Response of Maize to Organic and Inorganic Sources of Nutrients in Acid Soils of Kenya

aize yield in Kericho County, Kenya is limited by infertile acidic soils. The effect of inorganic sources of nutrients and amendments; triple superphosphate (TSP), calcium ammonium nitrate (CAN) and lime, were compared to a range of organic nutrient sources; Farmyard manure (FYM) of low and high quality, dried cow dung, goat manure, tithonia applied as green manure or dried, in a greenhouse and field experiment. Two soils collected from two farmers’ fields in Sigowet and Litein locations (Hereafter referred to as Sigowet and Litein) were used in the greenhouse where maize was grown for six weeks and its biomass yield determined. The treatments that showed promise were used in a subsequent field experiment where maize was grown to maturity and grain yield determined. In the greenhouse, maize responded to application of all the sources of nutrients and amendments, except lime when applied without TSP, on Sigowet’s soil. On Litein’s soil, maize did not respond to application of lime alone or with TSP, TSP and dried tithonia. High quality FYM gave the highest increase (136%) in dry matter yields on Litein’s soil. In the field experiment, goat manure gave the highest grain yield. Maize failed to significantly respond to either CAN or TSP when applied alone but the application of the two in combination (TSP + CAN) effected a significant response indicating that both N and P were deficient in this soil. All the manures, except low quality FYM, gave yields that were higher or comparable to the standard recommended fertilizer practice (TSP + CAN) and could be economically attractive substitutes as they are locally available. There was a poor correlation between dry matter biomass yield in the greenhouse and grain yield in the field. Extrapolation of greenhouse findings to different fields should therefore be treated with caution

Evaluation of crop arrangement and phosphorus rate on performance of maize-common bean intercropping in western Kenya

The effect of phosphorus (P) rate and crop arrangement on the performance of component crops in maize-bean intercropping systems was investigated at two sites; Malanga and Bugeng’i in western Kenya. A split plot design with five crop arrangements in the main plots i.e., one row of maize alternating with one row of beans (conventional), maize and beans planted in the same hole, two rows of maize alternating with two of beans (Mbili), sole maize and sole beans, in a factorial combination with three P rates; 0, 30, and 60 kg ha-1 in the subplots, was used. Bean yields were low (< 1 t ha-1) but they increased with increasing P rate at both sites. Response of maize to P fertilizer was however poor at Malanga mainly due to Striga weed infestation. Yields of beans did not significantly differ among crop arrangements at both sites. At Bungeng’i, there was a significant interaction between P rate and crop arrangement. At this site, the maize yield in the conventional arrangement increased with increasing P rate but for the Mbili arrangement, the grain yield from application of 30 kg P ha-1 was significantly higher than that at 0 kg P ha-1 and similar to that 60 kg P ha-1. Therefore, it is not beneficial to fertilize beyond 30 kg P ha-1 at this site with the Mbili arrangement. Intercropping was beneficial in all crop arrangements (Land equivalent ratio >1) and can therefore be practiced, except for maize and beans planted in the same hole with no P application at Bugeng’i

Effect of organic and inorganic phosphorus sources on maize yields in an acid soil in western Kenya

Maize production in western Kenya is commonly limited by P deficiencies and aluminum phytotoxicity. Due to high costs of imported fertilizers and lime, focus is now shifting to solutions that utilize local resources. We tested the effect of three inorganic P sources i.e., triple superphosphate (TSP), Minjingu phosphate rock (MPR) and Busumbu phosphate rock (BPR), each applied in combination with two organic materials (OMs) i.e., farmyard manure (FYM) and Tithonia diversifolia green manure (tithonia), or with urea on soil chemical properties related to soil acidity, P availability and maize yields for three consecutive seasons in western Kenya. The OMs and inorganic P sources were applied to provide 20 and 40 kg P ha-1 respectively in their combination. Where urea was used, the inorganic P sources were applied at 60 kg P ha-1. Maize did not respond to application of TSP, MPR or BPR with urea in the first two seasons. However, after three seasons, maize significantly responded to application of MPR with urea. FYM was more effective than tithonia in increasing the labile inorganic P pools but it gave lower maize yields than tithonia which was more effective in reducing the exchangeable Al. It appears that the ability of an OM to lower the exchangeable Al is more important inincreasing maize yields than its ability to increase P availability. The effectiveness of the inorganic P sources in increasing maize yields followed the order of their effectiveness in increasing available P, i.e., TSP[MPR [BPR, once Al phytotoxicity was reduced by application of tithonia but the difference between TSP and MPR was not significant. The extra maize yield obtained by the additional 40 kg P ha-1 from the inorganic P sources was, however, in most cases not substantial enough to justify their use. Economic considerations may therefore favour the use of tithonia or FYM when applied alone at 20 kg P ha-1 than when combined with any of the inorganic P sources used in this study at a total P rate of 60 kg ha-1

