【作者】 刘沛松；

【导师】 贾志宽；

【作者基本信息】 西北农林科技大学 ， 生态学， 2008， 博士

【摘要】 本文以宁南旱区人工苜蓿草地为研究对象,在2004～2005年连续两年中,对不同生长年限紫花苜蓿草地0～700cm和0～1000cm深层土壤水分状况进行了测定;于2003～2005年期间,对10年生紫花苜蓿与春小麦、谷子和马铃薯进行了为期3年的田间定位草田轮作试验,分析比较了不同轮作方式的作物水肥利用特征、总产量、水分利用效率、降水生产效率、氮素利用效率以及不同草田轮作方式完成后的茬口养分和土壤酶活性差异。研究结论对宁南旱区草地管理及草田轮作具有重要的理论及实践意义,主要研究结果如下:1.通过连续两年对宁南山区不同生长年限的苜蓿土壤深层水分进行测定,结果表明:（1）随着苜蓿生长年限的增加,土壤整体上干燥化程度加剧。2004年测定的4、7和12年生苜蓿地0⁷00cm土层平均含水率分别为5.30%、5.22%和5.01%,2005年测定的3、6和10年生苜蓿地0⁸00cm平均含水率分别为6.26%、5.60%和5.27%。3年生以后,苜蓿根系已达300cm以下,对300cm⁸00cm土层水分消耗强烈,而对300cm以上土层水分消耗减缓。（2）根据不同生长年限苜蓿土壤深层水分分布和动态分析,可将土壤剖面分为四个层次:降水蒸发易变层（0¹00cm）、降水继续扩散层（100³00cm）、根系耗水干燥层（300⁸00cm）和深层储水调节层（800cm¹000cm以下）。（3）苜蓿在6年生前,耗水深度和干层厚度逐年迅速增加;6年生时耗水深度和干层厚度均超过1000cm,0¹000cm平均含水率仅5.73%,土壤水分亏缺严重;7¹2年生苜蓿生长衰退,耗水深度和干层厚度有所减小,300⁷00cm干层湿度仅维持在4.0%左右水平,而800¹000cm水分有回升现象。2.草田轮作对恢复退化苜蓿草地土壤干层水分有可行性。以各类作物农田水分为对照,连续两年对宁南山区不同生长年限紫花苜蓿深层土壤水分以及10年生紫花苜蓿地耕翻后轮作不同年份作物农田的水分进行了测定,结果表明,随着苜蓿生长年限的增加,干层深度与厚度先增加后减小。3年生苜蓿干层深度为720cm,6年生干层最深可达1000cm以下,10年生干层深度为920cm,3¹2年生苜蓿地0⁷00cm土层基本上均属于土壤干层范围。苜蓿地0⁸00cm土壤湿度随生长年限增加而降低,2004年测定的4、7和12年生苜蓿地0⁷00cm土层平均含水率分别为5.30%、5.22%和5.01%;2005年测定的3、6和10年生苜蓿地0⁸00cm土层湿度分别为6.26%、5.60%和5.27%;而800¹000cm土层湿度在一定年限后有恢复趋势。300cm为苜蓿地降水下渗的最大临界深度,300cm以下土壤干层一旦形成,将长期存在,7¹2年生苜蓿300⁷00cm土层湿度仅维持在4.0%左右。苜蓿地和农田的土壤干层厚度与湿度有较大差异,草田轮作可使苜蓿土壤干层水分基本恢复到农田湿度,而且轮作年份越长,土壤各层次水分恢复效果越好,10年生苜蓿轮作18年后土壤水分基本恢复到农田状态。3. 2002²004年对宁南旱区不同生长年限紫花苜蓿土壤理化性状和紫花苜蓿-谷子轮作进行了试验研究,结果表明,随着紫花苜蓿生长年限延长,土壤生态环境得到改善。紫花苜蓿3²2年生期间,0¹00cm土壤容重减小了0.213 g/cm3,孔隙度增加8.03%,饱和持水率增加14.17%,持水能力增强。6²2年生期间,0⁶0cm土层有机质和氮素平均含量分别增加1.60 g/kg和11.02 mg/kg,pH值降低了0.09,为轮作作物生长创造了良好的土壤环境。紫花苜蓿轮作年份越早,土壤水分恢复效果越好,轮作作物水分利用效率（WUE）越高;反之,紫花苜蓿生长时间过长,轮作后不利于土壤水分的恢复。6、10和22年生紫花苜蓿地轮作谷子收获后,0²00cm土壤水分恢复量分别为63.06 mm、55.22 mm和-42.55mm,轮作谷子产量分别为1725.95 kg/hm2、1485.80 kg/hm2和1560.75 kg/hm2,水分利用效率分别为12.0116 kg/mm.hm2、8.4325 kg/mm.hm2和5.8161 kg/mm.hm2,紫花苜蓿实行草田轮作的最适宜年限为5⁶年生。4. 2003年²005年在黄土高原宁南旱区10年生退化苜蓿草地上进行了连续3年不同作物组合方式的轮作试验。结果表明,轮作地0⁶0cm土层易受降水和地面蒸发影响,轮作作物对土壤水分消耗主要集中在0～120cm土层;在120 cm 200cm土层范围内,随着轮作年限的增加,土壤水分表现出不断恢复趋势。5.经过在10年生退化苜蓿草地进行了连续3年的27种草田轮作方式的试验表明,轮作第一年对苜蓿土壤水分的恢复是主要的。轮作作物种类和组合方式不同,对土壤水分消耗的强度及深度不同,导致土壤含水量出现较大差异。在草田轮作的3种轮作作物中,无论在何种降水年型下,马铃薯都表现出较高的产量、水分利用效率和降水生产效率,达到对有限降水资源的充分利用,适应宁南山区的气候条件,是草田轮作的首选作物。春小麦收获后休闲期有利于雨季降水在土壤的下渗,保持了农地水分的平衡。所以,苜蓿翻耕后轮作第一年以种植马铃薯为宜,当土壤水分过耗时种植春小麦可利用收获后的休闲期集纳雨季降水,以促进农田水分平衡。6.苜蓿草地耕翻轮作后,土壤有机质含量不断下降,尤其高产作物连作导致有机质含量下降幅度最大;氮素受作物产量和土壤水分的影响变幅较大;轮作可提高磷的有效性,土壤水分也影响作物对磷素的吸收,马铃薯对磷素需求量较大;轮作后pH值先升高后降低,低于苜蓿草地,因此草田轮作可降低土壤盐碱化程度。7.不同轮作方式下的第三年春小麦产量及土壤养分、pH值、酶活性各指标间差异性达到显著水平。0⁶0cm土层有机质、全氮、碱解氮和速效钾平均含量均下降,降幅分别为0.05².24 g/kg、0.019⁰.325 g/kg、0.118¹2.280mg/kg和8.87¹66.88 mg/kg,pH值下降0.03⁰.31。前一、二年轮作作物对水肥料的消耗有叠加效应,且随耕作年限递减。轮作第一年作物对养分的消耗是主要的,而且作物种类不同,消耗量不同。第一年为春小麦的轮作方式对土壤氮素和磷素消耗最少,为谷子时次之,为马铃薯时最多。谷子是喜钾作物,前茬有谷子参与时对土壤速效钾消耗最多,有马铃薯时次之,有春小麦时最少。轮作方式中马铃薯和谷子产量高,耗水量大,导致土壤pH值保持较高水平。作物连作导致土壤脲酶活性降幅较大,马铃薯连作使碱性磷酸酶活性降低,禾本科作物连作的土壤蔗糖酶活性较高。8. 10年生苜蓿草地翻耕后轮作的马铃薯-马铃薯-春小麦（PPW）方式为最佳的轮作模式,能够充分利用有限的降水资源。轮作结束后,土壤水分恢复效果较好,0²00cm土壤含水量、作物总产量、水分利用效率、降水生产效率和氮素利用效率均较高,分别为254.58mm、5214.5 kg/hm²、9.3786 kg/hm²·mm^-1、6.8711 kg/hm²·mm^-1和19.612 kg/kg.hm^-2,与其它轮作模式间差异达显著或极显著水平。更多还原

