Composts as alternative to inorganic fertilization for cereal crops.

The use of treated organic products as fertilizers and soil amendments not only results in economic benefits for the small-scale farmer, but it also reduces pollution due to reduced nutrient run-off and N leaching. In this work, the feasibility of using composts as fertilizers and soil improvers has been evaluated at the field level, in barley and soft wheat crops (two successive cultivations of each crop). The applied treatments consisted of two commercial composts (compost manure and sewage sludge compost) added to the soil either alone (T1 and T3) or in combination with inorganic fertilizers (T2 and T4) and a conventional mineral fertilization (T5). Physical, physical-chemical, chemical, microbiological, and biochemical parameters were determined in the soil after each harvest. In both barley and wheat crops, soils treated with composts showed higher organic C, humic substances, and humic acid contents than the inorganically fertilized soil, as well as higher contents of water-soluble P, K, Ca, Mg, and S. In both successive crops, all treatments led to similar yields of total barley and wheat vegetal material (straw + ears) and grain, differences between treatments being not statistically significant (p ≤ 0.05). Organically treated soils showed higher microbial size and activity than inorganically treated soils as well as higher water-holding capacity. It can be concluded that quality organic composts can be used, at suitable rates, alone or in combination with inorganic fertilizers, as a good alternative to inorganic fertilization for cereal cultivation, improving soil characteristics while giving similar yield and crop quality than conventional inorganic fertilization.