沟垄集雨补灌下密度和施氮对青贮玉米产量品质及水氮利用的调控研究

Developing silage maize is one of the important farming practises that has been identified to respond to the national strategy of “converting grain to forge” and alleviating feed shortage in animal husbandry. It is of great value to study the high-yield, better-quality and high-benefit cultivation techniques of silage maize. The ridge-furrow rainfall harvesting (RFRH) system is one of the effective measures to improve forage yield and water utilization efficiency in semi-arid region. However, under the RFRH system, the understanding of effects of irrigation, plant density and nitrogen application on forage yield, forage quality and water-nitrogen utilization is poor and the mechanisms are not clear. This project is aimed to: 1) study the effects of supplementary irrigation, planting density and nitrogen application on dry matter accumulation, yield formation and forage quality of silage maize under the RFRH system. 2) analyse the vertical distribution of soil moisture, soil water storage dynamics and water consumption characteristics at different growth stages of silage maize. 3) clarify the relationship between nitrogen use efficiency and plant nitrogen uptake, soil nitrate profile distribution. 4) determine the physiological characteristics of silage maize to reveal the physiological mechanisms of plant density and nitrogen fertilizer regulating forage yield, quality and water-nitrogen use efficiency under the RFRH system with supplementary irrigation. This study can provide theoretical basis for high-yield silage maize cultivation and efficient utilization of water and fertilizer in semi-arid region.

大力发展青贮玉米是响应国家粮改饲战略、缓解畜牧业饲料短缺的重要措施之一，研究其高产、优质、高效的栽培技术具有重要的应用价值。沟垄集雨种植是半干旱区提高饲草产量和水分利用效率的有效措施之一，但是在该系统下灌水、密度和施氮对饲草产量、品质及其水氮利用的影响效应仍不确定，且影响机制尚不明晰。本项目将采用沟垄集雨种植，在该系统下研究补充灌溉、种植密度和施氮水平对青贮玉米干物质积累、产量形成及饲草品质的影响，分析田间土壤水分垂直分布、贮水量动态变化以及青贮玉米各生育时期的耗水特征，理清氮肥利用效率与植株氮素吸收、土壤硝态氮剖面分布之间的关系，并在此基础上通过测定青贮玉米的生理特性，揭示沟垄集雨补灌下密度和氮肥调控饲草产量、品质及水氮利用效率的生理机制。该研究可为半干旱区青贮玉米的高产栽培与水肥高效利用提供理论依据。

沟垄集雨系统已成为半干旱区实现节水农业发展的主要栽培措施之一，但在该系统结合补充灌溉下青贮玉米适宜的种植密度和施氮量尚不明确，且补充灌溉、密度和施氮对青贮玉米产量、品质及水氮利用的影响效应及作用机制仍不清晰。为此，本研究在沟垄集雨系统下采用裂区试验设计，设置2种灌水模式、3个种植密度和3种施氮水平，探究在沟垄集雨系统下补灌、密度和施氮对半干旱区青贮玉米产量、品质及生理特性的影响。主要结论有：1）与不灌溉相比，补灌处理显著提高了青贮玉米的鲜草、干草、粗蛋白和淀粉的产量以及水分利用效率（WUE）、氮肥偏生产力（PFPN）、氮肥农学效率（NAE）和氮肥利用效率（NUE）。原因主要是补灌处理提高了灌浆期玉米叶片的净光合速率（Pn）、气孔导度（Gs）、蒸腾速率（Tr）、可溶性蛋白含量以及硝酸还原酶（NR）、超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、核酮糖二磷酸（RuBP）羧化酶和磷酸烯醇式丙酮酸（PEP）羧化酶的活性，显著降低了胞间CO2浓度（Ci）和丙二醛含量。2）随着种植密度的增加，青贮玉米的鲜草、干草、粗蛋白和淀粉的产量以及WUE、PFPN、NAE和NUE显著增高，而粗蛋白、粗脂肪含量和相对饲用价值（RFV）逐渐降低，酸性洗涤纤维（ADF）和中性洗涤纤维（NDF）含量逐渐升高。3）施氮处理较不施氮显著提高了鲜草、干草、粗蛋白和淀粉的产量以及粗蛋白含量和RFV，且过量施氮较适量施氮不能进一步增产提质。主要是因为适量施氮提高了灌浆期玉米叶片的可溶性蛋白含量、Pn、Tr和Gs以及NR、CAT、SOD、RuBP羧化酶和PEP羧化酶的活性，降低了丙二醛含量和Ci。4）沟垄集雨补灌下9.0万株/公顷种植密度结合200千克/公顷施氮量获得了较高的干草产量、WUE和NUE，是一种半干旱区青贮玉米水氮高效利用的管理策略，研究结果可为青贮玉米高产栽培与资源高效利用提供理论支持。