【Abstract】 This paper takes artificial alfalfa grassland in The arid area of southern Ningxia as object of study. During 2004~2005 year, the soil moisture status of different year old alfalfas grasslands are mensurated in soil layer with 0~700 cm and 0~1000 cm . And during 2003 to 2005, with the 10-year-old alfalfa grassland as previous stubble and take spring wheat, millet and potato as rotation grains, a three-year alfalfa-grain rotation orientation experiment has been carried out in HaiYuan, south Ningxia. The differences of 27 kinds of rotation patterns have been analyzed and compared in crops water and nutrition use characteristic, crops total yield, water use efficiency(WUE), precipitation productive efficiency, nitrogen use efficiency(NUE), and soil nutrition and enzyme activety in the crop rotation end. Research conclusion has important theory and practice significance for grassland management and alfalfa-grain rotation in arid area of southern Ningxia .The main results of the study are as followings:1. Deep soil profile moisture of different growth age alfalfa fields has been measured during successive 2 years (2004 and 2005 years) in southern Ningxia dry area. Results indicate: With the increasing of alfalfa’s growth age, soil desiccation degrees intensify in whole. Average contain moisture rates in 0~700cm soil layer of 4,7,12 growth age alfalfa fields, which has measured in 2004, is in turn 5.30%、5.22% and 5.01%; And those in 0~800cm depth of 3,6,10 growth age alfalfa fields, which has measured in 2005, is in turn 6.26%、5.60% and 5.27%. After 3 growth year, alfalfa taproot has reached under 300cm depth. So soil moisture of 300~800cm depth be consumed in intensity and 0~300cm soil moisture increase than before. According to moisture distribution and dynamic characteristics analysis on deeper soil profile of different growth age alfalfa fields, the soil profile be divided into four layers: Soil layer that moisture easy to change by precipitation and evaporation(0~100cm), Soil layer of precipitation continue to seep (100 to 300cm),Dry soil layer that water exhausted by alfalfa root system (300cm to 800cm) and layer regulated by water under deep soil that stored up(800~below 1000cm). Before 6 growth age, alfalfa’s soil moisture consumption depth and thickness are increasing by each year quickly. And in 6 growth age, both exceed 1000cm depth, and contain water in soil severely decrease, which 0~1000cm soil layer average moisture is only 5.73%. Alfalfa growth decline during its 7~12 growth age, soil moisture’s consumption depth and thickness are decreasing slightly, which contain moisture of 300~700cm dry soil layer only maintain 4% level, and those of 800~1000cm depth layer soil moisture has increase .2. Alfalfa-grain rotation has the feasibility in restores soil moisture of the degenerated alfalfa’s dry layer soil. In two consecutive years, the study measured the soil moisture content of farmland on which alfalfa had grown for different periods and the soil water content of farmland on which alfalfa had grown for ten years and then rotated with other crops in different years and then compared with the soil water content of those in different croplands. The study indicated that while alfalfa growth was prolonged the depth and thickness of the soil dry layer first increased and then declined. The depth of soil dry layer was 720 cm in the farmland with alfalfa growing for three years, at most 1000 cm in the farmland with alfalfa growing for six years , and 920 cm in the farmland with alfalfa growing for ten years and soil dry layer spanned from zero to nearly 700 cm soil in the farmlands with alfalfa growing for 3~12 years. In alfalfa farmlands, the average moisture content declined in 0~800 cm soil as the growth of alfalfa was prolonged. In 2004, the average soil moisture content was measured to be 5.30%, 5.22% and 5.01% in 0~700 cm soil in the farmlands with alfalfa growing for 4, 7 and 12 years respectively. In 2005, the soil