Kimaro, Anthony Anderson2026-02-042026-02-042000https://www.suaire.sua.ac.tz/handle/20.500.14820/7289DissertationThis study was carried out at Sokoine University of Agriculture (SUA) Farm, Morogoro, Tanzania to assess the effect of Gliricidia sepiutn green manure (GM) placement method on solubility of Minjingu rock phosphate (MRP), growth and yield of maize. The study involved pot and field factorial experiments with treatments arranged in a complete randomized block design in three replications. For the pot experiment, the experimental factors were G. septum. GM placement method (5 t ha’1) at three levels (i.e. No GM, Incorporation and Mulching) and P- fertilizer application rates at seven levels (i.e. 0, 12.5, 25, 50, 100, 150 mg P kg soil’1 as MRP and 50 mg P as TSP). Air dried soil (2 kg) was filled in each of the 63 pots representing the 21 treatment combinations. The various treatments were then incubated at 70% field capacity (FC) at ambient temperature for three months. Within this period soil sub samples were collected at two weeks intervals for available phosphorus (AVP) deter mination in the laboratory. For the field experiment, the experimental factors remained the same as for the pot experiment except that the P-fertilizer application rates were 0, 10, 20, 40, 80 kg P ha’1 as MRP and 30 kg P ha’1 as TSP. Soil samples were collected at two weeks intervals for the determination of AVP in the laboratory. Additionally, maize height (m) at tasseling stage was recorded and maize samples were collected for the determination of P and N in the leaf, grain and stover. Grain and stover yields were also determined at maturity. The results indicated that GM placement method significantly improved AVP in both pot and field experiments, with the highest AVP obtained by the incorporation treatment. In most of the sampling dates AVP values for incorporation and mulching treatments were not significantly different in both the pot and field experiments. The AVP increased with increase in MRP application rates for both experiments and for all sampling dates. Except for stover N, GM placement method significantly increased concentration and content of P and N in maize leaf. For the incorporation treatment, the values were leaf concentra- tion (0.2005% P; 2.298% N) and leaf content (5.835mg P; 66.19 mg N). The corresponding values for the mulching treatment were leaf concentration (0.1908% P; 2.252% N) and leaf content (5.426 mg P; 63.43 mg N). Similarly, P and N uptake were significantly increased by GM placement method. The uptake values for incorporation treatment were as follows: grain (6.22 kg ha"1 P;37.82 kg ha"1 N), stover (2.18 kg ha"1 P; 10.98kg ha"1). Whereas corresponding values for the mulching treatment were grain (5.40 kg ha"1 P; 33.77 kg ha"1 N), and stover (1.76 kg ha"1 P; 9.59kg ha"1). Total P and N and maize height as affected by GM placement method followed a pattern similar to that of P and N for grain and stover. Maize yield was (2.07 kg ha"1 grain; 2.57 kg ha"1 stover) for control, (2.60 kg ha"1 grain; 3.33 kg ha'1 stover) for incorporation and (2.34 kg ha"1 grain; 2.98 kg ha"1 stover) for mulching. P and N uptake by maize significantly increased with increase in MRP application rate. However, at higher rates (i.e. 40, 80 kg P ha"1 as MRP), the increase of maize leaf P and P uptake was not significant. Generally, most of the parameters studied showed a linear and quadratic relationship with MRP application rates. Furthermore, the interactions between GM placement method and MRP application rates for most of the parameters studied were not significant. Based on the results of this study, it was concluded that incorporation and mulching of GM has the potential to improve solubility as well as growth and yield of maize. However, adoption of the practice may be limited because of the labour required in cutting, transporting and incorporating the GM into the soil. Getting a source that will provide sufficient amount of GM to cater for the needs of most of small holder farmers at the appropriate time may also be a problem. Furthermore, GM in this study was used as a source of N for maize and this is merely transferring nutrients within the farm and not actually redressing the nutrient depletion in the soil, therefore it may not be sustainable in the long run.enGliricidia sepiumGreen manure placementSolubilityMinjingu rock phosphateMaize farmMorogoroTanzaniaArticle