Abstract
The effects of a sewage sludge compost on the nutritional status and crop performance of cassava (Manihot esculenta, Pl 12095) were evaluated on a Mollisol (Cumulic Haplustolls) and an Ultisol (Aquic Haplohumults) of Puerto Rico. Compost rates evaluated were 0, 33.5, 67,134, and 402 t/ha. At its highest rate, compost additions caused a reduction in yield in Corozal, Moreover, the addition of compost increased the number of non-commercial roots. It is suspected that such effects were due to the highly saline nature of the compost. The nutritional status of the plants was minimally affected by the compost. Significant effects were observed only at the highest treatment: an increase in uptake in the case of nitrogen, phosphorus and potassium, and a decrease in the amount of magnesium and iron uptake. An evaluation of the nutrient distribution among different piant tissues revealed that nitrogen, phosphorus, magnesium, calcium, and zinc were concentrated mostly in the leaves, whereas potassium and iron were concentrated mostly in the root peel. Cadmium was the only element exhibiting equal or higher concentration in the pulp tissue than in the peel. This finding substantiates the potential for cadmium to enter the human food chain and emphasizes the need to monitor the concentration of this element in soils where cassava is to be grown.