Improving Cowpea Production using Humates and Seaweed extract bio-stimulators

Abstract

A study was carried out in Jomo Kenyatta University of Agriculture and Technology, Juja and Kenya Agricultural and Livestock Research organization (KALRO) Katumani to evaluate the effect of bio-stimulators; seaweed extracts of Ecklonia maxima and potassium humates, on four cowpea varieties K80, Kenya Kunde, KVU 27-1 and M66 for leaf and seed production from March to August 2013 and short rain season 2014/15. The treatments were designed in factorial structure laid out in randomized complete block design and replicated thrice. The plots measured 2.5m by 2.5m at a spacing of 60cm by 20cm. Bio-stimulators were applied in planting holes except seaweed extracts foliar spray which was applied after emergence to flowering. Treatments were nine (humates, seaweed extracts (SWE), biofix, control, humates+SWE basal application, humates+SWE basal application+SWE foliar spray, humates+SWE foliar spray, SWE basal application+SWE foliar spray and SWE foliar spray) and the four cowpea varieties. Data was obtained for rate of emergence, days to emergence, survival rate, plant height, stem thickness, root length and nodule formation, number of leaves produced, leaf weight, leaf area and chlorophyll levels. The experiment for cowpea seed production was split plot design, with cowpea varieties as the main plots while bio-stimulators as sub-plots, replicated 6 times. The plots measured 2m by 2m, at a spacing of 60 cm by 20 cm. Treatments included SWEs, humates, biofix and control. Data was obtained fordays to flowering, days to podding, number of pods, length of pods, number of seeds per pod and total weight of seeds produced per plot. The data was taken every week and recorded in Microsoft excel sheet, where it was cleaned, organized and subjected to analysis of variance. Treatments which showed significance were separated using Fischer’s Protected LSD at 95%. Rate of emergence, days to emergence, survival rate, plant height, chlorophyll levels, leaf weight, stem thickness (weeks 1, 3, 6 and 8), root length (week 8), nodules formed (weeks 6 and 8) and number of cowpea leaves formed were significantly different between Juja and Katumani but not in leaf area at p≤0.05. Highest rate of emergence (61%), survival rate (70 plants), chlorophyll levels (54.4), leaf area (50.7cm2), longest roots and highest number of nodules formed (week 6 and 8) were in Juja and highest leaf weight (2.5g) and earliest emergence of 4 days were recorded in Katumani. Bio-stimulators were significantly different in rate of emergence, days to emergence, survival rate, leaf area, plant height (weeks 2, 4 and 5), root length (week 5), nodules formed (weeks 5 and 8) and number of leaves formed but not in chlorophyll levels, leaf weight and stem thickness at p≤0.05. In Juja, humates caused high emergence rate, high survival rate, higher plant height and improved number of leaves whereas in Katumani, it improved leaf weight and high number of nodules formed in week 8 compared to control. SWE basal application+SWE foliar spray caused early emergence, high rate of emergence and survival rate, enhanced chlorophyll levels, higher leaf weight and longer roots besides improving cowpea leaf production in Katumani and in Juja, longer roots and high number of nodules. Humates+SWEs caused early germination, high cholorophyll levels and higher number of nodules formed in Juja. K80 had the highest rate of emergence, survival rate, leaf weight and area. In addition, K80 produced the highest number of leaves from week 3 to 8 in Juja (315, 784, 1036, 1424 and 2139) while in Katumani, Kenya Kunde produced the highest number of leaves in weeks 3 and 5 (211, 417), KVU 27-1 in weeks 4 and 6 (361, 436) and K80 in week 8 with 618. In cowpea seed production, there were significant differences between bio-stimulators in number of pods, length of pods, number of seeds produced per pod and total weight of seeds but not in days to flowering neither were there any interactions between bio-stimulators and varieties at p≤0.05. Varieties were significantly different in days to podding and length of pods but not in number of pods formed, number of seeds per pod or total weight of seeds formed at p≤0.05. KVU 27-1 and K80 produced the highest number of seeds and pods in humates while M66 and K80 produced the longest pods and highest seed weight in SWEs respectively. Based on findings from this study, use of seaweed extracts and potassium humates is recommended to boost cowpea leaf and seed production in marginal areas. Further work should investigate the potency of nodules formed in marginal areas under water stress conditions and use of bio-stimulators with fertilizers to boost vegetable production.