| dc.description.abstract | Soil fertility decline is one of the major constraints in agricultural productivity. Biological nitrogen
fixation (BNF) in legumes can offer a cost-effective and sustainable means towards soil fertility
management. There is limited information on green-gram BNF enhancement through Rhizobium
inoculation with rock phosphate fertilizer. The objective of this study was to determine the effects of
Rhizobium and rock phosphate fertilizer application on soil chemical properties under green-gram
varieties. The study was carried out at Chuka university horticultural research farm in two seasons
(November 2019 - January 2020 and February - April 2020). A factorial experiment of 2 x 2 x 2 was
laid out in a randomized complete block design (RCBD). There were three factors; varieties (N26
and KS20), rock phosphate (0 and 30 kg P ha-1
) and Rhizobium inoculation (0 and 100 g ha-1
)
making a total of eight treatments which were replicated three times. Soil sampling and analyses
were done for soil pH, fixed-N, total nitrogen (TN), exchangeable cations (EC), available
Phosphorous (P), total organic carbon (TOC), and exchangeable potassium (K) before planting
and after harvesting of green-grams for the two seasons. Data was analysed using GENSTAT 15th
edition (P≤0.05). Results from both seasons indicated that combined application of rock phosphate
at 30 kg P ha-1 and Rhizobium inoculation at 100 kg ha-1 showed significant (P≤0.05) higher increase in soil chemical properties over other treatments. However, treatment R1P1KS20
recorded significantly higher results in soil pH (7.54), TN (0.58%), TOC (3.45%), P (68.20 ppm)
and EC (0.95 CmolKg-1
), fixed-N (0.50%) and K (1.75 CmolKg-1
). On the other hand treatment
R0P0N26 recorded significant (P≤0.05) lower results in soil pH (5.23), TN (0.04%), TOC (1.86%),
P (8.76 ppm), EC (0.21 CmolKg-1
) and K (0.58 CmolKg-1
). Therefore, Rhizobium inoculation in
green-grams in combination with rock phosphate is an important legume nitrogen fixation
enhancement method. This method is cost effective for farmers in sustainably supplementing
nitrogen and phosphorous in their farms for improved soil fertility management. Based on the
findings, combining Rhizobium 100g ha-1 and rock phosphate 30 kg P ha-1 with variety KS20 were
recommended for a sustainable soil fertility management in Tharaka Nithi County. | en_US |
