Field and laboratory incubation studies were conducted to determine the effect of different acid soil management practices; liming (L), combined N and P fertilizers (NP), and goat manure (M) application, for maize production on the dynamics of mineral N, microbial biomass nitrogen (MBN) and microbial biomass carbon (MBC). A randomised complete block design with a 2 3 factorial arrangement replicated thrice was used. The factors, each at two levels, were: NP fertilizers applied as triple superphosphate (0 and 75 kg ha -1 ), and urea (0 and 50 kg ha -1 ), L (0 and 2.5 t ha -1 ) and M (0 and 5 t ha -1 ) giving a total of eight treatments; L, M, NP, LM, LNP, MNP, LMNP and C (control). Soil samples for determination of mineral N, MBC and MBN were collected from the 0-15 and 15-30 cm depths at seedling, tasselling, and maturity stages of maize growth and after 0, 15, 30, 60, 120 and 240 days of laboratory incubation of soils obtained from the same field.The NP treatment had significantly (P< 0.5) higher levels of mineral N in both depths at all stages of maize growth, followed by MNP and LMNP. The net mineralized N (μgN/g dry soil) for the incubated soil followed the order LMNP, MNP, LM, M, L, LNP, C and NP for the two depths. The MNP, LMNP and M treatments had significantly higher MBC and MBN for both field and incubated soils. The correlations between mineral N and MBN were positive but non-significant at seedling and maturity stages of maize growth in the 0-15 cm depth and at seedling and tasselling stages in the 15-30 cm depth. The correlations between MBN and Mineral N for both depths and sampling periods were positive and significant for the incubated soils, The maize grain yield increases (%) above control were 43, 36.4, 31.1, 25.3, 21.9, 13.7 and 3.0 for LMNP, MNP, NP, M, LNP, LM and L treatments, respectively.Application of LMNP and MNP treatments enhanced mineral N, MBC and MBN and concomitantly soil quality and productivity as gauged from the improved maize yields in the respective treatments. Combining manure, lime and chemical fertilizers and /or manure and chemical fertilizers is thus a promising alternative to developing a more sustainable acid soil management strategy for increased maize production in Molo district, Kenya.

Exudation of high amounts of citrate in white lupin (Lupinus albus L. cv. Amiga) has the advantage of being effective in mobilization of a wide range of sparingly soluble P sources. To improve cultivation system of maize, a field experiment was conducted to assess effectiveness of white lupin (Lupinus albus L. cv. Amiga) in increasing solubility of minjingu phosphate rock (MPR), phosphorus balances and maize yields in Njoro sub-County, Kenya. The randomized complete block design experiment was conducted for four seasons; short (October -February) and long rain seasons

Background Low soil fertility and reduced seasonal rainfall contribute to low potato (Solanum tuberosum L.) yield in Kenya. Nitrogen (N) deficiency is the major problem facing by the smallholder farmers of Kenya due to lack of fallow. Hence an introduction of supplemental irrigation with an adequate application of this nutrient could increase potato yield. The objective of this study was to determine the effects of supplemental irrigation and N-fertilisation on potato tuber yield, water use efficiency (WUE) and nitrogen use efficiency (NUE). The experiment was conducted in Nakuru County, Kenya for two seasons. The experimental soils are classified as mollic Andosols. The treatments comprised two irrigation treatments of full supplemental irrigation (FI) and rainfed production (RF) and four N levels of four N levels of 0 (N0), 60 (N1), 90 (N2) and 130 kg N/ha (N3). Results The results showed that total tuber yield, marketable tuber yield and NUE were significantly (P < 0.001) affected by irrigation × N-fertilisation while WUE was only affected (P < 0.001) by N-fertilisation. The highest total tuber yield, 58.28 tonnes/hectare (t/ha), was recorded under FI combined with N3. Treatment FI significantly increased marketable tuber yield by approximately 125.58% in all N treatments compared to RF. The highest NUE of potato (236.44 kg/kg of N) was obtained under FI combined with N3 but not significantly different from the NUE of potato obtained under FI with N2. N-fertilisation N3 produced the highest WUE of 14.24 kg/m3. Significant correlation was obtained between tuber yield and number of tubers/plant (r = 0.75, P < 0.001), NUE (r = 0.95, P < 0.001) and WUE (r = 0.72, P < 0.001). Conclusion High potato yield and marketable tuber yield can be achieved in mollic Andosols when water deficits of the growing season are eliminated with supplemental irrigation and an application of 130 kg N/ha.

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Nitrogen (N) is the most critical plant nutrient. Maize has a high nitrogen demand. Low maize (Zea mays L.), yields in smallholder farms of Malawi, the country’s staple, is attributable to declining N fertility aggravated by the ever increasing price of fertilizer. Little effort has been made to establish the best nitrogen rate in a maize- cowpea and maize-bean intercrop under variable soil conditions as a way of improving production, and was the objective of the current study. Field experiments were conducted at Chitedze Agricultural Research Station in Lilongwe and Makoka Agricultural Research Station in Zomba during the 2016/17 growing season. A split plot layout in a randomized complete block design, with three replicates was used. The main plots were; sole maize, sole bean, sole cowpea, bean/maize and cowpea/maize intercrop systems. The sub plots were N fertilizer rates (0, 52.5, 78.75 and 105 kg N ha-1), applied as urea. The data collected was subjected to analysis of variance using SAS software version 9.3 (SAS Institute Inc.) at P<0.05. Means were separated using Duncan Multiple Range (DMRT) test at 95% significance level. The results showed that application of N increased maize N uptake and grain yield. NUE however decreased with increasing N fertilizer rate.