Effects Of Ridge-furrow Rainwater Harvesting With Maize Straw Biochar Application On Alfalfa Production

The purpose of this study is to determine a suitable maize straw biochar application rate and optimum ridge width for alfalfa production using ridge-furrow rainwater harvesting system with maize straw biochar application in the semi-arid regions of China.Ridges runoff observation experiment?1?and alfalfa production using ridge-furrow rainwater harvesting system experiment?2?were conducted in a randomized block design with 3 replications during 2017 alfalfa growing season.?1?There were 9 treatments?3 ridge widths×3 maize straw biochar application doses?in the runoff observation experiment with maize straw biochar application,which was conducted to investigate the runoff characteristics of ridges.The prediction of runoff was calculated using Soil Conservation Service Curve Number model and Modified Curve Number model.?2?there were 10 treatments?3 ridge widths×3maize straw biochar application doses+1 traditional flat planting as control?in the ridge-furrow rainwater harvesting system with maize straw biochar application for alfalfa production,which was conducted to investigate the effects of maize straw biochar application rate and ridge widths on soil moisture,soil temperature,soil nutrient,forage yield,water use efficiency?WUE?and nutritional quality of alfalfa.Alfalfa growth characteristics,forage yield,WUE and nutritional quality of alfalfa were evaluated using the Grey Incidence Degree Analysis.The main results are as follow:The mean annual runoff efficiency for MCS₃₀,MCS₄₅,MCS₆₀,SMB₃₀,SMB₄₅,SMB₆₀,DMB₃₀,DMB₄₅ and DMB₆₀0 were 15.48%,17.65%,19.84%,12.81%,14.51%,16.14%,10.67%,12.78%and 13.80%,respectively.MCS,SMB and DMB are abbreviated for ridges with manually compacted soil,single maize straw biochar application,and double maize straw biochar application,respectively,and the ridge widths of MCS₃₀,MCS₄₅5 and MCS₆₀(SMB₃₀,SMB₄₅ and SMB₆₀ or DMB₃₀,DMB₄₅5 and DMB₆₀)were 30,45,and 60 cm,respectively.The results revealed that mean annual runoff efficiency increased as ridge width and maize straw biochar application rate increased.The simulation accuracy of MoCN model was better than that of standard SCS-CN model.Compared with the standard SCS-CN model,the Nash-Sutcliffe coefficient and the correlation coefficient of the MoCN model increased by40.00%-275.00%and 1.31%-20.03%,respectively.The ridge-furrow rainwater harvesting with maize straw biochar application for alfalfa production obviously increased soil water content within roots zone,and alleviated drought stress.Soil water storage was in the order MCS>SMB>DMB>FP,and increased as ridge width increased.Compared to FP during the alfalfa growing seasons,the increase of soil water storage for MCS₃₀,MCS₄₅,MCS₆₀,SMB₃₀,SMB₄₅,SMB₆₀,DMB₃₀,DMB₄₅ and DMB₆₀0 were 27.30,46.41,60.08,20.10,35.17,48.80,15.65,15.45 and 38.95 mm,respectively.The difference of soil temperature at the furrow bottoms between different treatments was not obvious,but those at the ridge tops between different treatments was obvious.The soil temperature at the ridge tops increased as ridge width and maize straw biochar application rate increased.Compared to FP during the alfalfa growing seasons,the increase of topsoil effective accumulated temperature at the ridge tops for MCS₃₀,MCS₄₅,MCS₆₀,SMB₃₀,SMB₄₅,SMB₆₀,DMB₃₀,DMB₄₅ and DMB₆₀0 were 63.62,171.57,278.04,211.15,315.18,420.74,364.24,463.66 and 566.84°C,respectively.The ridge-furrow rainwater harvesting with maize straw biochar application for alfalfa production increased average soil nutrient content and pH in 0-60 cm depth at harvesting.The average soil nutrient content and pH increased as ridge width and maize straw biochar application rate increased.The average soil total nitrogen content and organic matter content were in the order DMB>SMB>MCS>FP,and the available phosphorus content,available potassium content and pH were in the order DMB>SMB>FP>MCS.Compared to FP,the average soil total nitrogen content increased by 2.07%,41.16%and 52.95%for MCS,SMB and DMB,respectively.For the same treatments,the average organic matter content increased by 7.49%,11.66%and 15.98%,respectively.The ridge-furrow rainwater harvesting with maize straw biochar application improved soil water content and soil effective accumulated temperature,leading to high plant growth and biomass formation.Compared to FP,annual total forage yields increased by 8.36%,39.72%,40.19%,31.44%,32.12%,31.77%and 11.08%for MCS₄₅,SMB₃₀,SMB₄₅,SMB₆₀,DMB₃₀,DMB₄₅5 and DMB₆₀,respectively,but annual total forage yields decreased by 5.13%and 0.01%for MCS₃₀ and MCS₆₀,respectively;WUE increased by 7.70,14.11,15.07,13.35,19.00,22.47,10.50,15.34 and 16.54 kg ha^-11 mm^-11 for MCS₃₀,MCS₄₅,MCS₆₀,SMB₃₀,SMB₄₅,SMB₆₀,DMB₃₀,DMB₄₅5 and DMB_60,respectively.The ridge-furrow rainwater harvesting with maize straw biochar application increased alfalfa crude protein content and phosphorus content,but decreased neutral detergent fiber content and acid detergent fiber content.The crude protein content and the phosphorus content increased as ridge width increased,while the neutral detergent fiber content and acid detergent fiber content decreased as ridge width increased.Compared to FP,the crude protein content increased by 8.84%,23.86%and 24.16%for MCS,SMB and DMB,respectively.For the same treatments,the phosphorus content increased by 5.98%,16.12%and 23.67%,respectively,whereas the neutral detergent fiber content decreased by 13.58%,8.80%and 4.90%,respectively,the acid detergent fiber content decreased by 14.17%,12.94%and 9.22%,respectively.Plant height,branches,forage yields,WUE and nutritional quality of alfalfa were evaluated by the Grey Incidence Degree Analysis,and the order of equiweight correlation degree and weighted correlation degree were SMB₆₀>DMB₆₀>SMB₄₅>MCS₆₀>DMB₄₅>SMB₃₀>DMB₃₀>MCS₄₅>MCS₃₀>FP.Based on the comprehensive analysis of the forage yields and quality of alfalfa,the optimum ridge width was 60 cm,and the suitable maize straw biochar application rate was 3×10⁴ kg ha^-1 in ridge-furrow rainwater harvesting for alfalfa production.