Nhunda, Daniel Masumbuko2024-06-032024-06-032023https://www.suaire.sua.ac.tz/handle/123456789/6207MSc. Dissertation in Soil Science and Land ManagementTo optimize production of maize and other crops, assessment of soil fertility should be done in agricultural areas from which cite specific fertilizer recommendations will be established. This study was conducted in selected fields of Kongwa district in Dodoma Region to assess the soil fertility status and maximize availability of Phosphate from Minjingu phosphate rock (MPR) for maize production through the use of phosphate solubilizing bacteria (PSB). The specific objectives of the study were to determine the levels of N, P, K, S, Mg, Ca, Na, Zn, Cu, Fe and Mn in soils and evaluate capability of phosphate solubilizing bacteria (PSB) on enhancing P availability from Minjingu Phosphate Rock (MPR) and evaluate field characteristics in slightly acid to neutral soils. Assessment of soil fertility status was done by analysing soils from twenty-four maize growing areas of Kongwa district. Composite soil samples of top soils (0 – 20 cm depth) were collected for physical and chemical analysis. Organic carbon was determined by the Walkley-and Black wet oxidation method (Nelson and Sommers, 1982) and total nitrogen (TN) by the micro-Kjeldahl procedure (Loria et al., 2005). Available P was extracted using Bray-1 and Olsen methods of Bray and Kurtz (1945) and measured by Spectrophotometer following colour developed by molybdenum blue method (Murphy and Riley, 1962). Exchangeable bases were extracted by ammonium acetate saturation method (Thomas, 1986) and cation exchange capacity was determined from NH 4+ saturated soil colloids and displaced using 1 M KCl, then determined by Kjeldahl distillation method for estimation of cation exchange capacity (CEC) of the soil (Robertson and Philip et al., 1999). Extractable sulphur (SO4 2- S) was extracted using calcium monophosphate (Ca(H 2 PO 4 ) 2 .H 2 O), then determined by the turbidimetric method as described by Moberg (2001). The EC for soil samples from Kongwa was measured by using EC meter in a 1:2.5 soil: water (or CaCl 2 for pH only) extract as described by McLean, (1982).Extractable metallic micronutrients e.g., Cu, Fe, Zn and Mn, were extracted by diethylenetriaminepentaacetic acid (DTPA) as described by Lindsay and Norvell (1978). Results indicated that 48% of the sampled fields were sandy clay loam, 26% were sandy loam and the remaining whad a clay or loamy sand textural classes. Soil pH ranged from extremely acid (3.52) to moderately alkaline (7.7), organic carbon ranged from very low to medium (0.19-1.60%) and total N values were very low to low (0.01-015%). Also, results indicated 42% of soils had P deficiency and 16.7% with inadequate S. In addition, 45.8% of the soils had inadequate exchangeable K and exchangeable Mg were very low to high (0.29-4.06cmol (+) kg -1 ). Exchangeable Ca was low to very high (1.06 to 10.04 cmol (+) kg -1 ) with favourable base saturation for crop production. The CEC ranged from very low (2.62cmol (+) kg -1 ) to medium (18.9 cmol (+) kg -1 ). Extractable micronutrients such as Cu, Fe, and Mn were adequate but Zn was inadequate in 58% of the soils. The study area had poor soil fertility is poor with deficiencies in N, P, K, Zn, Mg, and Ca, hence calling for proper management to improve crop production. Phosphorus (P) is one of the major growth-limiting macronutrients required for proper plant growth and it is contained within nucleic acids, enzymes, coenzymes, nucleotides, and phospholipids. One of the ways to replenish P in soils is the use of inorganic fertilizers such as Minjingu Phosphate rock. The challenge is that, phosphate rock (PR) generally requires P-deficient acidic soils with pH of less than 6.2 for P to be released and become available for uptake. Application of PR in neutral to slightly alkaline to soils (pH >6.2) is therefore discouraged since PR solubility is very low in such soils and therefore can not supply sufficient available P to plants. Phosphate solubilizing bacteria have a capability among others, of producing organic acids which in turn lowers the local acidity of the soil in which they operate. The lowering of the pH will/may bring about right conditions for solubility of MPR . Maize trials were established in two villages (Nghumbu and Mlali) of Kongwa District to assess effectiveness of PSB in solubilizing MPR in neutral to slightly alkaline soils and two factors were tested, which are field characteristics (in which treatments were sites), the second factor was PSB co-applied with MPR. Maize trials were established using randomized complete block design (RCBD), the seven sites ,PSB inoculum co-applied with different rates of Minjingu phosphate rock (MPR) (0 – 60 kg ha -1 ). Limiting nutrients such as N and S were corrected then Minjingu RP was applied as basal fertilizer during planting by placing it below the seed and covering with a thin layer of soil followed by a co-culture of PSB inoculant at 5 mL (10 9 bacteria per litre) poured around each plant four days after emergence. Maize plants were harvested at maturity then grain and straw samples were analysed for N, P and K content, phosphorus uptake and phosphorus use efficiency were calculated. Using the soil data, it was found that Nitrogen was the main limiting nutrient in all seven fields. The limiting nutrients in Nghumbi were N and K while N, P, K and Zn were limiting nutrients in Mlali village. In the trial fields, the main effect of fields’ characteristics indicated that the performance of maize and its analyzed parameters (N, P, K, S, Mg, Ca, Na, Zn, Cu, Fe and Mn) were significant (P < 0.001) across the fields reflecting heterogeneity in nutrient levels. There was no significant effect of PSB treatments on maize grain yield and straw yield. Results also did not show significant (P =0.427) interaction effects of field characteristics and treatment combinations on the measured variables in maize because of drought experienced in the study area. The findings of the present study, apart from setting site-specific fertilizer recommendations, also suggest that the performance of maize in the study area depends on the soil nutrient status, especially for native P, N, and K. The studied soils need external nutrient inputs and proper management to optimize crop production and more research is recommended on PSB for more than one season in neutral to slightly alkaline soil before ascertaining the technology to farmers because in this season PSB did not enhance solubility of MPR due to drought experienced in the study area.enMaizeSoil fertilityAlkaline soilThesis