Early Sowing of Grain Legume Crops after Rice Harvest Increases Grain Yield

Abstract

Most paddy fields in Timor Leste are abandoned after harvesting the rice crop due to limited supplemental irrigation. Other field studies have identified some drought-adaptive grain legumes including kidney bean (previously grown in cold, highland areas only), Ceora grass pea (Lathyrus sativus L., a newly introduced species), mung bean, and soybean for growing after rice harvest. The impact of sowing date on growth and yield after rice harvest is not well understood. The current study aimed to identify the appropriate sowing time of grain legumes after rice harvest. Seeds of kidney bean and grass pea were sown in plots arranged in a randomized block design with three factors (species, drought treatment, and sowing date) and three replications. There were three sowing dates at monthly intervals: 28 May (D1), 28 June (D2) and 28 July 2017 (D3). The terminal drought treatment was applied at first flower of grass pea or pod set of kidney bean for each sowing date. Overall, kidney bean produced more seed yield (32% higher) than grass pea. Yields of both species decreased at the later sowing dates (P<0.001). Grass pea produced 78% more filled pods than kidney bean, but 34% fewer seeds per pod and 58% smaller seeds than kidney bean. Seed weight in both species decreased at later sowing dates as did seeds per pod in kidney bean, but grass pea maintained seed numbers per pod at all sowing dates. Dry matter production between species was comparable, which declined at later sowing dates (P<0.001). In conclusion, early sowing of grain legumes produces more seeds and biomass after rice harvest than late sowing.