Influence of decaying sweet potato crop residues on nutrient uptake of sweet potato plants

Abstract

Sweet potato cultivar ‘Centennial’ ( Ipomoea batatas (L.) Lam.) indicator plants were grown in either coarse silica sand or silt loam soil amended with either dried peatmoss, cowpea ( Vigna unguiculata (L.) Walp.) shoots, sweet potato vines or sweet potato roots at a rate of 1.67% (w/w). The effects of these plant residues on nutrient concentration and uptake of sweet potato shoots were compared with a non-amended control. Whole shoots were analyzed for P, K, Ca, Mg, S, Na, Fe, Zn, Mn, B, Al and Cu. Shoot dry weights were less for plants grown in either sweet potato vine or root residue, regardless of growing media, suggesting that sweet potato residues have an allelopathic effect. Indicator plants grown in sweet potato crop residues had lower concentrations of Ca, Mg and S. Tissue analysis data expressed as plant content suggested reduced uptake of P, K, Ca, Mg, S, Zn, B and Cu. Significant correlations between plant growth and Ca, Mg and S concentrations in shoots were found. Although growth inhibition could not be associated conclusively with reduced uptake of a particular nutrient, the altered uptake of these three nutrients might affect plant growth in soils which contain decaying sweet potato crop residues.