The effect of cow manure combined with foliar sprays of black jack (Bidens pilosa L.) and comfrey (Symphytum officinale L.) leaf extracts on the growth, yield and nutritional quality of common bean (Phaseolus Vulgalis L.)

Common bean (Phaseolus vulgaris L.) is important legume crop for nutritional and food security in Kenya. Declining soil fertility in small holder farms, as a result of limited or non-application of inorganic fertilizer, because of rising costs, has resulted in low production. The aim of the study was to investigate the effect of cow manure combined with foliar sprays of black jack (Bidens pilosa L.) and comfrey (Symphytum officinale L.) extracts on growth, yield and nutritional quality of common bean. A 4 x 6 factorial experiment in a randomized complete block design (RCBD) with 3 replicates was conducted in Egerton University’s research Field 7 for two cropping seasons. Four fertilizer levels were 0, 5, 10 t ha-1 of cow manure and 148.15 kg ha-1 NPK (27-27-27) fertilizer, as a positive control. In addition, six foliar spray treatments; no spray (control), comfrey spray applied once(C1) or twice weekly(C2), black jack spray applied once(B1) or twice (B2) weekly and commercial Easy Grow spray (EG) (positive control), applied every 14 days at the rate of 3 kg ha-1 were used. Soil samples were collected before the experiment set up for analysis of initial chemical and physical properties. Data on yield parameters, including harvest index, hundred seed weight, yield per ha-1, and protein content in seeds were collected at harvest. The Shapiro-Wilk test was used to ascertain the normality of data and analysis of variance was performed using Proc GLM in Statistical Analysis Software (SAS). Tukey’s Honestly Significant Difference was used to compare the means at P<0.05. Compared to lesser manure rates, treatment M2 (10 t ha⁻¹) of cow manure performed better than other manures and control, it produced taller plants, more branches, higher biomass, great pod number, high seed weight, and yield than the control and lower manure rates. The effects of foliar spraying varied by stage; at the V4 stage, comfrey once a week (C1) and Black Jack sprayed twice a week (B2) increased plant height and the leaf area index, while C2 (comfrey twice a week) produced the most grain. The combination of M2 and C2 produced the maximum yield (2373.88 kg ha⁻¹), which can be recommended for beans production.