不同水分条件下控释尿素对夏玉米产量和叶片衰老特性的影响

Effects of water conditions and controlled release urea on yield and leaf senescence physiological characteristics in summer maize

采用旱棚土柱试验,以郑单958为材料,研究不同水分处理(重度干旱胁迫W_1、轻度干旱胁迫W_2、正常水分条件W_3)和不同控释尿素施氮处理(N_0:不施氮肥;低氮N_1:施纯氮150 kg·hm^(-2);中氮N_2:施纯氮225 kg·hm^(-2);高氮N_3:施纯氮300 kg·hm^(-2))对夏玉米产量及叶片衰老特性的影响.结果表明:控释尿素与水分耦合对延缓叶片衰老、提高功能叶作用时间和效率以及提高产量方面存在显著互作效应.相同氮素条件下,随着土壤水分含量的增加,夏玉米叶面积指数(LAI)、穗位叶叶绿素含量及超氧化物歧化酶(SOD)活性、过氧化氢酶(CAT)活性、过氧化物酶(POD)活性均显著提高,可溶性蛋白含量增加,而丙二醛(MDA)含量显著降低,产量增加;相同水分条件下,随着施氮量的增加,夏玉米LAI、穗位叶叶绿素含量及各种保护酶活性均显著提高,可溶性蛋白含量增加,而MDA含量显著降低,产量也呈增加趋势.但处理W_3N_3、W_3N_2和W_2N_3之间差异不显著,且相对于其他处理,各项指标(MDA除外)均保持较高水平,MDA含量较低,表明控释尿素与水分的耦合效应有利于维持穗位叶功能,延缓叶片衰老,促进光合产物的生产,进而提高夏玉米产量.综合产量、叶面积指数、叶绿素含量和各种保护酶活性及MDA、可溶性蛋白含量,在土壤含水量为(75±5)%的田间持水量条件下(正常水分),控释尿素施氮量超过225 kg N·hm^(-2)后,继续增施氮肥不能持续提高花后叶片的保护酶活性,且导致保护酶活性下降加快,MDA含量显著升高,加速植株衰老,不利于氮素的高效利用;在土壤含水量为(55±5)%的田间持水量条件下,控释尿素施氮量在300kg N·hm^(-2)条件下水氮耦合效应最佳.

In an soil column experiment with Zhengdan 958 （ a summer maize cuhivar planted widely in China）, treatments of three water levels, severe water stress W1 which the soil moisture kept （ 35±5 ） % of the field capacity, mild water stress W2 which was （55±5） %, normal water W3 which was （75±5）%, and four levels of controlled release urea fertilizer （No, N1 was 150 kg N · hm-2, N2 was 225 kg N · hm-2 and N3 was 300 kg N · hm-2） were included to study the interactive effects of water and controlled release urea on yield and leaf senescence characteristics of summer maize. The results showed that the coupling of water and controlled release urea had significant effects on increasing yield, delaying the senescence and keeping the high efficiency of the functional leaves. Under the same nitrogen condition, yield, LAI, chlorophyll content and the activities of SOD, POD, CAT and soluble protein content in summer maize ear leaf were significantly increased with more water supplying, and the content of MDA decreased significantly. Under the condition of the same moisture, these indicators were also significantly increased with the increasing nitrogen application and MDA content was reduced significantly. However, these indicators （except MDA） of W3N3, W3N2 and W2N3 treatments were maintained at a higher level and the MDA content was lo- wer compared with other treatments despite the fact that there were no significant difference among these three treatments, which indicated that the interactive effects of water and controlled release urea had an important role in maintaining the function of ear leaf, delaying the leaf senescence, and was beneficial to the photosynthates production and obtaining higher yield of summer maize. Integra- ting the yield, LAI, chlorophyll content, various protective enzymes activity, MDA and soluble protein content, controlled release urea application rate of 225 kg N · hm-2was the best treatment as the soil moisture content was （75±5）% of field capacity. Continuous increase in the nitrogen appli- cation could not enhance the activities of protective enzymes, oppositely, it could cause the decline of protective enzymes activities and the increase of MDA content rapidly and speed up plants trans- lation to senescence, which was not conductive to the efficient use of nitrogen. We suggested that coupling controlled release urea application rate of 300 kg N · hm-2 with soil moisture content of （55±5） % of field capacity was optimum.