Organic matter and nitrogen conservation in manure compost for organic agriculture

Compost is a main source of organic matter (OM) and of nitrogen for organic farming in and and semiarid regions. An effort has been made to reduce nitrogen loss during composting of separated cow manure (SCM) using high C/N additives - wheat straw, (WS), grape marc (GM) and slightly acidic additive such as orange peels (OP). The resulting composts contained 2.63%, 2.84% and 2.39% N for the GM-SCM, OP-SCM and WS-SCM, respectively. Values of N loss from the raw mixtures were 18%, 5% and 2% for the three compost types, respectively. OM values were 70%, 57% and 53% for the three compost types, respectively. Nutritional contribution of the composts was assessed using cherry tomato as a test plant, growing in the composts as growing media. Peat moss served as a control medium. The media were either unfertilized or fertilized with guano. Plant responses suggest that growth is mainly affected by nitrogen availability while flower production and fruit set is also affected by potassium availability. It was found that fertilization was not necessary for at least 2 months after planting for OP-SCM and WS-SCM.