Use of Composted Societal Organic Wastes for Sustainable Crop Production

Composted organic wastes are increasingly pointed out as alternative to chemical fertilisers for crop production. This paper reports on a trial using sewage sludge compost and municipal solid waste compost at two rates (50 or 100 ton/ha) and two systems of application (incorporation to soil or as surface mulch) for the production of wheat (Triticum aestivum) in two consecutive growing seasons: spring (var. Canon) and winter (var. Mercia). Additional treatments were: Nitram (ammonium nitrate, 34.5% N) at 75 or 150 kg of N/ha and a null control. The different treatments were applied in a single dose, in the first season; the objective being the observation of possible residual effects in the second year. There was no statistical difference between the two compost, regarding release of nutrients to soil, biomass production, grain yield and grain quality. Composted societal wastes showed to be able to sustain crop production at levels of quantity and quality similar to those obtained from chemical fertiliser (Nitram, ammonium nitrate, 34.5% N). Results for rates of mineral nutrients at soil level throughout the experiment allow us to conclude that composted societal organic wastes provide nutrients to plants in a balanced way, providing high yields with low risks of soil and underground water pollution. Results for these trials indicate that the residual benefits from compost use for consecutive crops are minimal and, thus, compost should be used as a long term strategy for improving soil fertility, with applications of low doses –up to 50 ton/ha– prior to drilling of each crop or as surface mulch after that.