| The dryland farming area in northern China is the key development area for grain production in twenty-first century. The imbalance spatial and temporal distribution of rainfall and seasonal drought seriously restrict the increase of agricultural productivity in this area. Rainfall harvesting with ridge and furrow is a field rainfall harvesting technology, which can collect the rainfall from plastic-covered ridges serving as a rainfall harvesting zone to the furrows serving as a planting zone. This technology can effectively improve the supply of water for crops, promote the growth of crops, and increase the yield and efficiency of water use, which has become one of vital measures to improve the productivity of arid crops.Through the combined methods of the field point tests from2007to2010, DNDC modeling and GIS technology, this research studied on the differences of soil temperature and moisture and yield between rainfall harvesting with ridge and furrow and traditional flat planting in the arid farming area. DNDC modeling was improved, validated and sensitivity analysed with field observation data. With GIS technology, the spatial and temporal variations of soil moisture, yield of maize for both plastic-covered ridge-furrow for rainfall harvesting and traditional flat planting in the arid farming area in Shaanxi province from2001to2010were simulated, in order to determine the farmland water control effects and yield effects of the ridge-furrow planting for rainfall harvesting system on a regional scale.1. The soil temperature and moisture, yield and efficiency of water use of rainfall harvesting with ridge and furrow system1) The treatment of plastic-covered ridge and furrow planting for rainfall harvesting significantly increased the water storage of the soil from0to200cm. For3years of spring maize growth period, the mean of soil water storage treated with FM on the0-200cm soil was increased40.07mm, which was increased by10.56%, compared to the control. For3years of the whole growth period of winter wheat, compared to the control, the mean of soil water storage treated with FM on the0-200cm soil was increased17.17mm, which was increased by5.26%. The plastic-covered ridge and furrow planting mode for rainfall harvesting had more effect to the soil moisture conservation for0-100cm soil than for100-200cm soil. For3years of the whole growth period of spring maize,0-20cm soil retreated with FM and CK had the similar dynamic variations of soil moisture, compared the soil of20-60cm with the same treatments, which had jagged fluctuations with the variations of the amount of rainfall. However, the moisture of60-120cm and120-200cm soil was less affected by the amount of rainfall, which had flat fluctuations. For3years of growth period of winter wheat, the moisture of0-20cm soil and20-100cm soil retreated with FM and CK changed obviously with the variations of the amount of rainfall. However, the moisture of100-200cm soil water was not influenced much by the amount of rainfall, which had gentle changes.2) For spring maize,60days after sowing, compared with CK, the mean temperature of the0-20cm soil was dramatically increased by1.76℃when treated with FM, which had the best effect at2pm, with an increase of1.95℃. It was demonstrated that plastic-covered ridge and furrow planting for rainfall harvesting significantly increased the soil temperature during the earlier growth stage of maize. While the daily variation of soil temperature at different soil layers indicated that soil temperature in four soil layers (5cm,10cm,15cm,20cm) showed the same trend for FM treatment and CK, soil temperature increased with soil depth reduction. Out of them, the temperature of soil at5cm and10cm changed greatly, and the one at5cm was most sensitive. The temperature of soil at15cm and20cm had small changes.3) The plastic-covered ridge and furrow planting for rainfall harvesting significantly increased the yield of maize and winter wheat. Compared to CK, the mean yield,1000-grain weight, grain number per spike, spike length and efficiency of water use of the spring maize treated with FM were significantly increased by20.37%,8.82%,11.31%,8.48%, and23.48%, respectively. Due to the variations of the illumination and the amount of rainfall, there were variations in yield of spring maize among different years. The yield in2010was greater than the one in2008, which was greater than the one in2009. Compared to CK, the increased yield and efficiency of water use with FM treatment in2008were greats than those in2010, which were greater than those in2009. The yield,1000-grain weight, grain number per spike, spike number and water use efficiency of winter wheat treated with PF were increased than those of CK by19.85%,3.68%,5.70%,10.54%and19.81%, respectively. Compared the CK, the increased yield of winter wheat with FM treatment in2008-2009was greater than that in2009-2010, which was greater than that in2007-2008.2. Improvement, validation and sensitivity analysis of DNDC modeling1) In this research, the plastic-covered ridge and furrow planting for rainfall harvesting served as a measure of farmland management, which was combined with pedohydrology and biogeochemical process to calculate the temperature and moisture of soil in the new version DNDC modeling. Furthermore, duration of planting pattern and the rate plastic-covered ridge were used as two parameters, which made the DNDC modeling get the ability to simulate the moisture and temperature of soil and productivity effects with the plastic-covered ridge and furrow planting for rainfall harvesting system.2) DNDC