Effect Of Direct Seeding And Transplanting On Growth And Yield Of Selected Rice (Oryza Sativa L.) Varieties On Rain-Fed And Irrigated Lowlands Of Kenya

Abstract

Constraints to optimal rice productivity in Kenya include shortage of water, unavailability of affordable labour, inappropriate agronomic practices in establishment like spacing, plant nutrition, weeds, diseases and insect pests. About 95% of rice production in Kenya is grown under irrigation where farmers raise seedlings in nurseries before transplanting to the main fields. Irrigated rice requires large amounts of water for field operations, subject farmers to drudgery during transplanting and also incurs extra costs in nursery and transplanting. A better understanding of a cost effective method of crop establishment of improved rice varieties will save on labour, reduce associated drudgery and also reduce amount of water wasted in flooded conditions without compromising on grain yields. Previous studies have not clearly stated comparisons between direct seeding and transplanting for rain-fed and irrigated rice varieties on lowland conditions. An experiment was conducted at Ahero and Mwea to assess the effect of direct seeding (DS) and transplanting (TP) method of crop establishment on growth and yield of four rain-fed (NERICA 1&4, Komboka, MWUR4) and four irrigated (SARO5, Komboka, NIBAM 11, MWIR 2) rice varieties, during main rice cropping season between July 2017 and January 2018 on Kenyan lowland environment. The trials objectives were to assess the effect of direct seeding and transplanting on crop growth and yield of rain-fed and irrigated rice varieties, in addition to labour saving practices during establishment. Design used was a randomized complete block design (RCBD) with treatments on a split plot arrangement, three replicates, with establishment method as main plot (4m x 3m) and variety as subplot. Three (3) seeds hill-1 were dibbled and later thinned to one on DS plots while one seedling was transplanted on TP plots. Spacing 20cm x 15cm for both direct seeded and transplanted plots was used. Data was subjected to analysis of variance (ANOVA) and separation of means using protected LSD at 5% probability level whenever there was significant difference. Results on rain-fed varieties for plant height, number of productive tillers hill-1, days to flower onset, and number of unfilled grains hill-1 were not significantly (P> 0.05) effected by method of crop establishment though significant (P< 0.05) effects were confirmed across varieties and on site location on these crop factors. Grain yield (t ha-1) and thousand seed weight (g) means were not significantly P> 0.05) affected by method of crop establishment, site location and across varieties. However, Komboka (5.3 t ha-1) and MWUR4 (4.6 t ha-1) were highest and lowest respectively on grain yield among rain fed varieties. Irrigated varieties recorded significant (P< 0.05) differences in number of productive tillers hill-1 and days to flower on set under direct seeding and transplanting. Significant variations also existed on plant height, number of productive tillers hill-1, number of unfilled grains hill-1, 50% and 100% days to flower onset across the sites and among tested varieties. In contrast, grain yield (t ha-1) and 1000 seed weight (g) were statistically (P> 0.05) similar and not influenced by method of crop establishment and similarly not affected among tested varieties and across the sites. Nevertheless, MWIR2 had highest grain yield mean at 6.3 t ha-1 and lowest mean was on NIBAM 11(4.8 t ha-1) among irrigated varieties. Total variable costs were higher on transplanted (KES 84,850) compared to direct seeded (KES 60,300) crop. Although direct seeding method of crop establishment yielded lower compared to transplanting, on both rain-fed and irrigated varieties, savings on variable costs would motivate its wide adoption. Rain-fed Komboka and irrigated MWIR2 exhibited better growth and yield factors and thus would be recommended for Mwea and Ahero lowlands.