moisture was measured to be 6.26%,5.60% and 5.27% in 0-800 cm soil in farmlands with alfalfa growing for 3, 6 and 10 years respectively. But the soil moisture tended to rebound in 800~1000 cm after alfalfa grew for a certain period. A soil depth of 300 cm is the maximum depth to which the rainwater could infiltrate. Thus the soil dry layer, tended to stay permanently once it formed in soil below 300 cm deep. The soil moisture remained only 4.0% in 300~700 cm soil in the farmlands with alfalfa growing for 7~12 years. The thickness and moisture content of the soil dry layer differed greatly between alfalfa farmland and cropland, but alfalfa-crop rotation made the soil moisture of the soil dry layer recover substantially worse than those of the croplands and this effect was intensified in different soil layers as the rotation was prolonged. Furthermore, the 18-year alfalfa-crop rotation made the farmland with alfalfa growing for 18 years recover its soil moisture content to a level similar to that of cropland.3. It is studied that soil physical and chemical properties of different year old alfalfas and alfalfa-millet crop rotation in Arid Region of Southern Ningxia during from 2002 to 2004 year. The results indicated that with the increasing of alfalfa growth year, soil ecological environment be improved. Alfalfa was growing during from 3 to 22 years old, soil bulk density reduced 0.213 g/cm3, soil porosity added 8.03%, and soil hold water saturation ratio increased 14.17%, so soil hold capacity was strengthened. During from 6 to 22 years old of alfalfa, soil organic matte and nitrogen content in 0~60cm depth increased 1.60 g/kg and 11.02 mg/kg respectively. And pH value felt for 0.09, which supply better soil growing environment for rotation crops. The more ahead that alfalfa rotation year is, the better effect of soil moisture restoration is and the higher Water Use Effect of rotation crop is. When millets be harvested in farmlands after 6,10 and 22 years old alfalfa, which soil water restoration content in 0~200cm depth were 63.06 mm、55.22 mm and -42.55 mm, respectively. Millet yields that alfalfa-grain crop rotation , after 6,10 and 22 years old alfalfa ,were 1725.95 kg/hm2、1485.80 kg/hm2 and 1560.75 kg/hm2, and their WUE were 12.0116kg/mm.hm2、8.4325kg/mm.hm2 and 5.8161kg/mm.hm2, respectively. The alfalfa optimum growth year in grass-grain rotation is 5~6 year old.4. Experiment has been carried out that three kinds of crops including spring wheat, potato and millet are rotated on the 10-year-old degenerate alfalfa grassland in the drought areas of southern Ningxia on the loess plateau during 2003~2005. Results indicate, in alfalfa-crop rotation farmland, 0~60cm soil layer is apt to be influenced by precipitation and ground evaporation, the rotation crop mainly consumes water in 0-120cm soil layer; Within the range of 120 cm - 200cm soil layer, with the increasing of rotation year, the soil moisture show that trend is resuming constantly.5. The rotation experiments on the 10-year-old degenerated alfalfa grassland, which carried out for 3 years and included 27 kinds of alfalfa-crop rotation patterns, indicate that is mainly the first year rotation that crops restore the alfalfa soil moisture. The rotation grains’type and combination method are different, so causes that the soil moisture consumption’s intensity and the depth are different, and causes the soil moisture content to have the big difference. Regardless of under what kind of precipitation year, potato