Inherent low soil nitrogen (N) and phosphorus (P) is one of the major hindrances of increased soybean productivity in Malawian soils. Although, inoculation of legumes with rhizobia, has been advocated for decades as a way of boosting leguminous crops’ productivity through biological nitrogen fixation (BNF), the effectiveness of this strategy, has been low. An experiment was carried out to investigate the effect of the application of small doses of N and P to inoculated soybean. It was laid out in a complete block design (CBD) replicated three times and the treatments included: 1. Soybean only, 2. Inoculated soybean, 3. Inoculated soybean + 30 kg N ha -1 , 4. Inoculated soybean + 30 kg N ha + 25 kg P ha, 5. Inoculated soybean + 30 kg N ha + 35 kg P ha. The soybean in all treatment plots except for treatment 1 was inoculated with 30 kg N ha -1 applied as urea to treatment plots 3, 4 and 5. Phosphorus as TSP was applied to treatment 4 and 5 at the rate of 25 and 35 kg P ha -1 . Data collected included; selected soil physical and chemical properties, Original Research Article Phiri et al.; IJPSS, 10(5): 1-7, 2016; Article no.IJPSS.24905 2 biomass and pod yields. Data obtained were subjected to Analysis of Variance (ANOVA) using the GenStat statistical package and treatment effects tested for significance using the F-test at 5% level of significance. Means were separated using the least significant difference (P<0.05). Results indicate that inoculating soybean with rhizobia and inoculating soybean with rhizobia plus applying 30 kg N ha -1 did not significantly increase biomass yields. However, inoculating soybean plus the combined application of 30 kg N ha and, 25 kg P ha or / and 35 kg P ha increased the soybean biomass yields by 54% and 70% respectively above control. The lack of significant response when N was applied without P points to the significant role played by phosphorus in root development and energy transfer processes within the plant. Effective nodulation, however, was significantly higher (p<0.05) above the control where inoculation was combined with the application of 30 kg N ha and 35 kg P ha, hence underlining the role played by phosphorus in nodule development and the role of starter N in soils low in N.

Acid soils cause soil fertility problems such as Al and Mn toxicity, Ca, Mg, N deficiency and P fixation. These are constraints to high crop yields. Historically, liming is the common management practice used to neutralize soil acidity and to overcome the problems associated with soil acidification. A field experiment was conducted to investigate the effects of cropping systems, lime placement methods and lime rates on some soil chemical properties and nutrient uptake by sugarcane during the plant crop and ratoon one cycle under acidified Cambisols of Kibos, Kisumu, Kenya. A Split - split plot in randomized complete block arrangement was employed. The factors and respective levels (in parenthesis were): main plot; two cropping systems (sugarcane monoculture [MC] and intercropped sugarcane and soybeans [IC]). The sub – plots were three lime placement methods (lime broadcasted [L-BC], lime shallow banded, 0 – 15 cm [L-SB] and lime deep banded, 15 – 30 cm (L-DB] and the sub - sub plots were three lime rates (0, 1 and 2 t ha-1). Lime rate of 2 t ha-1 significantly (P ≤ 0.05) increased soil pH to 6.4 and 5.2 as determined in water and 1 N KCl, respectively compared to 1 t ha-1 and control (0 t ha-1). Increased lime rate led to decreased levels of manganese, iron, and copper hence confirms the inverse relationship between soil pH and these micronutrients. Lime deep banded (L-DB) increased soil pH and available phosphorus for soil depth 15 – 30 cm compared to lime shallow banded (L-SB) and lime broadcasted (L-BC). Intercropped sugarcane and soybeans (IC) led to increased soil acidity and soil organic carbon (SOC) than did sugarcane monoculture (MC). For nutrient content of sugarcane leaves, IC system led to increased Ca and Mn compared to MC. Lime broadcasted (L-BC) caused high nitrogen and phosphorus content of sugarcane leaves and lime shallow banded resulted in increased Ca and Zn content of sugarcane to optimum levels. In view of the findings, the lime rate of 2 t ha-1 is recommended for use to ameliorate soil acidity for acidified Cambisols of Kibos, Kisumu County, Kenya. Lime broadcasted (L-BC) is preferred to ameliorate acidity at top depth (0 – 15 cm) while lime banded both (L-SB) and L-DB) is preferred to reduce sub - soil acidity.

One of the causes for declined sugarcane yields is low soil nutrient levels, especially the most limiting ones, nitrogen (N) and phosphorus (P). This is further aggravated by inadequate or lack of nutrient replenishment. The study conducted at KESREF, Kibos, experimental field on a Eutric Vertisol soil evaluated the effect of four P sources, single superphosphate (SSP), triple superphosphate (TSP), diammonium phosphate (DAP), and rock phosphate (RP), and four P levels (0, 17, 34, and 52 kg P ha–1) on yield and quality of sugarcane varieties KEN 82-808 and CO 421. P sources significantly influenced yield of variety CO 421 at second ratoon harvest, the trend being DAP > RP > TSP > SSP. Effect of P sources on quality was not significant. Application of P increased population of millable stalk and yield compared with the control (0 kg P ha–1) in both KEN 82-808 and CO 421. Highest yield was recorded when P applied was 34 kg P ha–1 and lowest in control (0 kg P ha–1), the trend being 34 > 17 > 52 > 0 kg P ha–1. Effect of P rates on quality was not significant. It is concluded that fertilizer P sources can be applied to supply P. P plays a significant role on yield parameters than on quality parameters. The level 34 kg P ha–1 (80 kg P2O5 ha–1) is appropriate to maintain the crop to second ratoon harvest for increasing the yield.

This study evaluated acid ameliorative potential and their effects on maize growth of four organic residues namely wild spikenard, cordia, cowpea and pigeon peas through incubations with or without sulphur. This was done in order to recommend potential organic residue source that could ameliorate soil acidity associated with sulphur dusting. Increased levels of sulphurin the soils reduced the growth and dry matter yields of maize due to intense acidification while maize growth and dry matter yields in soils which organic residues were incorporated was enhanced. Enhancement in maize performance may be a result of reduced soil acidity due to ameliorative effects of residues which was directly related to the alkalinity of the organicresidues. Pigeon pea and cordia residues, which had higher alkalinity, resulted in a higher acid amelioration compared to senescent cowpea and wild spikenard, which had lower alkalinity. The performance of maize grown in respective soil incorporated with the organic residues followed the same pattern. The finding suggests different acid ameliorating potential of residues, pigeon peas and cordia being the most effective. The residues are therefore recommended in cashew farming system in order to improve soil fertility to enhance crop production.