Effects Of Ridge-furrow Rainwater Harvesting With Biochar Application On Sainfoin Production

The purpose of this study is to determine a suitable biochar type and optimum ridge width for sainfoin production using ridge-furrow rainwater harvesting system with biochar application in the semi-arid regions of China.Ridges runoff observation experiment?1?and sainfoin production using ridge-furrow rainwater harvesting system were conducted in a randomized complete block design with 3 replications during 2017 sainfoin growing season.?1?There were 9 treatments?3 ridge widths×3 biochar types?in the runoff observation experiment with biochar application,which was conducted to investigate the monthly runoff efficiency and the threshold rainfall to produce runoff of ridges;?2?there were 10 treatments?3 ridge widths×3 mulching materials+1 flat planting as cotrol?in the ridge-furrow rainwater harvesting system with biochar application for sainfoin production,which was conducted to investigate the effects of biochar types and ridge widths on soil moisture,soil temperature,soil nutrient,forage yield,water use efficiency?WUE?and nutritional quality of sainfoin.The main results are as follow:The predicted runoff efficiencies for MCS₃₀,MCS₄₅,MCS₆₀,MSB₃₀,MSB₄₅,MSB₆₀,CDB₃₀,CDB₄₅5 and CDB₆₀0 were 27.3%,29.8%,32.1%,22.6%,27.7%,28.4%,22.0%,26.1%and 27.3%,respectively.MCS,MSB and CDB are abbreviated for ridges with manually compacted soil,maize straw biochar application,and cow dung biochar application,respectively,and the ridge widths of MCS₃₀,MCS₄₅5 and MCS₆₀(MSB₃₀,MSB₄₅ and MSB₆₀ or CDB₃₀,CDB₄₅5 and CDB₆₀)were 30,45,and 60 cm,respectively.The threshold rainfall to produce runoff of ridges were 4.4,4.2,3.9,4.3,5.0,4.6,5.0,5.3 and 4.9 mm for the respective treatments.The mean predicted runoff efficiencies for MCS,MSB and CDB were 29.7%,26.2%and 25.1%,respectively,while the threshold rainfall to produce runoff for the respective treatments were 4.2,4.6 and 5.1 mm.The results revealed that runoff efficiency increased as ridge width increased.The ridge-furrow rainwater harvesting with biochar application increased soil water content within roots zone.Soil water storage was in the order MCS>MSB>CDB>FP,and increased as ridge width increased.Compared to FP during the sainfoin growing seasons,the increase of soil water storage for MCS₃₀,MCS₄₅,MCS₆₀,MSB₃₀,MSB₄₅,MSB₆₀,CDB₃₀,CDB₄₅ and CDB₆₀ was 17.4,24.2,33.7,17.3,23.2,33.7,15.1,19.0 and 23.9 mm,respectively.The ridge-furrow rainwater harvesting with biochar application increased topsoil temperature at the ridge tops.This increased topsoil temperature at the ridge tops trasmited to furrow bottoms,and the high plant ground shading decreased soil temperature at furrow bottoms in summer.Compared to FP during the sainfoin growing seasons,the increase of topsoil temperature at the ridge tops for MCS₃₀,MCS₄₅,MCS₆₀,MSB₃₀,MSB₄₅,MSB₆₀,CDB₃₀,CDB₄₅ and CDB₆₀0 was 0.9,1.4,2.0,1.5,1.9,2.5,1.5,2.0 and 2.6°C,respectively.The ridge-furrow rainwater harvesting with biochar application improved soil water and heat conditions,leading to high soil nutrients content.MCS did not significantly change soil pH and soil nutrients content,even though ridge width increased.Compared with FP,the soil pH increased by 0.5 for both MSB and CMB treatments.The soil organic matter content increased by15.2%and 18.4%for MSB and CMB,respectively,for the same treatments.The soil total nitrogen content similarly increased by 23.2%and 24.7%for both MSB and CMB treatments trespectively.For the same treatments,the soil available phosphorus content increased by 15.0%and 16.7%,and the soil available potassium content increased by 9.1%and10.6%.Sainfoin roots and nodules were mainly distributed in soil surface layer?0-20 cm?,and the values of roots and nodules characteristics increased as ridge width increased,and decreased as soil depth increased.The study revealed that the suitable soil water content in the furrow profile resulted in an increase of root dry matter,root number and root nodule weight,whereas the suitable drought stress resulted in an increase of root length,root surface area,and root volume of sainfoin plants.The ridge-furrow rainwater harvesting improved soil water,heat and nutrients conditions,leading to high plant growth,biomass formation and WUE.Compared with FP,the WUE increased by 11.0,13.5,16.1,20.2,28.4,33.5,16.8,22.1 and 25.5 kg ha^-1 mm^-11 for MCS₃₀,MCS₄₅,MCS₆₀,MSB₃₀,MSB₄₅,MSB₆₀,CDB₃₀,CDB₄₅5 and CDB₆₀,respectively.The forage yields of sainfoin decreased by 6.5%,12.1%and 13.8%for MCS₃₀,MCS₄₅5 and MCS₆₀,respectively,the forage yields of sainfoin increased by 19.7%,24.4%,22.5%,8.0%,8.9%and6.8%for MSB₃₀,MSB₄₅,MSB₆₀,CDB₃₀,CDB₄₅5 and CDB₆₀,respectively.The optimum ridge width for MSB was 49 cm,whereas that of the CDB was 41 cm.The ridge-furrow rainwater harvesting with biochar application increased sainfoin tannins content and crude protein content,but decreased the neutral detergent fiber content and acid detergent fiber content,which did not significant change with ridge width increase.Compared with FP,the sainfoin tannins content increased by 4.44%,13.97%and 9.09%for MCS,MSB and CDB,respectively.For the same treatments,the crude protein content decreased by 30.81%,40.66%and 39.33%,respectively,whereas the acid detergent fiber content decreased by 4.00%,11.15%,8.40%.The neutral detergent fiber content decreased by 5.71%,13.34%and 11.60%,respectively.MCS did not significantly change the calcium and phosphorus contents.Compared with FP,the calcium contents increased by 31.20%and 27.00%for MSB and CDB,respectively,for the same treatments,the phosphorus contents increased by 23.15%and 19.86%,respectively.Forage quality of sainfoin were evaluated by the Grey Incidence Degree Analysis,and the weighted correlation degree was in order of MSB₆₀>MSB₄₅>CDB₆₀>MSB₃₀>CDB₄₅>CDB₃₀>MCS₆₀>MCS₄₅>MCS₃₀>FP.The ridge-furrow rainwater harvesting with biochar application improved sainfoin yield,and quality and WUE,especially the ridge-furrow rainwater harvesting with maize straw biochar application.