覆膜和灌水量对农田水热动态和制种玉米生长的影响

覆膜和节水灌溉是我国西北旱区应对水资源短缺、提高作物水分生产率的主要措施。为了探索覆膜与灌溉制度对农田水热和制种玉米生长的综合影响,揭示农田耗水及水分利用效率的变化规律,于2017年在中国农业大学石羊河流域农业与生态节水试验站进行了制种玉米田间试验,设置覆膜与水分2个控制因素,覆膜分别为完全覆膜(M1)与不覆膜(M0)2个水平,水分设置W1、W2、W3、W4和W5 5个水平,分别为当地传统灌溉定额的100%、85%、70%、55%和40%,灌水方式为滴灌,共10个处理。结果表明:相同灌水条件下覆膜相对于不覆膜处理,可减少棵间蒸发,增高生育前期土壤温度,使株高和叶面积指数的增长速率高于不覆膜,提前7~10 d达峰值,增产达6.5%~44.6%,水分利用效率提高16.9%~50.4%。但覆膜可阻滞降雨入渗,以单次典型降雨32.4 mm为例,覆膜较不覆膜降雨入渗百分比降低22.4%。相同覆膜条件下,土壤贮水消耗量随着灌水量的减少而增多,因此土壤贮水量随着灌水量的增加而增加。灌水量越多,制种玉米株高、叶面积指数和最终干物质累积量越高,而水分利用效率则越低。覆膜条件下,W1处理产量最高,W3次之,且两者之间无显著性差异,水分利用效率则为W5处理最高,W3次之。M1W3处理可以在保证较高产量的同时,水分利用效率较MIW1提高17.6%。综上,在当地制种玉米生产中,虽然覆膜可能减少地表降水入渗,但可以使生育期提前、减少棵间蒸发,对于节水增产有一定的促进作用。     

Time lag characteristics of sap flow in seed-maize and their implications for modeling transpiration in an arid region of Northwest China

Plant capacity for water storage leads to time lags between basal stem sap flow and transpiration in various woody plants. Internal water storage depends on the sizes of woody plants. However, the changes and its influencing factors in time lags of basal stem flow during the development of herbaceous plants including crops remain unclear. A field experiment was conducted in an arid region of Northwest China to examine the time lag characteristics of sap flow in seed-maize and to calibrate the transpiration modeling. Cross-correlation analysis was used to estimate the time lags between stem sap flow and meteorological driving factors including solar radiation(R_s) and vapor pressure deficit of the air(VPD_(air)). Results indicate that the changes in seed-maize stem sap flow consistently lagged behind the changes in R_s and preceded the changes in VPD_(air) both on hourly and daily scales, suggesting that light-mediated stomatal closures drove sap flow responses. The time lag in the maize's sap flow differed significantly during different growth stages and the difference was potentially due to developmental changes in capacitance tissue and/or xylem during ontogenesis. The time lags between stem sap flow and R_s in both female plants and male plants corresponded to plant use of stored water and were independent of total plant water use. Time lags of sap flow were always longer in male plants than in female plants. Theoretically, dry soil may decrease the speed by which sap flow adjusts ahead of shifts in VPD_(air) in comparison with wet soil and also increase the speed by which sap flow adjusts to R_s. However, sap flow lags that were associated with R_s before irrigation and after irrigation in female plants did not shift. Time series analysis method provided better results for simulating seed-maize sap flow with advantages of allowing for fewer variables to be included. This approach would be helpful in improving the accuracy of estimation for canopy transpiration and conductance using meteorological measurements.     

覆膜和灌水处理下土壤水分动态与玉米生长模拟研究

采用作物模型模拟作物生长过程和产量,是应对气候变化和人类活动的影响、实现农业节水增产的重要途径。覆膜和节水灌溉技术在我国西北旱区农田应用广泛,本研究基于覆膜增温对气积温的补偿效应以及覆膜和冠层截留对降雨入渗的影响对Aqua Crop模型进行了改进,使其适用于我国西北旱区覆膜制种玉米的模拟。利用2017年石羊河流域制种玉米的实测数据对改进模型进行了率定与验证,并模拟预测了未来气温升高和覆膜比变化情景下作物产量及水分利用效率(WUE)的变化规律。结果表明:改进的Aqua Crop模型能很好地模拟制种玉米生长发育阶段和冠层覆盖率,各处理冠层覆盖率的模拟值与实测值之间的R~2均不小于0.95,RMSE为3.9%~10.1%,NRMSE为4.9%~15.3%。而在1m土层贮水量的模拟上,各处理R~2在0.60~0.92之间,RMSE在9.5~17.1 mm之间,NRMSE处于4.4%~8.9%之间。改进的Aqua Crop模型在模拟不覆膜高水M0W1和M0W3处理的制种玉米干物质累积量、产量上模拟效果较差,其他处理的干物质累积量的R~2不小于0.98,RMSE为0.64~1.66 t/hm~2,NRMSE为9.9%~16.7%,产量的相对误差(RE)为-13.3%~4.5%,WUE则表现为除M0W1处理外,其他处理模拟效果较优,RE为-23.9%~18.1%。未来气温升高对作物产量及提高水分利用效率产生不利的影响。覆膜条件下,增温1.6℃和3.3℃分别比在实际温度下减产12.8%和20.7%,WUE降低3.0%和2.1%。不覆膜条件下减产率分别为13.9%和25.1%,WUE分别降低3.8%和7.6%。覆膜比例为50%时,可在保证产量的同时,提高水分利用效率,达到增产节水的效果。     

