河西地区豆禾混播草地生产性能对刈割高度与施肥的响应

Herbage production and forage quality responses to cutting height and fertilization of legume-grass mixtures in the Hexi region

刈割和施肥是豆禾混播草地生产过程中极为重要的田间管理措施,合理的留茬高度和氮磷配施模式可以有效提高混播草地的生产性能。为探究不同留茬高度和施肥模式对多年生豆禾混播草地产量与品质的影响,在河西走廊地区以紫花苜蓿、无芒雀麦和长穗偃麦草1∶1∶1建植的第3年豆禾混播草地为试验对象,利用裂区试验设计,以留茬高度为主区,设置5 cm(A_(1))、8 cm(A_(2))、11 cm(A_(3))3个留茬高度,施肥模式为副区,设置不施肥CK(B_(1))、单施磷肥:150 kg P_(2)O_(5)·hm^(-2)(B_(2))、低氮高磷:75 kg N·hm^(-2)+225 kg P_(2)O_(5)·hm^(-2)(B_(3))、氮磷平衡:150 kg N·hm^(-2)+150 kg P_(2)O_(5)·hm^(-2)(B_(4))、单施氮肥:150 kg N·hm^(-2)(B_5)、高氮低磷:225 kg N·hm^(-2)+75 kg P_(2)O_(5)·hm^(-2)(B_(6))6个施肥模式,在混播草地中豆科牧草初花期进行刈割,施肥方式为第1茬刈割后追施。结果表明:以A_(3)B_(3)(11 cm留茬高度和75 kg N·hm^(-2)+225 kg P_(2)O_(5)·hm^(-2)的施肥模式)处理组合全年产量最高(19626 kg·hm^(-2));A_(2)B_(2)(8 cm留茬高度和150 kg P_(2)O_(5)·hm^(-2)的施肥模式)处理组合全年产量最低(14342 kg·hm^(-2))。提高留茬高度会在一定程度上降低紫花苜蓿整体品质,提高禾本科牧草整体品质。增施氮肥的同时减施磷肥可有效提高牧草粗蛋白含量和相对饲用价值(RFV),施用量过高会使牧草粗蛋白含量和相对饲用价值下降,最合理的氮磷配施模式为150 kg N·hm^(-2)+150 kg P_(2)O_(5)·hm^(-2)。综合产量和品质的结果来看,适当的磷肥施用量可以显著提高牧草营养品质。利用TOPSIS综合评价模型对混播草地产量及各混播组分营养品质进行整体评价后得出:8 cm的留茬高度以及施150 kg N·hm^(-2)+150 kg P_(2)O_(5)·hm^(-2)的氮磷为适宜在河西走廊地区紫花苜蓿+无芒雀麦+长穗偃麦草混播草地利用的留茬高度与施肥模式的组合。

Mowing and fertilization are extremely important field management decisions in the cultivation of legumegrass mixtures.Appropriate stubble height at mowing and optimal application rates of nitrogen and phosphorus fertilizers can enhance the productivity of mixed grassland.This research was conducted in the Hexi Corridor area and explored the effects of different stubble heights and fertilizer application rates on the yield and quality of a threeyear-old perennial legume-grass mixture comprising Medicago sativa,Bromus inermis and Elytrigia elongata at a planting ratio of 1∶1∶1.The experiment used a split-plot design with three stubble heights as main plots:5 cm(A_(1)),8 cm(A_(2))and 11 cm(A_(3)).Six fertilizer treatments were included as sub-plots:no fertilization(CK,B_(1)),single phosphorus(150 kg P_(2)O_(5)·ha^(-1),B_(2)),low nitrogen and high phosphorus(75 kg N·ha^(-1)+225 kg P_(2)O_(5)·ha^(-1),B_(3)),equal nitrogen and phosphorus(150 kg N·ha^(-1)+150 kg P_(2)O_(5)·ha^(-1),B_(4)),single nitrogen application(150 kg N·ha^(-1),B5),high nitrogen and low phosphorus application(225 kg N·ha^(-1)+75 kg P_(2)O_(5)·ha^(-1),B_(6)).The leguminous forages in the mixed grassland were mowed at the early-flowering stage,and fertilized after the first mowing.It was found that:the A_(3)B_(3)treatment combination had the highest annual yield(19626 kg·ha^(-1));and the A_(2)B_(2)treatment combination had the lowest annual yield(14342 kg·ha^(-1)).Increasing the stubble height reduced the crude protein content of alfalfa to some extent,and adding nitrogen enhanced the crude protein levels of poaceous forages.The relative forage value(RFV)of herbage was increased by increasing nitrogen and decreasing phosphorus,and the forage RFV was also decreased when the fertilizer application rate was too high.The optimal combination of nitrogen and phosphorus fertilizer was 150 kg N·ha^(-1)+150 kg P_(2)O_(5)·ha^(-1).Based on the combined results for yield and quality,the appropriate application rate of phosphate fertilizer application significantly improved the nutritional quality of forage grass.Using the TOPSIS comprehensive evaluation model to evaluate the yield of mixed grassland and the nutritional quality of each mixed forage,the 8 cm stubble height and 150 kg N·ha^(-1)+150 kg P_(2)O_(5)·ha^(-1)is the optimal combination of stubble height and fertilizer application for the mixed forage cropping of M.sativa+B.inermis+E.elongata in the Hexi Corridor.