modeling was corrected and validated with the observation data of soil temperature, soil moisture and crop yield under both plastic-covered ridge and furrow planting for rainfall harvesting (FM) and conventional flat planting (CK) conditions from2008to2010in Heyang, Shaanxi province. The results showed that new version DNDC modeling represented the dynamic variations of the temperature and moisture of soil and yield of spring maize under FM and CK treatments, and the simulated value and observation value were significantly correlated.3) The sensitivity analysis results showed that the effects of meteorological factors, such as the amount of rainfall and temperature, the soil texture and the amount of nitrogen fertilizer on crop yield were not the identical under FM and CK treatments. For CK, sensitivity of crop yield to the parameters from large to small was the amount of rainfall, the amount of nitrogen fertilizer, soil texture and temperature. However, for FM, sensitivity of crop yield to the parameters from large to small were the amount of nitrogen fertilizer, the amount of rainfall, soil texture and temperature, which demonstrated that FM treatment could relieve the effects of the amount of rainfall to crop yield. FM in the area lacking of rainfall is more effective to increase crop yield than in the area with enough rainfall.3. Modeling of soil moisture effects and maize yield with ridge and furrow planting for rainfall harvesting in Shaanxi province1) The mean amount of rainfall was609.2mm between2001and2010, which gradually increased from north to south in Shaanxi province. The southwest area of Shaanxi province had the most amount of rainfall, followed by Guanzhong area, and the north of Shaanxi province had the least amount of rainfall. The annual rainfall of12locations did not show any obvious increase or decrease trend from2001to2000. However, the locations with the amount of rainfall over700mm had great inter-annual fluctuation.2) The simulated results of maize farmland soil evaporation during10years showed that the spatial variation of plastic-covered ridge and furrow planting for rainfall harvesting was not consistent with that of flat planting. Compared to flat planting, the locations with over190mm of annual soil evaporation decreased from94districts to16districts with ridge-furrow planting for rainfall harvesting system, with the rest of the locations with that under190mm. The maize farmland soil evaporation of12locations with ridge and furrow planting for rainfall harvesting system were significantly lower than those with flat planting. The mean annual soil evaporation compared to flat planting decreased by67.62%.3) With the modes of plastic-covered ridge and furrow planting for rainfall harvesting and flat planting of maize, the average soil water storage in various regions10a of Shaanxi province showed a gradually increasing trend from north to south, which was the same as the trend of the average annual amount of rainfall. Compared to flat planting, the locations with less than85mm of annual soil water storage decreased from17districts to12districts with ridge and furrow planting for rainfall harvesting system. Out of them, the minimum annual soil water storage with flat planting and with ridge-furrow planting for rainfall harvesting system were59mm and79mm respectively. The locations with over145mm of the annual soil water storage with ridge and furrow planting for rainfall harvesting system increased from16to20. Except for Luonan, Zhen’an and Pingli with over700mm of the annual average rainfall, the annual soil water storage of the rest of9locations fluctuated seriously upon the amount of rainfall.4) The average moisture stress of10a represented a gradually decreasing trend from north to south, which was most serious in the area with annual rainfall below500mm. While in the locations with an average annual rainfall over700mm, there were no moisture stress during the growth of maize with the two kinds of planting modes, which was due to the moisture stress relieved by the increasing of rainfall. Compared to flat planting, with plastic-covered ridge and furrow planting for rainfall harvesting system, the average moisture stress of10a in6districts in north of Shaanxi and14districts in central of Shaanxi relieved, which gradually closed to1.5) The results of simulated yield demonstrated that:a. the average yield of maize in Shaanxi province with plastic-covered ridge and furrow planting for rainfall harvesting system and flat planting were13.2M tons and11.4M tons per annual, respectively. Compared to flat planting, with plastic-covered ridge and furrow planting for rainfall harvesting system, the average yield of10a in Shaanxi province increased1.8M tons, which increased by16%. b. The increased yield effect was most significant in the areas in north of Shaanxi, with the average annual rainfall less than500mm, and the yield increased2000to3500kg·hm-2. The effect during the year lack of rainfall was higher than the one with more rainfall, c. a trend of gradual decrease from north to south was represented, in contrast with the space distribution of the average annual rainfall. d. In south of Shaanxi areas with700to800mm of the average annual rainfall, the effect of increasing yield with ridge-furrow planting for rainfall harvesting system was lower, with the yield increased1to1000kg·hm-2. e, In south of Shaanxi areas with over800mm of the average annual rainfall, ridge and furrow planting for rainfall harvesting system had a negative effect on yield increasing. |
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