3335.08-3968.36 m^(3)/hm^(2) and 273.83-344.73 kg/hm^(2).