Abstract
A field experiment was conducted as an on-farm trial at Uyinmwendin (Rhodic Paleudult), Edo State, Nigeria, in 2009 and 2010 to investigate the residue of compost manure, compost manure + NPK and NPK fertilizer treatments on nutrient concentration and uptake of Abelmuscus esculentus and soil chemical properties. Five treatments were selected viz: untreated (control), compost manure applied at the rate of 20 and 40 t ha-1, NPK applied at the rate of 200 kg ha-1 and compost manure + NPK (that is, complementary use of compost manure applied at 20 t ha-1 and NPK applied at 100 kg ha-1) using randomized complete block design and replicated three times. Analysis of the soil indicated that the soil is acidic, with low nutrient status. Application of fertilizer influenced the soil nutrient status positively. Optimum fruit yield was obtained at 40 t ha-1 compost (49.13 t ha-i). Residually, the N, P and K concentration of okra were significantly higher in compost manure applied at both 20 (2.52% N, 0.43% P and 2.38% K) and 40 t ha-1 (2.09% N, 0.41% P and 2.18% K) and compost manure (2.13 % N, 0.43% P and 1.18% K) than NPK (1.22% N, 0.13% P and 0.62% K) and control (0.73% N, 0.11% P and 0.28% K). Compost manure used solely and in complementary quantity with NPK had higher nutrient uptakes than sole NPK use. The soil N, P and K concentrations were reduced by cropping. They were lowest in untreated control and increased with fertilizer application. The compost manure and compost manure + NPK showed a greater potential for increasing plant macronutrients (N, P, K, Ca and Mg) contents. The increases in the soil N, P and K contents after cropping associated with compost manure + NPK treated plots is an indication that compost manure + NPK treatment is a better alternative to inorganic fertilizers because it can sustain continuous cropping. Key words: Nutrient content and uptake, soil amendments, soil chemical properties.
Highlights
Okra production in Nigeria is predominantly carried out by the resource-poor farmers
Five treatments were involved viz: untreated, compost manure applied at 20 and 40 t ha1, NPK applied at the rate of 200 (30 kg N + 13.58 kg P + 24.90 kg K), kg NPK ha-1 and compost manure + NPK and NPK at 100 (15 kg + 6.79 kg P + 12.45 kg K) kg ha-1
The compost manure was enriched with nutrients
Summary
Okra production in Nigeria is predominantly carried out by the resource-poor farmers. The stability of production depends on replenishing nutrients removed from the soil by crops, maintaining desirable physical condition of the soil, preventing an increase in soil acidity and toxic elements and minimizing or preventing erosion (Sanwal et al, 2007). This emphasizes the importance of fertility restoration in achieving and maintaining high crop productivity and it can be achieved through the use of external fertilizer input. Other problems associated with the use of inorganic fertilizers include pollution of ground water after harvest, non-improvement of soil structure (Gordon et al, 1993); increased soil acidity, reduced crop yield, nutrient imbalance and depletion of organic matter. The problems associated with the use of inorganic fertilizers have diverted the attention of agronomists toward making use of organic materials (both organic manures and organic wastes) for improving the soil physical properties that allow profitable crop production (Somani and Totawat, 1996)
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