Keywords: agro–industrial waste, residual effect, soil fertility, maize nutrition, organic matter, crop yield, heavy metals, soil quality
Residual effect of agro–industrial wastes on soil properties and Zea mays (L.) nutrition
The residual effect of agro–industrial wastes previously used for potato growing was investigated for soil characteristics and maize nutrition. The soil pH increased and organic matter decreased during maize growth. Nitrogen and K were generally low, but statistically higher almost in waste–applied soils. Soil phosphorus was greatest in the 'Only Wastes' and 'Min.P + Wastes NK' treatments. N, P, K and Ca decreased significantly in the soil of 'Only Wastes' during maize growth, as did the organic matter content. 'Only wastes' generally produced a maximum maize growth parameter. Zinc and Mn were low in soils and no pollution risk arose with respect to heavy metals. Nitrogen, K, Zn and Mn of leaves were below adequate levels. Lead and Cr in plants decreased with the chelating effect of increased organic matter. Phosphorus in wastes gave significantly the highest yield, and P in kernel had the effect of increasing some yield parameters in maize.