Nutrient mineralization from deoiled neem seed in a Savanna soil from Nigeria

• Published in: Communications in soil science and plant analysis Vol. 39; no. 3-4; pp. 524 - 537
• Main Authors: Agbenin, J.O, Ibitoye, S.O, Agbaji, A.S
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA Taylor & Francis Group 01-02-2008; Taylor & Francis
• Subjects: Agronomy. Soil science and plant productions; ammonium nitrogen; application rate; Azadirachta indica; Biological and medical sciences; cation exchange capacity; electrical conductivity; exchangeable cations; fertilizers; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; magnesium; mineralization; neem kernel meal; Neem seed cake; nitrate nitrogen; nutrients; potassium; savanna soil; savanna soils; soil amendments; soil fertility; soil organic carbon; soil pH; Soil science; Soil-plant relationships. Soil fertility; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Nigeria; West Africa; Sub-Saharan Africa; Africa; Savannah; Soil fertility; Tropical zone; Pesticide crop; Meliaceae; Medicinal plant; Neem seed cake; nutrients; Soils; Mineralization; Dicotyledones; Angiospermae; Deoiling; Nutrient; Hardwood forest tree; Spermatophyta; savanna soil; Azadirachta indica
• ISSN: 0010-3624; 1532-2416
• DOI: 10.1080/00103620701826761

The mineralization of nutrients from deoiled neem seed (neem seed cake), the residue left after oil extraction, was examined in a typical savanna soil with a view to determining its potential for fertility improvement. The neem seed cake (NSC) application rates were 0, 2.5, and 5.0 g kg
−1
soil (0, 5, and 10 tons ha
−1
). The concentrations of ammonium-nitrogen (NH
4
-N) and nitrate (NO
3
)-N mineralized from the neem-amended soil were two to three times greater than the control. Similarly, exchangeable potassium (K), magnesium (Mg), and cation exchange capacity were significantly greater than the control. The neem-amended soil maintained organic carbon (OC) at the pre-incubation level, whereas OC in the control soil declined to significantly less than the pre-incubation concentration. The electrolytic conductivity of the soil saturation extract with neem application was 8-10 times greater than the control soil. However, the NSC increased exchange acidity markedly and decreased the soil pH significantly. Thus, the benefits of NSC in increasing the concentrations of N, K, and Mg and maintaining OC of the soil must be weighed against the consequences of soil acidity, though it is unlikely that NSC can acidify the soil to the same extent under field conditions as it did in this closed-system incubation study.