水氮调控对苜蓿与无芒雀麦混播草地生长和辐射利用的影响

Effects of water and nitrogen regulation on growth and radiation utilization of alfalfa and Bromus inermis Leysis.mixed cropping grassland

针对我国内陆干旱区人工草地生产管理粗放及气候资源利用不充分等问题,探究合理的牧草种植与水氮供应模式,以充分挖掘区域牧草的生产潜力。采用3 a生(2018年播种)紫花苜蓿(简称‘苜蓿’)和无芒雀麦,分析种植模式(苜蓿与无芒雀麦混播,D1;无芒雀麦单播,D2)、施氮量(低氮量N1:60 kg·hm^(-2);高氮量N2:120 kg·hm^(-2))和灌水量(以灌水下限占田间持水量θ_(f)的百分比计,分枝期均充分灌水(75%~85%θ_(f)),现蕾和初花期轻度亏水W1:65%~75%θ_(f)、中度亏水W2:55%~65%θ_(f)、重度亏水W3:45%~55%θ_(f),灌水上限均为85%θ_(f))对牧草叶面积指数(LAI)、干物质累积量、累积截获光合有效辐射量(CIPAR)、辐射利用效率(RUE)、产量(Y)、耗水量(ET_(a))、水分利用效率(WUE)和氮肥偏生产力(PFP_(N))的影响。结果表明:(1)牧草LAI和干物质累积量均随灌水量和施氮量的增加呈增大趋势,随生育时期的推进,LAI先快速增大后缓慢增大或减小,干物质累积量量先快速增大后缓慢增大。(2)灌水和施氮均能促进牧草CIPAR增加,W1N2较W1N1处理增加6.38%,W1N1较W3N1处理增加15.82%;施氮量与牧草RUE呈正相关关系,灌水量与混播牧草RUE呈正相关关系,与单播牧草RUE则基本呈负相关关系。(3)灌水量和施氮量的增加可提升牧草产量,W1N2处理牧草产量最大,混播和单播分别为26050.73 kg·hm^(-2)和12186.10 kg·hm^(-2);灌水量的增加会减小水分利用效率,W1较其他处理减小2.05%~8.16%;施氮量的增加会减小氮肥偏生产力,N2较其他处理减小9.68%~46.42%。(4)混播牧草的LAI、干物质累积量、CIPAR、RUE、WUE和PFP_(N)较单播分别提高132.62%、112.93%、49.27%、45.34%、88.76%和111.55%。综上可知,苜蓿与无芒雀麦混播结合轻度亏水(现蕾和初花期灌水下限为65%~75%θ_(f))和较高的施氮量(120 kg·hm^(-2))可显著提升牧草生物量、光合辐射利用效率和水氮利用效率。

To solve the problems of extensive production management of artificial grassland and insufficient utilization of climatic resources in inland arid areas of China,a reasonable pattern of forage planting,water and nitrogen supply was employed to fully explore the production potential of regional forage.Triennial(sown in 2018)alfalfa(referred to as‘alfalfa’)and Bromus inermis Leysis.were used to analyze planting patterns(alfalfa and Bromus inermis Leysis.mixed:D1;Bromus inermis Leysis.single:D2),nitrogen application(low N1:60 kg·hm^(-2);high N2:120 kg·hm^(-2))and irrigation amount on forage leaf area index(LAI),dry matter accumulation,cumulative interception of photosynthetically active radiation(CIPAR),radiation use efficiency(RUE),yield(Y),water consumption(ET_(a))water use efficiency(WUE)and nitrogen partial factor productivity(PFP_(N)).The irrigation amount was measured using percentage of the lower limit of irrigation to the field water holding capacityθ_(f),with adequate irrigation(75%to 85%θ_(f))at the branching stage,mild water deficit W1 of 65%to 75%θ_(f),moderate water deficit W2 of 55%to 65%θ_(f),and severe water deficit W3 of 45%to 55%θ_(f) at the budding and first flowering stage,and the upper limit of irrigation was 85%θ_(f).The results showed that:(1)The LAI and dry matter accumulation of forage grass increased with the increase of irrigation and nitrogen application.With the advance of growth period,LAI increased rapidly first and then slowly increased or decreased.Dry matter accumulation increased rapidly first and then increased slowly.(2)Both irrigation and N application promoted the accumulation of photosynthetically active radiation interception in forage.Compared with W1N1 treatment,W1N2 increased by 6.38%,W1N1 increased by 15.82%when comparing with W3N1 treatment.And the amount of N application was positively correlated with the RUE of forage grass,and the amount of irrigation was positively correlated with the RUE of mixed forage grass,while the opposite was true for unicasted forage.(3)The increase of irrigation and nitrogen application increased forage yield.Of which W1N2 treatment reached the maximum forage yield,with mixed and unicasted yields of 26050.73 kg·hm^(-2) and 12186.10 kg·hm^(-2),respectively.While the increase of irrigation reduced water use efficiency,W1 was 2.05%to 8.16%smaller than other treatments.And the increase of nitrogen application reduced the partial productivity of nitrogen fertilizer,N2 was 9.68%to 46.42%smaller than other treatments.(4)Compared with Bromus inermis Leysis,respectively,the LAI,dry matter accumulation,CIPAR,RUE,WUE and PFP_(N) of mixed forage increased by 132.62%,112.93%,49.27%,45.34%,88.76%and 111.55%,respectively.Alfalfa mixed with Bromus inermis Leysis.combined with mild water deficit(lower limit of irrigation 65%~75%θ_(f))and higher N application(120 kg·hm^(-2))significantly improved forage biomass and radiation use efficiency.