Data on long-term effects of tillage, phosphorus fertilization and crop rotation on pearl millet–cowpea productivity in the West-African Sahel

The experiment was established in 1986 and continued until 2018 at the ICRISAT Sahelian Center (ISC), located at Sadore, 45 km south of Niamey, Niger, West Africa (lat 13" l5'N long 2' 18'E) and at an altitude of 240 m asl. The climate at Sadore is characterized by a short rainy season from June to September (about 90 d). The average rainfall is 560 mm, is irregular and normally comes in the form of thunderstorms. During the crop growing season, maximum temperatures varied in the range of 30-40oC. Potential evapotranspiration (PET) exceeds the total rainfall in all months except July-August which are the peak months of the rainy season (Sivakumar, l986). The site is located on a sandy plain with Aeolian sands 2-8 m in depth covering one of a series of stepped surfaces comprised of cemented laterite gravels (West et al., l984). The surface horizon (25-30 cm in depth) is yellowish red sand underlain by a thick (> 1m) red loam or red sand horizon. Soils are coarse textured, with sand content exceeding 95%. Organic matter content is about 0.4%. The soils are acidic in nature (pHH2O 4.5-5.0), and low in nutrients (cation exchange capacity: 1.5 cmol kg-1) and water holding capacity (< 10%) (West et a1., 1984). The experiment was designed as a randomized complete bock (RCBD) with l3 treatments (Table 2), replicated four times, involving various combinations of hand cultivation (HC), ridging with animal traction and planting on ridges (AT), limited P fertilizer application and rotation with sole cowpea (C). These were tested with two cropping systems: millet-cowpea intercrop (M/C) and sole millet (M). Plot size was 500 m2 150 m x l0 m), and the area sampled for yield of each experimental plot was 75 m2 125 m x 3 m). In 1989, an additional treatment of crop residues (millet straw) was introduced by dividing each treatment plot into half. Thus, the plot size was reduced to half (250 m2, 25 m x l0 m), and similarly the sampled area became half (37.5 m2, 12.5 m x 3 m). In 1994, nitrogen treatment (15 kg N ha-1 as calcium ammonium nitrate) was introduced by further dividing each experimental plot into two, thereby creating additional treatments with nitrogen and without nitrogen. Experimental location on Google Maps

本试验于1986年设立，持续至2018年，场地位于西非尼日尔尼亚美以南45公里的萨奥雷（Sadore）的国际半干旱热带作物研究所（ICRISAT）萨赫勒中心（ISC），地理坐标为北纬13°15′、东经2°18′，海拔240米。萨奥雷地区的气候特点为6月至9月的短雨季（时长约90天），年均降雨量560毫米，降雨分布不均且多以雷暴形式出现。作物生长期内，最高气温介于30~40℃之间。除雨季峰值月份7-8月外，其余各月的潜在蒸散量（Potential Evapotranspiration, PET）均高于同期总降雨量（Sivakumar, 1986）。试验场地坐落于沙质平原，表层覆盖厚度2~8米的风成砂，属于一系列由胶结红土砾石组成的阶梯状地表之一（West et al., 1984）。地表层（深度25~30厘米）为黄红色砂质土层，其下为厚度大于1米的红色壤土或红色砂质土层。土壤质地偏粗，砂粒含量超过95%，有机质含量约0.4%，呈酸性（pH(H₂O) 4.5~5.0），养分含量较低（阳离子交换量：1.5 cmol·kg⁻¹），持水能力不足10%（West et al., 1984）。本试验采用随机完全区组设计（Randomized Complete Block Design, RCBD），共设13个处理（见表2），重复4次，涵盖人工耕作（Hand Cultivation, HC）、畜力起垄并垄上种植（Animal Traction Ridging and Ridge Planting, AT）、限量施磷肥以及与单作豇豆（Cowpea, C）轮作等多种组合。试验设置两种种植系统：粟-豇豆间作（Millet-Cowpea Intercrop, M/C）与单作粟（Sole Millet, M）。试验小区面积为500平方米（50米×10米，原标注为150米×10米，疑似输入笔误），每个试验小区的产量采样面积为75平方米（25米×3米）。1989年，新增作物残体（粟秸秆）处理：将每个处理小区均分为两半，因此小区面积缩减至250平方米（25米×10米），对应采样面积也减半为37.5平方米（12.5米×3米）。1994年，增设氮肥处理（每公顷施15千克氮，以硝酸铵钙形式施加）：将每个试验小区再次均分为两份，由此形成施氮与不施氮的额外处理。可通过谷歌地图查看试验点位。