水氮耦合对无芒雀麦产量及氮磷钾化学计量特征的影响

Effects of optimal irrigation and nitrogen coupling on Bromus inermis yield,nitrogen,phosphorus,and potassium stoichiometric characteristics

【目的】合理的水分和养分供给是保障人工草地高效可持续生产的有效措施。探究不同灌溉量和施氮量及其交互作用对牧草产量及养分含量的影响,有助于深入了解牧草生长对草地生态系统的响应。【方法】以人工种植无芒雀麦(Bromus inermis)为研究对象进行田间试验。采用喷灌方法,在无芒雀麦拔节期按照田间持水量(θ_(f))范围设置4个灌溉水平:75%~85%θ_(f)(W_(0))、45%~85%θ_(f)(W_(1))、55%~85%θ_(f)(W_(2))、65%~85%θ_(f)(W_(3));每个灌溉水平下分别设置0、60、120和180 kg/hm^(2)4个施氮水平,依次记为N_(0)、N_(1)、N_(2)和N_(3),共16个水氮组合。作物共刈割3次,调查每次刈割的干物质量和氮(N)、磷(P)、钾(K)含量及其化学计量特征。【结果】水分补偿和施用氮肥分别提高了无芒雀麦总产量22.0%~58.1%和31.1%~88.9%,两者对无芒雀麦总产量的交互作用也达到极显著水平(P<0.01)。16个水氮组合中,N_(1)W_(2)、N_(2)W_(3)和N_(3)W_(0)较N_(0)W_(1)组合的产量分别提高66.6%、158.0%和144.7%,以N_(2)W_(3)的产量最高(12260 kg/hm^(2)),其余的组合处理产量显著低于N_(2)W_(3)。回归分析表明,施氮和灌水分别为152.3 kg/hm^(2)和552.1 mm时,产量达到峰值13308 kg/hm^(2)。水分补偿显著提高无芒雀麦N、P、K含量,施用氮肥显著增加无芒雀麦N、K含量,却降低P含量(P<0.01)。无芒雀麦N/P、K/P总体表现为随灌水量的增加先增加后减少(W_(0)水平最低)、随施氮量的增加而显著增加(N_(3)水平最高)的趋势(P<0.01),水分补偿和施用氮肥对N/K均无显著影响。水氮互作对无芒雀麦N、P、K含量、N/P、K/P及N/K等指标均无显著效应;回归分析发现,无芒雀麦N和K含量在施氮、灌水分别为136.8 kg/hm^(2)、546.3 mm和139.3 kg/hm^(2)、552.5 mm时达到最高,分别为23.6和23.1 mg/g;对于P含量,在现有试验范围内,无法寻求其阈值。【结论】水分补偿和施用氮肥对无芒雀麦提产增养效果明显,且后者较前者增产幅度大;水氮交互在短期内对无芒雀麦产量有显著耦合效应,而对氮磷钾化学计量特征无显著影响;水氮耦合效应可能与土壤干旱程度、施氮量及牧草生长时期有关;通过回归预测得出,河西走廊地区无芒雀麦适宜的水氮范围为灌水546.3~552.5 mm、施氮136.8~152.3 kg/hm^(2)。

【Objectives】Reasonable regulation of water and nitrogen effectively ensures artificial grassland's efficient and sustainable development.This study aimed to explore the appropriate combination of irrigation and nitrogen supply for the high yield and nutrient content of Bromus inermis and understand the response of the grassland ecosystem to the combined irrigation and nitrogen effect.【Methods】A field experiment was conducted in the artificial grassland in the Hexi Corridor region,taking Bromus inermis as the test material.We used sprinkler irrigation technology to compensate for the soil moisture content at the joining stage,corresponding to 75%-85%(W_(0)),45%-85%(W_(1)),55%-85%(W_(2)),and 65%-85%(W_(3))of field water capacity.Four N application rates of 0,60,120,and 180 kg/hm^(2)(N_(0),N_(1),N_(2)and N_(3))were set up under each soil moisture level,giving 16 irrigation and nitrogen combinations.The grasses were harvested three times to determine dry matter yield.The stoichiometric characteristics of nitrogen(N),phosphorus(P)and potassium(K)were recorded in each cut.【Results】Irrigation and N addition increased the total yield of Bromus inermis by 22.0%-58.1%and 31.1%-88.9%,respectively.The interaction of the two factors(P<0.01)affected Bromus inermis yield.Compared with N_(0)W_(1),N_(1)W_(2),N_(2)W_(3)and N_(3)W_(0)increased Bromus inermis yield by 66.6%,158%,and 144.7%,respectively,with the maximum yield recorded under N_(2)W_(3)treatment(12260 kg/hm^(2)).For a peak production of 13308 kg/hm^(2)Bromus inermis,regression analysis revealed that the N application rate and irrigation were 152.3 kg/hm^(2)and 552.1 mm,respectively.Water compensation increased the N,P,and K content of Bromus inermis.N addition(P<0.05)increased that of N and K but decreased P(P<0.01)content of Bromus inermis.The interaction of the factors imposed did not affect the N,P,and K content of Bromus inermis.The N/P and K/P ratios of Bromus inermis increased at first,then reduced as irrigation levels increased;N application rate enhanced the plant N/P and K/P ratios,but no interaction effect was found.Regression analysis showed that N and K contents reached the maximum(23.6 mg/g and 23.1 mg/g)at 136.8 kg/hm^(2),546.3 mm and 139.3 kg/hm^(2),552.5 mm,respectively.For P content,the threshold could not be determined within the test range adopted in this study.【Conclusions】Irrigation and N application could increase the yield and NPK contents of Bromus inermis.However,the N application rate had a greater yield increase effect than irrigation.Irrigation and N application had a coupling effect on the yield of Bromus inermis within a short period,but not N,P,and K stoichiometry.The coupling effect of irrigation and N may be related to soil drought degree,N application rate and grass growth period.According to the regression prediction,the suitable range of irrigation and N input for Bromus inermis in the Hexi region was 546.3-552.5 mm and 136.8-152.3 kg/hm^(2).