The Effect And Soil Mechanism Of Improving Wheat Yield And Nutrients Content With Legume-winter Wheat Rotations

Frigile ecological environment, low fertility, and water scarcity during growing seasonare main factors limiting agricultural production in Northwesten China. Low soil nutrientsavailability further hampers dryland crop yields and quality, which are threatening local staplefood supply. Green manure as organic fertilizer, after being incorporated into soil can releasenitrogen, phosphorous, potassium, calcium, magnesium, varieous micronutrients and theorganic acids secreted by green manure roots disovling micronutrients bound with soilparticles. Green manure play a positive role in improving the crop nutrients content. Athree-year field experiment with four different agricultural management rigime: fallow-winter wheat cropping as control, soybean-winter wheat rotation, mungbean-winter wheatrotation and Localbean-winter wheat rotation was conducted to study the effects of differentlegume green manure-winter wheat rotations on wheat grain yield and nutritional quality, drymatter and nutrients translocation, and soil fertility. The aim of this study was to explicit theinfluence of green manure on agriculture production, and provide a sound basis for drylandfarming. The following results were obtained:1. Wheat grain yield and biomass decreased under three green manure-winter wheatrotations treatments in the first year,. The scond year2009-2010, Local bean-winter wheattreatment increased the grain yield by7.3%. And the third year, mungbean-winter wheattreatment increased grain yield and biomass by23.5%and21.6%, respectively, Localbean-winter wheat treatment increased yield and biomass by24.9%and23.7%, respectively,and soybean-winter wheat treatment had no significant effect on wheat yield or biomass. Infirst two years, compared with the fallow-winter wheat treatment,, wheat grain N contentincreased by6.4%and12.1%under the Local bean-winter wheat treatment; P contentincreased by22.2%and27.8%under mungbean-winter wheat treatment, and18.5%and27.8%under the Local bean-winter wheat treatment,11.1%and22.2%under thesoybean-winter wheat treatment. K content increased by8.8%under the mungbean-winterwheat treatment,11.8%under the local bean-winter wheat treatment,5.9%under thesoybean-winter wheat treatment in2008-2009. However green manure-wheat treatments hadno significant effect on K content in2009-2010. Zn content under the mungbean-winter wheat rotation was32.1%and29.0%higher than that of the control in2008-2009and2009-2010,while Local bean-winter wheat rotation increased Zn content by16.1%and9.3%andsoybean-winter wheat rotation.26.4%and27.4%. In the third year2010-2011, greenmanure-wheat rotation had no marked effect on grain N, P and K content, but decreased theCu and Zn content. Compared to the control, Cu content was reduced by8.6%,2.8%and8.6%under the mungbean-winter wheat treatment, Local bean-winter wheat treantment andsoybean-winter wheat treatment, respectively; and Zn content reduced by6.0%,13.3%and5.4%, respectively.2. The Local bean-winter wheat treatment increased the wheat dry weight by35.1%compared to the fallow-whinter wheat, the nitrogen accumulation increased by128.8%, andthe phosphorous accumulation increased by140%. In contrast, the soybean-winter wheattreatment reduced the wheat dry weight by26.7%and the nitrogen accumulation by44.2%.The mung bean-winter wheat treatment reduced the wheat dry weight by17.0%and thenitrogen accumulation by24.4%. The phosphorus accumulation of wheat was notsignificantly affected by either soybean-winter wheat treatment or mung bean-wintertreatment. Different from N and P, the potassium accumulation of wheat were all decreasedwith three legume green manure incorporated into soil. The decline in the potassiumaccumulation varied among the rotations. The post-anthesis potassium accumulation in theLocal bean-winter wheat treatment was3.8kg/hm2less than that of the control treatment. Incomparison, the potassium accumulation in the soybean-winter wheat treatment was12.6kg/hm2less than that of the control. The potassium accumulation in the mung bean-winterwheat treatments was5.5kg/hm2less than that in the control. The ratio of grain potassium totranslocated potassium under the Local bean-winter wheat treatment was81.0%. This amountwas higher than that of the control.While the ratio of grain potassium to translocatedpotassium was52.9%under the soybean-winter wheat treatment and66.8%under the mungbean-winter wheat treatments.3. Local bean-winter wheat treatment significantly increased the nitrate content duringthe period of anthesis, compared with the control, the nitrate content was increased by112.6%and77.6%in10-20cm and20-30cm soil layer. In0-10cm soil layer, available phosphorouscontent was24mg/kg higher under the mungbean-winter wheat treatment, and16mg/kghigher under the local bean-winter wheat treatment than that of control. During elongationstage, anthesis and filling stage, available phosphorous content was increased by an averageof5mg/kg in20-40soil layer with the soybean-winter wheat rotation. The effect on availablepotassium varied among different green manure rotations: Local bean-winter wheat treatmentreduced the soil available potassium content, however, mungbean-winter wheat treatment increased the available potassium content by7.1%and6.4%at elongation stage and fillingstage, respectively; soybean-winter wheat treatment increased the available potassium contentby4.0%and12.8%at elongation stage and filling stage, respectively. In10-40cm soil layer,green manure rotations increased DTPA-Mn by0.4-0.8mg/kg compared to the control duringthe elongation stage, and increased by0.05-0.09mg/kg in20-40cm soil layer at elongationstage, but had no significant effect on and DTPA-Cu.4. In0-10cm soil layer, soil nitrate and available phosphorous content decreased with thedistance from main stem. The difference between maximum and minimum nitrate content,was15.1mg/kg under the soybean-winter wheat treatment,11.2mg/kg under the Localbean-winter wheat treatment, and7.4mg/kg under the mungbean-winter wheat treatment. Asfar as0-10cm soil nitrate content of the control, the difference was the highest,15.9mg/kg.While the difference between maximum and minimum available phosphorous content was40mg/kg under the Local bean-winter wheat treatment,36mg/kg under the mungbean-winterwheat treatment and28mg/kg under the soybean-winter wheat treatment, while for the control,there was no significant difference with distance from the main stem, the P content wasbetween24mg/kg and26mg/kg, which was much lower than any of the three green manurerotation treatments. Soil DTPA-Mn content varied among treatments, DTPA-Mn content inthe0-10cm soil layer had a similar decreasing trend with the distance from the main stemunder the Local bean-winter wheat treatment and fallow-winter wheat treatments, and thelowest P content appeared at the points of9cm from the main stem. However, opposit fromthe control, DTPA-Mn in the0-10cm soil layer showed a increasing trend with the distancefrom the main stem. The far end from the main stem was higher than the proximal end tomain stem under the mungbean-winter wheat treatment, and there is no significant differencewith the distance from main stem under the soybean-winter wheat treatment. As the distance,available potassium, DTPA-Fe, DTPA-Cu and DTPA-Zn had no significant change among thetreatments.