The Crop Growth Of Different Year In Alfalfa Rotation Field And The Soil Environmental Research

Alfalfa in the adjustment of the structure of agricultural production, improve theecological environment has significant economic, ecological and social benefits. In the LoessPlateau drought, due to drought, Long-term planting alfalfa cause drought, low nutrientcontent, low soil productivity caused by crop failures, seriously restricting the sustainabledevelopment of the regional economy. An alfalfa-crop rotation trial had been conducted toinvestigate the soil nutrients, soil moisture, crop yields and crop biological characteristicsafter plowing alfalfa grassland which of different three years, aiming to provide a theoreticalbasis to the Loess Plateau alfalfa grass sustainable development of farming systems. The mainconclusions are as follows:1. Alfalfa of different growth years had differences in restoring soil moisture, growth tofourth, six, eight and nine years of alfalfa in the0to500cm depth soil moisture are16.3%,15.4%,18.4%and20.6%, the trend of soil water content at first is decreasing and thenincreasing. The four years alfalfa’s soil drought layer is160cm, six years alfalfa’s soil droughtlayer is140cm, eight years alfalfa’s soil drought layer is300cm, nine years alfalfa’s soildrought layer is480cm. There are also differences in restoring soil moisture of differentalfalfa-crop rotation patterns. The alfalfa-leisure (AF) mode is the best one in three yearsexperiment, Which0~500cm layer soil moisture increased by10.66%,15.8%,12.7%thanbefore plowing alfalfa grassland，the alfalfa-winter wheat(AW) is the worst mode, the soilmoisture only increased by1.0%,1.8%,1.4%than before plowing alfalfa grassland，waterrestoration effect is not obvious. Indicated that the long-term cultivation of alfalfa can causesoil drought, and through the alfalfa grass-crop rotation can play the role of soil moisturerecovery.2. Alfalfa-crop rotation could increase soil available nitrogen, total nitrogen and organicmatter content than conventional farmland. After the four-year-alfalfa plowing, in the0-60cmlayer,the soil available nitrogen, soil total nitrogen and soil organic matter of the alfalfa-croprotation treatment respectively increased by16.5%~22.2%（P<0.05）,6.8%~13.9%（P<0.05）,8.9%~13.7%（P<0.05）than that of continuous rape planting, compared with continuous cropping of winter wheat, respectively increased by16.9%~22.6%（P<0.05）,7.0%~14.2%（P<0.05）,8.0%~12.7%（P<0.05）.After six-year-alfalfa plowing, the0-60cm layer soilavailable nitrogen, soil total nitrogen and soil organic matter of the alfalfa-crop rotationtreatment respectively increased by24.8%~39.8%（P<0.05），26.5%~35.3%（P<0.05）,9.0%~14.3%（P<0.05）than that fallow land, compared with continuous rapeplanting, respectively increased by30.8%~46.4%（P<0.05）,33.5%~42.8%（P<0.05）,10.2%~15.6%（P<0.05）, compared with continuous cropping of winter wheat,respectively increased by24.0%~38.8（P<0.05）,37.8%~47.4%（P<0.05）,9.5%~14.8%（P<0.05）.After eight-year-alfalfa plowing, the0-60cm layer soil available nitrogen, soiltotal nitrogen and soil organic matter of the alfalfa-crop rotation treatment respectivelyincreased by40.0%~52.8%（P<0.05）,21.0%~23.8%（P<0.05）,14.2%~19.4%（P<0.05）thanthat fallow land, compared with continuous rape planting, respectively increased by79.9%~96.3%（P<0.05）、14.9%~17.6%（P<0.05）、13.8%~19.0%（P<0.05）, compared withcontinuous cropping of winter wheat, respectively increased by57.2%~71.5%（P<0.05）、10.0%~12.6%（P<0.05）、7.2%~12.1%（P<0.05）, indicated that the alfalfa-crop rotation canenhance the soil fertility and increase soil available nitrogen, total nitrogen and organic mattercontent.3. The alfalfa-crop rotations in0-60cm layer soil available P, available K aresignificantly lower than fallow land and conventional farmland(Winter wheat and winteroilseed rape), but alfalfa-crop rotation could increase soil available P, available K content thanalfalfa grassland. After four-year-alfalfa plowing, the0-60cm layer soil average P of thealfalfa-crop rotation treatment respectively increased by14.2%~37.4%（P<0.05）than that ofcontinuous alfalfa grassland. After six-year-alfalfa plowing, the0-60cm layer soil average P,available K of the alfalfa-crop rotation treatment respectively increased by19.3%~25.2%（P<0.05）,5.8%~13.4%than that of continuous alfalfa grassland. After eight-year-alfalfaplowing, the0-60cm layer soil average P, available K of the alfalfa-crop rotation treatmentrespectively increased by290%~37.7%（P<0.05）,7.5%~12.4%（P<0.05）than that ofcontinuous alfalfa grassland. Indicated that the alfalfa-crop rotation can alleviate the status offertility over consumption of alfalfa grass, and enhanced the soil fertility. Indicated that thelong-term cultivation of alfalfa can cause soil available P, available K decreased, and throughthe alfalfa grass-crop rotation can play the role of enhancing soil fertility.4. Alfalfa-crop rotation could increase soil available ammonia nitrogen, nitrate contentthan conventional farmland. After six-year-alfalfa plowing, the0-100cm layer soil averageavailable ammonia nitrogen, soil average nitrate of the alfalfa-crop rotation treatmentrespectively increased by46.8%~418.0%（P<0.05）,8.5%~62.2%（P<0.05）than that fallow land, compared with continuous rape planting, respectively increased by100.1%~606.3%（P<0.05）,2019.0%~79.3%（P<0.05）, compared with continuous cropping of winter wheat,respectively increased by1212.0%~683.5%（P<0.05）,30.5%~95.0%（P<0.05）, comparedwith continuous Alfalfa grassland, respectively increased by72.6%~419.7%（P<0.05）、33.8%~65.1%（P<0.05）. Indicatted that the alfalfa-crop rotation can promote the formation ofsoil mineralized nitrogen.5. Alfalfa-crop rotation could significantly increase yields. Three years experiments allshowed that the crop yields of winter wheat and rotating rape are higher than the conventionalfarmland. From2007to2008, the rape yield of rotation cropping cropland increased by91.1%than that of continuous rape farmland, the wheat yield increased by25.0%thancontinuous wheat farmland. From2009to2010, the rape yield of rotation cropping croplandincreased by28.9%than that of continuous rape farmland, the wheat yield increased by43.2%than continuous wheat farmland. From2011to2012, the rape yield of rotationcropping cropland increased by72.5%than that of continuous rape farmland, the wheat yieldincreased by47.3%than conventional wheat farmland.6. Alfalfa-crop rotation could promote dry matter accumulation effectthe and plantheight, significantly higher than conventional farmland.