Micro-Dosing of Lime, Phosphorus and Nitrogen Fertilizers Effect on Maize Performance on an Acid Soil in Kenya

High cost of inorganic fertilizers and lime has precluded their use by smallholder farmers to remedy the problem of soil acidity and infertility in Kenya. To address the problem, we tested a precision technique referred to as micro-dosing, which involves application of small, affordable quantities of inorganic inputs on an acid soil in Busia County, Kenya. Experimental treatments were N-fertilizer (0 and 37.5 kg N ha-1), P-fertilizer (0 and 13 kg P ha-1) and lime (0, 0.77 and 1.55 tons lime ha-1). 37.5 kg N and 13 kg P ha-1 are 50% of the recommended fertilizer rates for maize production in Kenya while 0.77 and 1.55 tons lime ha-1 are 25 and 50% of the actual requirement. Soil chemical changes, maize grain yield and nutrient recovery were determined. Lime and P-fertilizer significantly affected only the top-soil pH, Ca, Mg and available P, while the effects of N-fertilizer were evident on both top- and sub-soil N likely due to its faster mobility than P and lime. Grain P-fertilizer recovery efficiencies were 14 and 16-27% due to 13 kg P and 13 kg P + 0.77-1.55 tons lime ha-1, respectively. N-fertilizer recovery efficiencies were 37 and 42-45% due to 37.5 kg N and 37.5 kg N + 0.77-1.55 tons lime ha-1, respectively. Fertilizers applied to supply 37.5 kg N, 13 kg P and 0.77-1.55 tons lime ha-1 increased grain yield above the control by 134, 39 and 12-22%, respectively, therefore micro-dosing of these inputs can increase maize production on Kenyan acid soils

Phosphorus Sorption and Lime Requirements of Maize Growing Acid Soils of Kenya

In Kenya, maize (Zea mays L.) is mainly grown on acid soils in high rainfall areas. These soils are known for low available phosphorus (P), partly due to its sorption by aluminium (Al) and iron oxides. The study determined soil P sorption, lime requirements and the effects of lime on soil pH, Al levels and available P on the main maize growing acids soils in the highlands east and west of Rift Valley (RV), Kenya. Burnt lime containing 21% calcium oxide was used. The soils were strongly to extremely acid (pH 4.85-4.07), had high exchangeable Al3+ (> 2 cmol Al kg-1) and Al saturation (> 20% Al), which most maize germplasm grown in Kenya are sensitive to. The base cations, cation exchange capacity and available P (< 10 mg P kg-1 bicarbonate extractable P) were low, except at one site in the highlands east of RV indicative with history of high fertilizer applications. Highlands east of RV soils had higher P sorption (343-402 mg P kg-1) than the west (107-258 mg P kg-1), probably because of their high Al3+ ions and also the energies of bonding between the soil colloids and phosphate ions. Highlands east of RV also had higher lime requirements (11.4-21.9 tons lime ha-1) than the west (5.3-9.8 tons lime ha-1). Due to differences in soil acidity, Al levels and P sorption capacities within and between highlands east and west of RV, blanket P fertilizer and lime recommendations may not serve all soils equally well. Keywords: acid soils, phosphorus sorption, lime requirement

Effects of lime, phosphorus and rhizobia on Sesbania sesban performance in a Western Kenyan acid soil

Aluminium (Al) toxicity, phosphorus (P) deficiency and low rhizobia populations limit Sesbania (Sesbania sesban) performance in tropical acid soils. The study determined the i) indigenous rhizobia populations that nodulate sesbania and ii) effects of lime (0 and 4 t/ha), P-fertilizer (0 and 60 kg/ha) and acid tolerant rhizobia (0 and inoculation) on soil and selected sesbania accessions performance in Western Kenya acid soil. Study site had acid soil, low available P, nitrogen (N) and rhizobia populations that nodulate Sesbania (146 cells/g soil). Lime increased soil pH, while both lime and P-fertilizer increased available P. Aluminium toxicity tolerant and P-efficient accessions (SSBSA004, SSUG3, SSUG4 and SSUG5) had faster growth, higher nodulation, shoot P, and shoot N and response to treatments than the sensitive one (SSBSA203). After 7 months of growth, SSUG3 had highest shoot length (306 cm) and dry matter (5.64 tons/ha), hence, most suitable for building poles and fuel wood. SSUG5 accumulated the highest shoot N (222 kg N/ha) and was therefore, most suitable soil N replenishment. Thus, in acid P deficient and low rhizobial population soils of Western Kenya, the use of lime, P-fertilizer, rhizobia inoculation and Al toxicity tolerant Sesbania are important for Sesbania establishment and growth. Key words: Rhizobia, Sesbania, soil acidity, aluminum toxicity, lime, phosphorus