Effects of Water Regulation under Subsurface Drip Irrigation on Yield, Quality and Soil Environment of Alfalfa in Desert Irrigation District
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【Author in Chinese】 马彦麟；
【Author's Information】 甘肃农业大学， 农业水土工程， 2018， 硕士
【Abstract in Chinese】 针对荒漠灌区资源性缺水和水分利用效率不高,区域主要饲草经济作物紫花苜蓿单产、品质较低及荒漠化程度日趋加重等问题,在具有典型荒漠气候特征的甘肃河西荒漠灌区对紫花苜蓿分枝期、现蕾期和全生育期进行水分调控（土壤含水量占田间持水量百分比）35%45%（W0:重度水分调控）、45%55%（W1:中度水分调控）、55%65%（W2:轻度水分调控）、65%75%（W3:充分灌溉）试验研究,分析不同生育时期水分调控处理下苜蓿株高、茎粗及土壤水分、养分的变化规律,阐释生育时期干旱胁迫复水补偿效应,明确干草产量和品质对水分调控的响应关系,基于水分-品质-产量-效益多目标影响指标,采用灰色关联度分析方法,探明水分调控对苜蓿生产性能的影响,获得适宜荒漠灌区苜蓿生长的最佳水分调控模式,得到如下主要结论:（1）紫花苜蓿耗水量随灌溉量的增加而增加,苜蓿地土壤水分随水分调控程度的加重呈降低趋势,随土壤深度的加深呈先降低后增加趋势。全生育期轻度水分调控处理下不同土层土壤水分变化较小,且能保持土壤水分在苜蓿正常生长的范围内,有利于苜蓿生长和减少水分无效损失。不同土层土壤有机质、碱解氮、速效磷和速效钾随土层深度的加深呈降低趋势,pH无明显差异。水分对040cm土层土壤pH值、有机质、碱解氮、速效磷和速效钾含量影响显著,且随水分调控程度的减轻有机质和碱解氮含量呈增加趋势,pH值、速效磷和速效钾含量呈递减趋势;（2）生育期内平均株高、茎粗和干草产量随刈割茬次的增加而降低,表现为第2茬>第3茬,且随水分调控程度的减轻呈增加趋势。分枝期不同程度的水分胁迫在现蕾期复水后,株高和茎粗生长表现出一定的补偿效应,进而未引起显著减产,在分枝期轻度水分调控处理下两茬苜蓿干草产量分别为4589.59 kg·hm-2和3781.96 kg·hm-2,与CK处理差异不显著（P>0.05）。分枝期水分调控较现蕾期有利于苜蓿株高、茎粗的生长和产量的形成,在分枝期、现蕾期和全生育期轻度水分胁迫不会引起苜蓿株高显著降低。随水分调控程度的减轻干草产量水分利用效率降低,两茬苜蓿在全生育期重度水分调控A9处理下干草产量水分利用效率最高分别为3.47 kg·hm-2和2.96 kg·hm-2;（3）随刈割茬次的增加,茎叶比呈第2茬>第3茬,粗蛋白含量呈第2茬<第3茬,茎叶比和粗蛋白含量随水分调控程度的减轻呈先增加后减小的趋势。分枝期适度水分调控处理较现蕾期有利于苜蓿茎叶比的降低和粗蛋白含量的积累,两茬苜蓿在全生育期轻度水分调控处理下茎叶比最小分别为1.29和0.88,粗蛋白含量最高分别为21.08%和23.26%。与干草产量变化趋势相同,随刈割茬次的增加粗蛋白产量呈第2茬>第3茬,且随水分调控程度的减轻粗蛋白产量呈递增趋势。两茬苜蓿在分枝期轻度水分调控A3处理下粗蛋白产量最高分别为902.90kg·hm-2和825.26 kg·hm-2,但与全生育期轻度水分调控A7处理无显著差异,分枝期和全生育期轻度水分胁迫较现蕾期有利于粗蛋白产量的提高。随水分调控程度的减轻品质-水分利用效率基本也呈减小趋势,且分枝期较现蕾期有利于提高苜蓿品质-水分利用效率,与干草产量水分利用效率得出的结果基本一致,全生育期合理的水分调控有利于提高苜蓿品质-水分利用效率,第2、3茬苜蓿分别在全生育期重度水分调控和轻度水分调控处理下品质水分利用效率最高,分别为0.64 kg·m-3和0.55 kg·m-3;（4）随着刈割茬次的增加,粗脂肪和粗灰分含量增加、酸性洗涤纤维（ADF）和中性洗涤纤维（NDF）含量降低。随水分调控程度的减轻,粗脂肪和粗灰分含量呈递增趋势,ADF和NDF含量呈先减小后增加趋势,相对饲喂价值（RFV）呈先增加后降低趋势。现蕾期水分调控更有利于粗脂肪和粗灰分含量的提高,分枝期水分调控更有利于降低苜蓿ADF和NDF含量,提高RFV值。两茬次苜蓿在全生育期轻度水分调控处理下ADF和NDF含量最低,RFV值最大分别为169.32和223.48;（5）基于干草产量、干草和品质水分利用效率、粗蛋白产量及RFV等指标通过灰色关联分析方法综合分析得出,各指标对苜蓿生产性能的影响大小依次为:蛋白质产量>干草产量>品质水分利用效率>RFV>干草产量水分利用效率,且在A7处理下的加权关联度最大为0.8052,再依次为A2、A3、CK、A9、A8、A6、A1、A4、A5,分枝期较现蕾期进行水分调控有利于苜蓿生产性能的提高,在全生育期轻度水分调控处理下综合性状最好,是适宜当地苜蓿生长的最佳水分调控模式,有利于灌区苜蓿种植生产,实现高产优质和节水的目的。
【Abstract】 In view of the lack of water resources and water use efficiency（WUE）in desert irrigated areas,such as the low yield and poor quality of the alfalfa and the desertification is becoming more and more serious.This article studied different degrees of water regulation as 35%45%（W0:severe water regulation）,45%55%（W1:moderate water regulation）,55%65%（W2:light water regulation）,65%75%（W3:full irrigation）of field capacity in the alfalfa branching,bud period and full growth period at Gansu Hexi Desert irrigation area with typical desert climate characteristics.The changes of alfalfa plant height,stem diameter and soil moisture as well as nutrients were analyzed under different water control stages at different growth stages.The response of rehydration to drought stress and hay yield as well as quality of the alfalfa to water control during the period of drought stress was explained.The quality,yield,economic benefit,the effect of water regulation,etc.on the performance of alfalfa,based on the multi objective index of water,was analyzed by the grey correlation analysis method.And the key growth period of water control and the gradient of soil moisture control was selected at the same time.The main results show that:（1）The water consumption of alfalfa increased with the increase of irrigation amount,and the soil moisture of alfalfa field tended to decrease with the increase of water regulation.As the depth of soil deepened,it decreased first and then increased,and the soil moisture changes in different soil layers under light water regulation during the whole growth period was not significant.And the soil moisture could be kept within the normal growth range of alfalfa,which was beneficial to the growth of alfalfa and reduced the loss of water ineffective.Soil organic matter,alkali hydrolyzable nitrogen,available P and K decreased with soil depth,and pH had no significant difference.Water content regulation has significant influence on the content of pH,organic matter,alkali hydrolysable nitrogen,available P and K in 040cm soil layers.The content of organic matter and alkali hydrolysable nitrogen is increasing with the reduction of the degree of water regulation,and the content of pH,available P and K is decreasing.