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The aim of the study was to examine the effect of combined use of organic residue with inorganic fertiliser-P on organic residue decomposition, P transformations and utilisation by upland rice. Five agroforestry tree prunings (organic residues) were incubated without and with inorganic fertiliser-P for 56 days using soil as inoculum only. Decomposition and P release were in the same order i.e. Gliricidia sepium > Senna siamea > Leucaena leucocephela > Paraserienthus falcataria > Acacia mangium. The lignin, polyphenol and cellulose contents and their ratios to the P content of the residue influenced decomposition and hence P release. Added inorganic fertiUser-P had no effect on decomposition. A greater proportion of inorganic fertiliser-P was recovered when applied with low quality residue and less with high quality residue. Gliricidia sepium and Acacia mangium prunings were incubated without and with morganic fertiliser-P for 56 days in high and low P status soils. Gross mineralisation was estimated by isotopic dilution. Unlike Acacia, Gliricidia increased gross mineralisation in the low P status soil with weaker P sorbing capacity although net mineralisation was not attained. Inorganic fertiliser-P had no effect on gross mineralisation. Organic residue influenced both the inorganic and organic labile soil P fractions while inorganic fertiliser-P influenced only the labile inorganic P fractions. Upland rice (ROK 16) grown on the two soil types treated without and with Gliricidia and inorganic fertiliser-P indicated increased dry shoot weight and total P uptake in the low P soil and not the high P soil. With a double isotopic labelling technique, it was observed that in the low P status soil, Gliricidia P-accounted for over 50% of the total rice P uptake followed by organic-P (25%). Over 80% of the total P uptake in the high P status soil was soil-P. Organic residue increased the quantity of inorganic fertiliser-P utilised but not the native soil P.

MSCAGR / Department of Plant Production / Chickpea (Cicer aritienum L.) is an ancient crop that originated in South-Eastern Turkey and belongs to the genus Cicer, tribe Cicereae, and family Fabaceae. Chickpea has the ability to fix atmospheric nitrogen (N) for its growth. However, chickpea productivity not only depends on N2 fixation or dry matter accumulation, but also the effectiveness of nutrient partitioning to seed, a key component to overall yield. There is a dearth of information on the effect of P with rhizobial inoculation in response of nutrients accumulation in the rhizosphere, shoots and grain of chickpea, especially when determined at different growth stages in the African continent. This study contributes knowledge on this crucial aspect which will likely lead to more other similar research reports in other settings. Therefore, the objectives of this study was to evaluate the effect of P fertilizer rates and rhizobial inoculation on yield and nutrients accumulation in two chickpea genotypes. Field experiments were conducted in winter 2017 and 2018 at University of Venda, Thohoyandou and University of Limpopo’s experiment farm, Syferkuil. Treatments consisted of a factorial combination of two rates of P fertilizer (0 and 90 kg P ha-1), two desi chickpea genotypes (ACC1 and ACC5) and two rhizobial inoculation levels (with and without rhizobiam strain). The treatments were laid out in a randomized complete block design (RCBD) and replicated three times on 22 April 2017 and 11 April 2018 (Syferkuil), 13 April 2017 and 29 April 2018 (Thohoyandou). Macronutrients including P, K, Ca, Mg were determined using the citric acid method. The total N concentration were determined by the micro-Kjeldahl method in both soil, shoots and grain. Zn was extracted using a di-ammonium ethylenediaminetetraacetic acid (EDTA) solution. The content of macronutrients (P, K, Ca, Mg, Ca, and Zn) in soil, shoots and grain was determined by first subjected to wet digestion (Mehlich, 1984). From the digest, various elements were read using relevant procedures. P contents was determined colorimetrically using a spectrophotometer. Yield and yield components were assessed at harvest maturity. Genotypes affected the accumulation of mineral elements in rhizosphere soil, shoots, grain and yield. Accession 5 performed better in most of nutrients elements compared to accession 1 in both seasons and sites. Application of phosphorus alone, and in combination with rhizobium inoculation increased the concentration of majority of nutrients in the rhizosphere. When the test accessions were grown at the Syferkuil and Thohoyandou study location in 2017, they showed significant differences in the concentration of N, P and K while Ca, Mg and Zn were similar in the rhizosphere. The concentrations of N, P and K were markedly higher in the rhizosphere of ACC5 compared to ACC1. In fact, the concentration of P was two-fold greater in the rhizosphere of ACC5 than ACC1. Accession 5 exhibited a markedly higher shoot dry weight, number and dry weight of pods, 100-seed weight, grain yield and harvest index compared to ACC1. P plus rhizobium inoculation, P, rhizobium inoculation affected grain yield and yield components of chickpea genotypes. This preliminary finding show that the combination of P and rhizobium inoculation affected the nutrients accumulation in the rhizosphere, shoots, grain, yield and yield components in both locations. Moreover, Thohoyandou had the highest nutrients accumulation on the rhizosphere, shoots, grain, yield and yield components compared to Syferkuil. / NRF