Evaluation of different organic matrices used as fertilizers in open fild horticulture: production and environment approach

Intensive agriculture has caused social and environmental problems worldwide over the past few decades and sustainable agriculture represents an important alternative to solve this problem. Organic fertilization with municipal solid waste (MSW) compost and anaerobic digested residues (ADRs) in horticulture offers an important step towards sustainability. On the other hand, nitrogen use efficiency (NUE) knowledge helps to better adjust N-base fertilization in order to prevent environmental problems. In addition, CO2 released by the crop production process (CO2CPP), CO2 fixed in soil (CO2Soil), CO2 fixed in dry marketable yield (CO2MY) and CO2 balance are valuable information that demonstrate opportunities for horticulture to mitigate climate change. Two experiments were conducted using ADRs and MSW-compost as fertilizers in two crop rotations: the first one from 2009 to 2011 and the second one from 2007 to 2011, both at the experimental farm of the University of Padua in Italy. Five fertilization treatments were evaluated in both experiments, with a mineral control and an unfertilized control. For ADRs, three treatments were included in which 50, 75 and 100% of the N (T50, T75 and T100) was supplied with this organic matrix. For the second experiment, the three treatments included were T50, T100 and T200, in which 50, 100 and 200% of the N was supplied by MSW-compost. NUE was calculated for all crops and rotations in both experiments. CO2CPP, CO2Soil , CO2MY and CO2 balance were ascertained for the crops and rotations growing with the MSW-compost. Finally, the soil’s organic carbon and total nitrogen were determined in plots fertilized over a five year period with MSW-compost in both rotations. ADRs and MSW-compost are valuable organic materials that can be used as fertilizers in horticulture. Some results obtained are: 1) for early spring crops, a combination of 50% organic and 50% chemical N represents a good fertilization option. For example, onions growing with MSW-compost presented a low N recovery (REC) and were fertilized with high doses of N, this represents a high risk of N leaching, T50 presented the highest marketable yield and REC for that crop. 2) For summer crops, high temperatures during the crop cycle influenced the trend of similar REC for all ADR treatments; moreover, T100 presented the highest marketable yield for butterhead and iceberg lettuces in 2010. 3) For some fall-winter crops, ADR and MSW-compost treatments did not show REC as much as the mineral treatment, mainly because of the closeness of the fertilization and the transplanting times (i.e., applying organic fertilizers some weeks before transplanting can improve organic N availability.) However, T50 had the highest N-uptake and REC for late radicchio 2010 fertilized with ADRs and chicory 2011 growing with MSW-compost. 4) On the other hand, in the plots fertilized with MSW-compost, T100 enhanced soil’s organic carbon and total nitrogen. Crop rotation helped to improve C:N, rotation A presented the higher content SOC. 5) Finally, T50 fixed the highest amount of CO2MY in both rotations. Treatment T200 was less sustainable because of the higher CO2CPP and the lower CO2Balance. Rotation A fixed more CO2Soil than rotation B.