Effect of Plant Spacing and Rhizobial Inoculation on Growth, Nodulation and Yield of Selected Greengram Varieties in Kiboko and Ithookwe in Lower Eastern Kenya

Abstract

Diseases, pests, inappropriate agronomic practices and drought are the most important constraints to grain legumes production in Sub-Saharan Africa. Low green gram Vigna radiata (L) Wilczek yields in eastern Kenya is attributed to lack of adequate knowledge of agronomic practices like fertilization, appropriate spacing and use of available high yielding varieties. Therefore, the current study was established in Kiboko and Ithookwe to evaluate the influence of intra row spacing and microbial inoculation and varieties on growth and yield of selected green gram varieties. Five levels of plant spacing (5 cm x 45 cm, 10 cm x 45 cm, 15 cm x 45 cm, 20 cm x 45 cm, 25 cm x 45 cm), two inoculation treatments (inoculated with rhizobia and not inoculated with rhizobia) and three green gram varieties (KS20, KAT 00308 and KAT 00309) which were laid out in a randomized complete block design with a factorial arrangement and replicated three times. Data was collected on growth and yield parameters and analysed using GenStat Version 15.1 and means separated using Fischer’s Protected LSD test at p≤0.05. Plant height, shoot dry weight, number of effective nodules, weight of nodules and the ground cover were significantly influenced by the intra-row spacing in both sites but no significant differences observed on the parameters due to rhizobial inoculation. The days to maturation were significantly different between the intra-row spacing treatments in both sites where the narrowest spacing led to earlier maturation of green grams. The varieties differed significantly on plant height, shoot dry weight, number of effective nodules, dry weight of nodules and the ground cover in both sites. Variety KS20 matured the earliest in Kiboko while KAT00309 matured within the shortest period in Ithookwe where the two sites had a difference of >11 days. There were significant differences between the intra-row spacing treatments in growth parameters where the highest grain yield at Kiboko (3,114 kg ha-1) was observed in the 20 cm by 45 cm spacing while the same treatment had the highest grain yield at Ithookwe (1,583 kg ha-1). The lowest grain yield was exhibited in the narrowest spacing of 5 cm by 45 xv cm spacing in both sites. Inoculation significantly increased the number of effective nodules compared to those that were not inoculated in both sites at 3, 5 and 7 weeks after sowing (WAS) but it did not have a significant influence on the yield of green gram. The varieties differed significantly in the growth and yield parameters tested in both sites where variety KAT00309 had the highest grain yield with 2,898 kg ha-1 and 1,568 kg ha-1 in Kiboko and Ithookwe respectively. The local variety, KS20 had the lowest number of pods per plant in both sites with only 22 and 14 pods per plant for Kiboko and Ithookwe respectively compared to 33 and 20 pods per plant on the other varieties in Kiboko and Ithookwe respectively. Moreover, the local variety had the lowest 100-seed mass at the two study sites with more than 14% compared to KAT00308 and KAT00309. From these results, it is recommended that variety KAT00309 is the best variety in both sites planted at an intra-row spacing of 20 cm by 45 cm with or without inoculation.