A study was conducted on nutrient dynamics through partial N, P and K balances during 2005 growing season. The treatments involved three levels of farmyard manure (FYM: 2.5, 5.0 and 7.5 tons/ha) combined with half (N30P15K15 kg/ha) and full (N60P30K30 kg/ha) recommended rates of NPK fertilizer and sole recommended rates of FYM (7.5 tons/ha) and NPK (N60P30K30 kg/ha) and a control. The experiment was laid out in RCB design with three replicates. Data on nutrient inputs (fertilizers and FYM) and outputs (grains and crop residues) were estimated using the budgeted method. The treatment means were statistically compared using Duncan multiple range test (DMRT). The lowest N-balance (-44.70 kg/ha/year) resulted from combination of lowest levels of FYM and NPK, and increased with increasing rates. Sole 7.5 t of FYM resulted in positive N-balance (19.00 kg/ha/year) compared to sole recommended rate of NPK (-2.40 kg/ha/year). P balance varied from as low as -1.54 kg/ha/year in control to as high as +36.16 kg/ha/year in plots which received 7.5t FYM + N60P30K30 kg/ha. All the treatments had negative K-balances ranging from -6.60 kg/ha/year in plots applied with 7.5t FYM/ha to -108.89 kg/ha/year in plots which received 2.5 t FYM/ha + N60P30K30 kg/ha, depicting high plant K-uptake relative to inputs. The grain yields varied from 789 kg/ha in control to 2440 and 2301 kg/ha in plots applied with 7.5 t FYM/ha + N60P30K30 kg/ha and 7.5t FYM/ha + N30P15K15 kg/ha, respectively. Combination of sub-optimal rates of FYM and NPK fertilizers enhanced millet yields with positive N and P balances in the soils.
Key words: Sole millet, sandy loam soil, nutrient balance, northeast Nigeria.
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