| Drought and soil erosion are the main factors restricting grain production and economic development in the semiarid hilly area of Loess Plateau.Steeply sloping lands are the main sources of runoff and sediment loss in this area.Our work sought to optimize a tied-ridging tillage system,which has good water retention and soil erosion control.Two field experiments were conducted in Anjiagou Catchment in Dingxi,Gansu province,China.The purpose of the first experiment was to investigate the quantity of runoff and the threshold rainfall needed to produce it for different ridge slopes?0°,5° and 10°?on standard ridges.The second field experiment was designed to investigate the effects of different tillage systems?ridging without ties and tied-ridging?on runoff storage efficiency,overall system efficiency,plot runoff efficiency,sediment loss,soil nutrient loss,soil water storage,fodder yield,water use efficiency?WUE?and quatity on 2 slopes?5° and 10°?,using traditional flat planting?TFP?as a control.Average annual runoff efficiency for standard ridges(15-20 cm height and 45 cm width)with slopes of 0°,5° and 10° was 70.6%,78.5% and 88.4%,respectively.The threshold rainfall needed to produce runoff for the same treatments was 0.46,0.71 and 0.22 mm,respectively;and average runoff efficiency was 83.5%,97.6% and 96.4% by analysis of regression results.Average runoff storage efficiency for slopes of 5° was 87%,92% and 94% for TFP,ridging without ties and tied-ridging,respectively,during the alfalfa growing seasons;the overall system efficiency was 0%,78% and 80%,respectively.Average runoff storage efficiency for slopes of 10° was 86%,91% and 93% for TFP,ridging without ties and tied-ridging,respectively;the overall system efficiency was 0%,83% and 85%,respectively.The average runoff storage efficiency for slopes of 5° was 91%,similar to that for slopes of 10°?90%?.The overall system efficiency for slopes of 5° was 53%,slightly less than that of a 10° slope?56%?.Average plot runoff efficiency for slopes of 5° was 11.6%,9.2% and 6.7% for TFP,ridging without ties and tied-ridging,respectively.Average plot runoff efficiency for slopes of 10° was 14.1%,10.0% and 7.8% for TFP,ridging without ties and tied-ridging,respectively.The plot runoff efficiency for slopes of 5° was 1.2 times of that for a slope of 10°.Sediment loss for slopes of 5° decreased by 80.8% and 83.3% for ridging without ties and tied-ridging,respectively,compared with TFP.Sediment loss for slopes of 10° decreased by 74.5% and 82.0% for ridging without ties and tied-ridging,respectively,compared with TP.Sediment loss for slopes of 10° was 1.2 times that for slopes of 5°.Nitrogen,phosphorus,potassium and organic matter loss for slopes of 5° decreased by 81.0%,80.9%,80.9% and 78.2% for ridging without ties,respectively,compared with TFP;while decreased by 83.4%,83.3%,83.4% and 81.1% for tied-ridging.Nitrogen,phosphorus,potassium and organic matter loss for slopes of 10° decreased by 81.5%,74.8%,73.6% and 61.5% for ridging without ties,respectively,compared with TFP;while decreased by 87.1%,82.0%,81.6% and 72.4% for tied-ridging.Loses of phosphorus,potassium and organic matter for slopes of 10° were 1.2 times that for slopes 5°,and nitrogen loss for slopes of 10° was 1.5 times that for slopes of 5°.Average soil water storage for slopes of 5° increased by 9.3 and 15.0 mm for ridging without ties and tied-ridging,respectively,compared with TFP;Average soil water storage for slopes of 10° increased by 11.2 and 16.2 mm for ridging without ties and tied-ridging,respectively,compared with TFP.Average soil water storage for slopes of 5° was 4.3 mm higher than that for slopes of 10°,during the alfalfa growing seasons.Soil water storage for slopes of 5° increased by 21.0,16.7 and 11.5 mm for upslope,mid-slope and downslope,respectively,compared with that for slopes of 10°.Soil water storage was in order of upslope < mid-slope < downslope and upper furrow > mid-furrow > lower furrow after rainfall,especially heavy rainfall.Fodder yield of alfalfa for slopes of 5° increased by 20.4% and 8.9% for ridging without ties and tied ridging,respectively,compared with TFP.While WUE increased by 4.78 and 4.58 kg hm-2 mm-1,but economic value decreased by 12.5% and 46.1%.Fodder yield of alfalfa for slopes of 10° increased by 22.4% and 9.0% for ridging without ties and tied ridging,respectively,compared with TFP.While WUE increased by 4.89 and 4.06 kg hm-2 mm-1,but economic value decreased by 9.9% and 51.6%.The differences of fodder yield and WUE of alfalfa between slopes 5° and slopes 10° were not clear.The content of crude protein,crude fat,neutral detergent fiber,acid detergent fiber,calcium and phosphorus for slopes of 5° increased by 23.0%,28.8%,33.4%,20.3%,11.0% and 55.4% for ridging without ties,respectively,compared with TFP,while increased by 15.2%,19.9%,28.4%,21.9%,5.5% and 43.7% for tied ridging.The content of crude protein,crude fat,neutral detergent fiber,acid detergent fiber,calcium and phosphorus for slopes of 10° increased by 30.6%,34.6%,36.6%,19.3%,12.9% and 37.2% for ridging without ties,respectively,compared with TFP,while increased by 23.0%,17.6%,24.2%,30.0%,10.2% and 23.2% for tied ridging.The differences of fodder quality of alfalfa between slopes 5° and slopes 10° were not clear.In the semiarid hills of the Loess Plateau,ridge-furrow rainwater harvesting had good water and soil conservation with increase in fodder yield.Tied-ridging rainwater harvesting was particularly effective at water and soil conservation,while ridging without ties was particularly effective at increasing fodder yields. |
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