Effects of field slope and duration of furrow irrigation on growth and yield of six grain-legumes on a waterlogging-prone vertisol

Abstract

The effects of field slope and duration of furrow irrigation on the growth and yield of six grain-legume species were compared on a waterlogging-prone Vertisol (Typic Pellustert) at Narrabri, N.S.W., Australia. The species were soybean ( Glycine max L.) Merr.), navy bean ( Phaseolus vulgaris L.), pigeon pea ( Cajanus cajan (L.) Millsp.), adzuki bean ( Vigna angularis (Willd.) Ohwi and Ohashi), cowpea ( V. unguiculata (L.) Walp.) and mung bean ( V. radiata L.). Field slopes of 1:500, 1:1000, 1: 1500 and 1:2000 were factorially combined with durations of furrow irrigation of 4, 16 and 32 h irrigation −1 in order to vary the severity of waterlogging and assess the relative sensitivities of the six species. Treatments were applied at each of four irrigations. Growth of all species was reduced by increasing the duration of irrigation at the first irrigation, but the more tolerant species became less affected as they developed. Grain-yields of soybean (2.41 t ha −), and cowpea (1.72 t ha −1) were not significantly affected by treatments. However, increasing the duration of irrigation from 4 or 16 h to 32 h reduced the yield of pigeon pea and mung bean by 12%, adzuki bean by 15% and navy bean by 45%. The last four species yielded 2.03, 1.90, 1.14 and 1.18 t ha −1, respectively, at the optimum field slope (1:1000) and duration of irrigation (4 or 16 h). Nitrogen uptake in the harvested grain of soybean (122 kg ha −1) was 2–5 times that of the other species. Reductions in the concentration and uptake of nitrogen of affected species implied that nitrogen fixation or nutrient absorption were inhibited by waterlogging. The study demonstrated that in a semi-arid, sub-tropical environment, a field designed and managed to ensure adequate drainage of excess irrigation water can restrict waterlogging to a period of 1–2 days per irrigation in the surface 0–0.2 m of cropped ridges, enabling sensitive species to survive, grow and produce appreciable quantities of grain.