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ABSTRACT:The substantial generation of organic waste together with increasing interest in developing sustainable agriculture heralds an opportunity for mobilizing the recycling of these materials as a source of organic matter and nutrients into a viable management strategy option.A field experiment was conducted to evaluate the use of compost derived from waste produced by the winery and distillery industries in a drip-irrigated melon crop traditionally grown in the area where these wastes are generated. A randomized complete block design was used with four treatments consisting of three different dose levels of compost: 7 (D1), 13 (D2) and 20 (D3) t ha -1 and a control (D0) without the application of compost. The effects of these treatments on plant growth, nitrogen (N) and phosphorus (P) accumulation as well as fruit yield and quality were studied. The application of compost produced a slight increase in plant biomass accompanied by changes in the relative growth rate (RGR) and net assimilation rate (NAR). As a result, a significant improvement in fruit yield was observed in the plots amended with D2, which met all the requirements to obtain elevated yields. In terms of environmental correctness applications were below the limits established by a number of impact indexes. Additionally, the application of compost improved fruit quality resulting in an enhancement of Brix degrees. Although the potential effects of N and P derived from compost were partially masked by other inputs of these nutrients into the system (N in irrigation water, P supplied through fertigation), an effect of P was observed resulting in an increase in the number of individual fruits in the plots amended with compost.

The application of wastes from the wine-distillery industry as source of organic matter and nutrients could be a good option of agricultural management. This study is focused on soil nitrogen (N) mineralisation after addition of compost derived from this industry at different doses (7, 13 and 20 t ha -1 ). An aerobic soil incubation in controlled conditions was carried out to study N mineralisation from the soil-compost mixture as well as isolating the compost from the soil. The data were fitted to a non-linear regression obtaining low values of potentially mineralisable N (N 0 ) and constants of mineralisation (k) (from 81 to 104 mg kg -1 and from 0.008 to 0.013 L day -1 for the soil-compost mixtures, and from 42 to 71 mg kg -1 and from 0.009 to 0.015 L day -1 for the increasing doses of compost) which indicates that it is a mature compost very resistant to mineralisation. Nitrogen mineralised (NM) in the field during two growing seasons (2011 and 2012) of a melon crop was calculated through a N balance, taking into account N inputs and outputs in the soil-plant system. NM in the unamended plots accounted to 31 kg ha -1 and 24 kg ha -1 in 2011 and 2012, respectively, and increased proportionally to the dose of compost applied until 113 kg ha -1 and 98 kg/ha in the consecutive years. The constants of mineralisation obtained in the laboratory were adjusted by field temperatures to predict NM in the field and a general overestimation was observed. The best estimates were obtained when considering the mixture of soil and compost, which reflects the important role of the soil to evaluate N mineralisation caused by the addition of organic wastes.

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In this work, phosphorus (P) losses due to runoff were evaluated to understand the factors influencing the processes by which this element is lost. The forms of P present in organic wastes were studied using information provided by three P fractionation methods. All three methods contributed successfully to the understanding of the P forms present in wastes. However, it is difficult to compare the results from each to one another, as each protocol employs different extraction methods and times. In parallel, simulated rain systems were developed according to the "National Phosphorus Research Project" (2001) to characterize the P lost in the surface runoff generated. Experiments were performed on soil dosed with organic wastes applied both superficially and by mixing with the soil, and significant differences were found in the amounts of P determined to be in the runoff water of each, in both solution and particulate forms. Losses in experiments in which organic waste was applied to the soil surface were larger than those in experiments in which the samples mixed. In general, losses during the first rainfall event were the highest and particulate P forms predominated over dissolved forms. In mixed samples, significant differences in results were found depending on the type of waste used. Finally, a positive relationship was found between various P forms determined by sequential fractionation protocols and P losses by runoff.