（2）The average plant height,stem diameter and hay yield in the growth period decreased with the increase of the cutting times,which showed the second cuttings than the third cuttings higher and increased with the decrease of water control degree.Water stress of different degrees in the branching period showed a certain compensation effect on plant height and stem growth after re-watering in the budding period.The yield of two stubble alfalfa hay was 4589.59 kg·hm-2 and3781.96 kg·hm-2 respectively under the treatment of mild water control at branching stage,and there was no significant difference from CK treatment（P>0.05）.The water control at the branching stage was more favorable to the growth and yield of alfalfa than in the budding stage.Light water regulation during the budding stage and the whole growth period will not cause a significant decrease in the alfalfa plant height.The WUE of hay yield decreased with the water control degree,and the maximum WUE of hay yield under the A9 treatment of the both stubble alfalfa was 3.47 kg·hm-2 and 2.96 kg·hm-2 respectively.（3）With the increase of the cutting times,the stem/leaf ratio was the second stubble more than the third stubble,the crude protein content was the second stubble less than the third stubble,the stem/leaf ratio and the crude protein content increased and then decreased with the reduction of water control degree.The reasonable water treatment in the branching stage was better than the budding stage in reducing the stem/leaf ratio and accumulation of crude protein content.The minimum of stem/leaf ratio of the both stubble alfalfa,under the light water regulation of the whole growth period,was 1.29 and 0.88 respectively,and the highest content of crude protein was21.08%and 23.26%respectively.The yield of crude protein was the same trend as the yield of hay.The yield of crude protein declined from the second cutting to the third cutting,and the yield of crude protein increased with the degree of water regulation to reduce.The highest yield of crude protein under the control of A3 treatment in the two cuttings alfalfa was 902.90 kg·hm-2 and825.26 kg·hm-2 respectively,but there was no significant difference from the light water regulation in the whole growth period,and light water regulation in the branching period and the whole growth period was more beneficial to the increase of crude protein yield.The WUE of quality decreased with the degree of water regulation to reduce,and water regulation in the branching period was more beneficial to improve the WUE of quality than the budding stage.The WUE obtained from the hay yield was basically the same.The reasonable water control during the whole growth period was beneficial to improve the quality of WUE.And the highest WUE of the second and third stubble alfalfa were 0.64 kg·m-3 and 0.55 kg·m-3 respectively under the treatment of severe water regulation and light water regulation during the whole growth period.（4）With the increase of the cutting times,the content of crude fat（CF）and crude ash（CA）increased,and the contents of acid detergent fiber（ADF）and neutral detergent fiber（NDF）decreased.With the reduction of the degree of water regulation,the content of crude fat and ash increased,and the content of ADF and NDF decreased first and then increased,and the relative feed value（RFV）increased first and then decreased.Water regulation in the budding stage was more beneficial to increase the content of CF and CA.Water control in branching period was more beneficial to reduce the content of ADF and NDF in alfalfa and increase the RFV value.The content of ADF and NDF was the lowest under the light water regulation treatment of the whole growth period（A7）,and the maximum RFV value was 169.32 and 223.48,respectively.（5）The grey correlation analysis method based on hay yield and quality of WUE,crude protein yield and RFV,etc.the effects of each index on the performance of alfalfa,in turn,were:protein yield,hay yield,protein water use efficiency,RFV and hay yield water use efficiency.The weighted correlation degree under A7 is 0.8052,followed by A2,A3,CK,A9,A8,A6,A1,A4,A5.The moisture control in the branching period was beneficial to the improvement of the performance of alfalfa,and the best comprehensive character under the light water regulation treatment of the whole growth period was the best suitable for the water control of the local alfalfa.It was beneficial to achieve high yield&quality in a ideal water saving model.