覆膜和水分亏缺对制种玉米灌浆期气体交换参数及产量的影响

为了揭示西北干旱地区水分亏缺条件下,覆膜对灌浆期玉米叶片光合生理特征及产量的影响规律,于2017年在中国农业大学石羊河流域农业与生态节水试验站进行了大田试验,设置2种覆膜方式(覆膜滴灌M1和不覆膜滴灌M0)和5种灌水处理(W1-W5),共10个处理.试验结果表明:在处理W1和W2下,气孔限制是光合速率下降的主要原因;在处理W3下,不覆膜方式以非气孔限制为主,而覆膜方式气孔限制和非气孔限制可能同时存在;在处理W4和W5下,非气孔限制成为光合速率下降的主要原因.覆膜具有明显的增产效果,与不覆膜方式差异具有统计学意义,轻度水分胁迫可以提高玉米叶片的净光合速率,有利于玉米增产.综上所述,在西北干旱地区,水分亏缺条件下,覆膜能够提高玉米的产量和收获指数;轻度水分亏缺时,植物通过气孔限制进行水分调控,而重度水分亏缺时,非气孔限制成为光合速率下降的主要因素.     

Stem flow of seed-maize under alternate furrow irrigation and double-row ridge planting in an arid region of Northwest China

Maize is widely planted throughout the world and has the highest yield of all the cereal crops. The arid region of Northwest China has become the largest base for seed-maize production, but water shortage is the bottleneck for its long-term sustainability. Investigating the transpiration of seed-maize plants will offer valuable information for suitable planting and irrigation strategies in this arid area. In this study, stem flow was measured using a heat balance method under alternate furrow irrigation and double-row ridge planting. Meteorological factors, soil water content(θ), soil temperature(Ts) and leaf area(LA) were also monitored during 2012 and 2013. The diurnal stem flow and seasonal dynamics of maize plants in the zones of south side female parent(SFP), north side female parent(NFP) and male parent(MP) were investigated. The order of stem flow rate was: SFPMPNFP. The relationships between stem flow and influential factors during three growth stages at different time scales were analyzed. On an hourly scale, solar radiation(Rs) was the main driving factor of stem flow. The influence of air temperature(Ta) during the maturity stage was significantly higher than in other periods. On a daily scale, Rs was the main driving factor of stem flow during the heading stage. During the filling growth stage, the main driving factor of NFP and MP stem flow was RH and Ts, respectively. However, during the maturity stage, the environmental factors had no significant influence on seed-maize stem flow. For different seed-maize plants, the main influential factors were different in each of the three growing seasons. Therefore, we identified them to accurately model the FP and MP stem flow and applied precision irrigation under alternate partial root-zone furrow irrigation to analyze major factors affecting stem flow in different scales.     

覆膜和灌水量对制种玉米根系分布及产量的影响

为探究制种玉米根系分布及产量对滴灌条件下地膜覆盖和灌溉量的动态响应，该研究于2017年和2018年在中国西北旱区石羊河流域，以制种玉米"Ganxin 630"为供试作物，设置覆膜与灌溉水量2个控制因素，覆膜包括透明膜全覆盖（M1）和不覆膜（M0）2个水平，灌溉水量设置WF、WM和WL 3个水平（分别为灌溉需水量的100%、70%和40%），共6个处理，通过监测制种玉米生育期内的土壤水分、土壤温度、根长密度、地上干物质量和产量状况，分析不同覆膜和灌水量条件下土壤水热动态、制种玉米根长密度分布和产量的变化规律。结果表明，在相同覆膜条件下，0～60 cm土层含水量随灌溉量的增加而增加。覆膜可改善土壤水热条件，在充分灌溉下覆膜增加土壤贮水量，而亏缺灌溉下覆膜降低土壤贮水量。覆膜明显提升播种后75 d内的土壤温度，对播种后75 d之后的土壤温度没有影响。制种玉米各个生育期不同覆膜和灌水量处理下的根长密度均随着土层深度的加深而降低，播种后95 d时，86.3%～96.7%的根系分布在0～60 cm土层，其中土层深度0～30 cm和距离植株基部水平方向0～15 cm范围内的根长密度高于1.0 cm/cm3，此空间范围以外则低于1.0 cm/cm3。充分灌溉有利于浅层根系生长，而水分亏缺有利于深层根系生长，其中WL处理10 cm深度处的根长密度比WF处理在各个生育期低19.6%～32.5%，深层根长密度则高0.2%～41.9%，产量和地上生物量基本随灌溉量的增加而增加。覆膜10 cm深度处的根长密度比不覆膜在各灌水处理下高4.4%～69.2%，产量高24.9%。制种玉米地上干物质量、产量与播种后75和95 d的0～20 cm土层的根长密度的关系较为密切，相关系数分别达0.883、0.804以上，保证该阶段良好的土壤环境、促进根系生长对制种玉米的生长至关重要。该研究可为石羊河流域科学地进行灌溉和和覆膜管理提供理论依据。