The Productivity, Nureient Characteristics Of Artificial Alfalfa In Gully Region Of The Loess Plateau

By adopting the cooperation of field and indoor experiment method. Thephysical-chemical properties of soil and the production of Alfalfa (Medicago sativa) wasstudied by different method. Combined with2006,2008,2010and2012, the semi-humidregion of the Loess Plateau planting Alfalfa was studied. Also, continuous cropping aboutAlfalfa in2012by different fertilization and crop rotation by different growth duration wasstudied. The results are as follows:1. In semi-humid region of the Loess Plateau area, Alfalfa is suitable for planting for9years and the highest yield is the6th year, up to12609kg/hm~2. When it comes to18years later,the degeneration of Alfalfa comes up. After30years, Alfalfa growth is serious decline, andAlfalfa begins the transition to grass. The32years alfalfa ground’s output is only1717kg/hm~2. In the same year, the alfalfa yield is greatly different, which has a close relationshipwith the rainfall. If the rainfall is rich during the growth period, the yield of alfalfa is higherthan others.2. After years of continuous cropping on alfalfa ground, the soil moisture of soil layerincreases first, and then decrease with the growth period between0cm and200cm of the soil.The6years alfalfa is the highest, and then decrease. When it comes to32years alfalfa, thesoil moisture of soil layer is the lowest. Alfalfa growth under9years (including9years) canmake full use of limited precipitation. After9years, the efficiency of water use begins toreduce. When continuous cropping on alfalfa ground for32years, the efficiency of water useis only5.86kg/(mm·hm~2).3. The soil organic matter content, total nitrogen content, and alkali-hydrolysablenitrogen content of Alfalfa change the same with the planting years on. The content is thehighest in the7the year, and then it begins to reduce after the8th year. It is not until32yearslater, the soil nutrient begins to recover gradually. The soil total phosphorus content, availablephosphorus, and available potassium content of Alfalfa also change the same with the plantingyears on, which shows a trend of decline along with the years. The absorbing capacity of soilnitrogen, phosphorus, and potassium of Alfalfa changes the same. The absorbing capacity isthe highest in the6th year, and then it begins to reduce after the7th year. When it comes to32years later, the absorbing capacity is the lowest. 4. The yield of crop rotation alfalfa increases with the planting years on, then it begins toreduce in the3rd year, in which the yield of crop rotation alfalfa is10690kg/hm~2.5. The water consumption of crop rotation alfalfa is not a big difference, around630mm.In the first3years, it shows a increasing tendency, and then it begins to decrease after3years.Always, the water use efficiency is higher than10kg/(mm·hm~2), which indicates the croprotation alfalfa can make full use of the limited precipitation in Chang Wu Town (A town inXian Yang city, Shaanxi Province, China).6. The soil organic matter content, total nitrogen content, and alkali-hydrolysablenitrogen content of crop rotation Alfalfa shows an increasing tendency with the planting yearson. The soil phosphorus content and potassium content of Alfalfa decreases with the plantingyears on. At the same time, the absorbing capacity of nitrogen increases year by year. Theabsorbing capacity of1year’s alfalfa is10kg/hm~2, which is the lowest. The phosphorusabsorbing capacity of2years and3years’ alfalfa increases by60%and120%compared withthe1year alfalfa. The4years’ alfalfa decreases by23%compared with the3years’ alfalfa. Itis not until the3rd year, the potassium absorbing capacity of alfalfa begins to decrease, rangeof96-172kg/hm~2.7. The production of fertilizing continuous cropping alfalfa for29years differs. Thefertilizer area yield is higher. The yield of the NPM alfalfa area is the highest, and the averageof two years’ yield is11473kg/hm~2, which is2times than the no fertilizer area. Since, thealfalfa absorbs the soil nutrient is a long term, the production of the no fertilizer area is thelowest.8. By fertilizing the continuous cropping alfalfa in different ways, it indicates that thewater use efficiency of the fertilizer alfalfa area is higher than the no fertilizer area, and thetotal water consumption difference is not big, around640mm.9. The soil nutrient of fertilizer area is higher than the processing control area that is nofertilizer area by fertilizing continuous cropping alfalfa. The soil nitrogen content, organicmatter content and phosphorus content is more than10%,16%and24%, but the availablepotassium content is less than43%by NPM fertilizer treated compared with the area onlyfertilized phosphorus. The absorbing capacity of nitrogen, phosphorus and potassium ofalfalfa in fertilizer area is higher than the processing control area that is no fertilizer alfalfaarea, which indicates the NPM fertilizer treated alfalfa’s absorbing capacity of soil nutrient ishigher than the alfalfa which is only fertilized phosphorus.