Spent pig litter as fertilizer for growing vegetables

Spent pig litter disposed of from pig pens employing the pig-on-litter system contained high concentrations of organic carbon and nutrients and served as a source of nutrients for plant production. The 'aged' spent litter (disposed of after 11 months of utilization) had higher nutrients, conductivity, Cu and Zn values than those of the 'young' samples (disposed of after 3 months of use). Amendment of sandy soils with both types of spent litter significantly enhanced the growth and production of a leafy vegetable, Brassica parachinensis. The concentrations of N, P and K accumulated in edible tissues and the plant yield depended on the type of the spent litter and its application rates. 'Aged' spent litter with application rates of 20-30% v/v gave the maximum plant yield, and the plant production was comparable to that with a commercial fertilizer. The tissue nutrient concentrations were also higher than with the 'young' spent litter, implying that more nutrients were available from the 'aged' spent litter than the 'young' one. Although spent litter had high contents of salts, Cu and Zn, the plant growth was not interfered with and the amounts of Cu and Zn accumulated in the edible tissues were not in excess, indicating that heavy-metal contamination was not a serious problem when the spent litter was recycled on to agricultural land.