has much higher yields, water use efficiency and precipitation production efficiency than other two rotation crops, which make full of the limited precipitation resources and adapt climatic conditions of south Ningxia, so is first choice crop of alfalfa-grain rotation. After spring wheat harvest, the fallow period was advantageous in the rainy season precipitation infiltrates in soil, maintained farmland moisture content balanced. It suggest that, after alfalfa ploughing, the crop rotation first year should plant potato, and when soil moisture consuming too much, should rotate spring wheat to save water in growing period and convergence rainwaterl down the depth soil layer during the fallow period, and promotes the farmland water balance.6. After the alfalfa grassland be plowed and rotated by the crops, the soil organic matter content drops unceasingly, especially the high-yield crops plant in succession causes to drop much quickly; The nitrogen is greatly influenced by the crop output and soil moisture. The crop rotation may enhance the phosphorus validity. The soil moisture also affects the crops absorption for the phosphorus element. The potato demand the phosphorus element is much. After the crop rotation, the pH value begin to increase and then decrease, ultimately is lower than those of the original alfalfa grassland, therefore,the alfalfa-crop rotation may reduce the salting of soil degree.7. There are significant differences at above indexes of the third year rotation spring wheat of 9 kinds of alfalfa-grain rotation patterns. Organic matter、Tot. N、Alk.-hydr.N、Avai.K average contents and pH values of 0~60cm soil layers all decreased, which breadths is 0.05~2.24 g/kg、0.019~0.325 g/kg、0.118~12.280mg/kg、8.87~166.88 mg/kg and 0.03~0.31, respectively. It has cumulation effect that No.1 and No.2 year rotation grains absorb soil water and nutrients,which decrease by rotation year adds. It is dominating that rotation crops consume soil nutrient at the first rotation year and consumption quantity was different with crop species. When the first rotation crop is spring wheat, consumption of this rotation pattern’s soil N and P is the least of all, it is second when it is millet, and it is the most when it is potato. As millet favor to Avai.K, soil Avai.K was use greatly when former stubble grains was millet, it is more little than millet when former stubble grains was potato, and it is the least when spring wheat. Soil organic matter and Avai.P decrease greatly when those three grains rotate with free arrange in groups. In all rotation patterns, potato and millet use greatly soil water than spring wheat, so it leads to soil keep high pH value. In the alfalfa-grain rotation patterns, grain succession pattern induce to soil urease activity decline, which breath is much more than others. Potato succession pattern lead to soil Alkaline Phosphatase activity fall, soil invertase activity of crop succession pattern is more high than others.8.“10 years old alfalfa-Potato- Potato-Spring wheat”is optimal rotation pattern that soil restoring-water effects is better than other patterns and take full advantage of limit rainwater resources. Its 0~200 cm depth soil moisture, crops’total yields, WUE,Precipitation Productive Efficiency and NUE are higher than others, which are in turn 254.58mm、5214.5 kg/hm2、9.3786 kg/hm2·mm-1、6.8711kg/hm2·mm-1and 19.612kg/kg.hm-2. and has significantly differences(P< 0.05 or P< 0.01)between those of other patterns respectively.更多还原