| Drought, water loss and soil erosion are main factors constraining agricultural production in semi-arid Loess Plateau regions of C hina. In order to improve field soil water content and increase utilization of rainwater resources, field experiments were conducted to determine(1) Runoff efficiencies and threshold rainfalls of different ridge widths(30, 45 and 60 cm) mulched with different materials(common plastic film, biodegradable mulching film and manual compacted soil) and(2) the effects of different ridge–furrow ratios(30:60, 45:60 and60:60) and ridge- mulching materials on soil water storage, topsoil temperature, forage yield and nutrient, grain yield, yield components, water use efficiency(WUE) and economic benefits of oats in ridge–furrow rainwater harvesting(RFRH) system at the Dingxi Agri-meteorological station.Results of runoff observation field experiment were as followed. Annual runoff efficiency(expressed as a ratio of runoff to rainfall received at the same period) were 17.5%, 18.2%, 22.2%, 70.8%, 77.8%, 82.6%, 76.6%, 79.8% and 85.7% for SR30, SR45, SR60, BMR30, BMR45, BMR60, CMR30, CMR45 and CMR60(SR, BMR and CMR were ridges with compacted soil, covered with biodegradable mulch film and common plastic film, respectively, and subscript 30, 45 and 60 refer to ridge widths(cm) all with 60 cm furrow width), respectively. While those analyzed by regression equation were 32.5%, 32.7%, 36.8%, 89.1%, 89.2%, 93.5%, 90.8%, 90.5% and 95.2% and average monthly runoff efficiencies were 17.4%, 18.0%, 22.0%, 70.1%, 77.0%, 81.8%, 75.9%, 79.0% and 84.8% during Oats growing season in 2012. The runoff collected into furrows was 34.6, 35.9, 43.8, 139.4, 153.3, 162.7, 151, 157.2 and 168.8 mm for SR30, SR45, SR60, BMR30, BMR45, BMR60, CMR30, CMR45 and CMR60, respectively. Rainfall of more than 5 mm is considered to be effective, but for SR30, SR45, SR60, BMR30, BMR45, BMR60, CMR30, CMR45 and CMR60, threshold rainfall was 4.5, 4.5, 44, 3.4, 3.3, 3.2, 3.3, 3.3 and 3.2 mm, respectively.Results of Oats production under RFRH system were as followed. Compared with TP(traditional planting), average increase in soil water storage during Oats growing season was 7.1, 12.9, 19.6, 15.5, 22.8, 34.2, 17.2, 26.7 and 35.3 mm for SR30, SR45, SR60, BMR30, BMR45, BMR60, CMR30, CMR45 and CMR60, respectively. Soil water storage changes after rainfall was in order of BMR ≈ CMR > SR, at furrow sides and furrow middles, while this was BMR ≈ CMR > SR, at ridge tops.In oats trials, ridge mulching and ridge width had distinct effects on topsoil temperature at ridge tops, but not at furrow bottoms. Compared with TP, average increase topsoil temperature at ridge tops during Oats growing season was 2.0, 1.9, 1.6, 4.0, 4.7, 4.2, 5.2, 5.1 and 4.7 ℃ for SR30, SR45, SR60, BMR30, BMR45, BMR60, CMR30, CMR45 and CMR60, respectively. As measured around 8:00 am, topsoil temperature decreased from 0 cm to 10 cm, and increased from 10 cm to 25 cm. And as measured around 2:00 pm and 6:00 pm, topsoil temperature decreased with soil depth increasing. Soil temperature difference between different mulching materials was the maximum as measured around 2:00 pm, compared with measuring around 8:00 am and 6:00 pm. Compared with SR45, average soil temperature increases at ridge tops were 3.8 and 4.9 ℃ for BMR45 and CMR45, respectively. Soil temperature difference at ridge tops was higher than that at furrow bottom.Compared with TP, average Oats forage yield decrease was 5%, 10%, 20% and 2% for SR30, SR45, SR60, BMR60, respectively, while increase was 11%, 5%, 16%, 6% and 0% for BMR30, BMR45, CMR30, CMR45 and CMR60. Average forage crude protein increases of Oats was 4%, 23%, 28%, 10%, 30%, 33%, 31%, 27% and 33% for SR30, SR45, SR60, BMR30, BMR45, BMR60, CMR30, CMR45 and CMR60, respectively. While average forage neutral detergent fiber decrease was 0.2%, 2.2%, 2.9%, 0.1%, 0.2%, 2.9%, 5.5%, 7.8% and 8.6%.Compared with TP, average Oats grain yield decreased by 11%, 19% and 25%, while the WUE increased by 41%, 50% and 57% for SR30, SR45, SR60, respectively. And average grain yield increased by 5%, 4%, 2%, 11%, 9% and 7%, while WUE increased by 42%, 52%, 59%, 49%, 58% and 66% for BMR30, BMR45, BMR60, CMR30, CMR45 and CMR60, respectively. Optimum ridge width was 34 cm, which gave the highest grain yield(2114 kg ha-1) for BMR. And was 38 cm, which gave the highest grain yield(2213 kg ha-1) for CMR in Oats production under the RFRWH system with 60 cm furrow width, when rainfall was more than 206.4 mm in semi-arid areas of Northwest China.Economic benefits decreases were 305 and 748 RMB ha-1 for BMR, when compared with TP and CMR, and increase was 332 RMB ha-1 when compared with SR. Bio-degradable mulching film had similar benefits on soil water retention, soil temperature, and forage yield as common plastic film for early crop growth. It is unnecessary to collect the residue of Bio-degradable mulching film after crops harvesting. It has benefit for time and labor saving, and environmental protection. |
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