Impact of Biosolid-Compost, Manure and Mineral Fertilizer on Alfalfa Yield and Soil Fertility.

With significant amount of municipal waste being produced in Southern California, nearby agricultural fields could be a feasible and sustainable destination of biosolid-composts produced in this region. Compost can be added to agricultural soils to improve fertility, water-holding capacity, infiltration, aeration, beneficial microorganism and tilth, or as mulch to reduce erosion, conserve water, control weeds and possibly creating a buffer to crop roots from heat. We assessed the impact of different rates of biosolid-compost, manure and mineral fertilizers in one alfalfa (Medicago sativa L.) field located in Newberry Springs, CA. In addition to three application rates (0, 11.2, 22.5 and 33.7 Mg ha^-1) of biosolid-compost we assessed the impact of dairy manure and mineral fertilizer on soil fertility, salinity, plant nutrition, water-holding capacity and yield. Initial soil fertility data for the field presented adequate to high nutrient content. All treatments were broadcasted over a 2 year old alfalfa field in February 2013, when the alfalfa was dormant. Average alfalfa yields among all five cuttings were significantly greater for the highest compost rate (33.7 Mg ha^-1) than the mineral fertilizers and the control treatments (3.8, 3.5 and 3.4 Mg ha^-1, respectively). Although the differences were not statistically different, treatments with higher rates of compost presented higher yields. None of the compost, manure or mineral fertilizer treatments had statistically significant impact on soil potassium, phosphorus and electrical conductivity collected at 0 to 0.15 m. Plant tissue samples indicated no significant differences phosphorus, potassium and heavy metals. In addition, non-replicated composite tissue samples of the compost and manure treatments indicate substantially higher K concentrations than the control treatment.