Abstract
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.
Highlights
The economic growth and life quality index in the semiarid environment of northeast Nigeria largely depends on the agricultural sector, which accounts for over 25% of the gross domestic product (Nandwa, 2003)
The major cause of soil fertility depletion is the imbalance caused by nutrients which are not commonly replaced when removed; resulting innegative nutrient balances (Gichuru et al, 2003)
According to Sanchez et al (1997), in the past 30 years, nutrient depletion was estimated at an average of 660 kg N/ha, 75 kg P/ha and 450 kg K/ha from about 200 million hectares of cultivated lands in 37 African counties (Nigeria inclusive)
Summary
The economic growth and life quality index in the semiarid environment of northeast Nigeria largely depends on the agricultural sector, which accounts for over 25% of the gross domestic product (Nandwa, 2003). According to Sanchez et al (1997), in the past 30 years, nutrient depletion was estimated at an average of 660 kg N/ha, 75 kg P/ha and 450 kg K/ha from about 200 million hectares of cultivated lands in 37 African counties (Nigeria inclusive). This net negative nutrient balances for African soils appear to be a contributing factor in nutrient impoverishment, reduction of agricultural productivity and the stagnation or decline in national economies. Cultivated land in temperate regions, on the average, receives nutrients in excess of those removed in
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