Effect of Tithonia diversifolia (Hemsley) and inorganic fertilizers on maize yield on Alfisols and Ultisols of western Kenya

Abstract

Smallholder maize (Zea mays L.) farmers cannot cope with the high and ever increasing prices of fertilizers, resulting in continuous low grain yield, chronic food shortage and insecurity. Cheaper, sustainable alternatives of improving soil fertility are being sought. The influence of Tithonia diversifolia (Hemsley) A. Gray and fertilizer application on maize yield was studied on N and Pdeficient Alfisols and Ultisols in western Kenya. An on-farm trial, consisting of six treatments: farmer's practice, N (60 kg ha-1), NP (60 kg ha-1 of each), NPK (60 kg ha-1 of each N and P; K 40 kg ha-1), tithonia+30 kg N ha-1, and optimal fertilizer (N, 200; P, 60; K, 120; Mg, 20; B, 5 kg ha-1), arranged in a Randomized Complete Block Design, with five replications in each soil type was set-up during wet and dry seasons of 2006. During the wet season, Alfisols gave about 80% more grain yield compared to Ultisols. Treatment comparison within Alfisols indicated that tithonia had a 102% yield advantage over farmer's practice; but optimal fertilizer, NPK, NP and N had yield advantage of 56%, 6%, 4% and 4%, respectively, over tithonia. Apart from optimal treatment, all other fertilizer treatments were not significantly different (P0.05) on grain yield. Within Ultisols, tithonia had a 96% grain yield advantage over farmer's practice; treatments optimal fertilizer, NPK, NP and N had yield advantage of 76%, 25%, 10% and 7%, respectively, over tithonia. Again NP and N were not significantly different (P0.05) from tithonia on grain yield. During the dry season, Ultisols gave 17% more grain yield than Alfisols. Comparison within Alfisols indicated that tithonia had a yield advantage of 30%, 30%, and 13% over N, NP and NPK, respectively. However, optimal treatment had a 4% yield advantage over tithonia. Within Ultisols, tithonia gave higher yields compared to N, NP, NPK, and optimal fertilizer in the tune of 36%, 18%, 7%, and 7%, respectively. This study concludes that use of tithonia not only enhances productivity on acidic soils, but also has a higher cost benefit compared to commercial fertilizers. However, there is need to devise methods of biomass accumulation and safe storage to enable farmers access sufficient amounts for application at sowing time.