Fertigation with Wastewater and Vermicompost: Soil Biochemical and Agronomic Implications

To study how wastewater(WW) and different organic sources(humic substances or vermicompost) affected soil chemical and biochemical fertility and agronomic productivity in field-grown melon, an experiment arranged in a randomized complete block design with three replications was conducted with the following treatments: three different mixtures of irrigation water(100% WW, 50% WW with 50% groundwater, and 100% groundwater) and, for each WW treatment, four different organic fertilization treatments of control without organic matter application(CK), vermicompost used as surface mulch(SM), vermicompost incorporated into the soil(VC),and humic substances extracted by vermicompost(HS). Chemical and biochemical results indicated an improvement in soil fertility,suggested by the increase in soil organic carbon and nutrient(nitrate and macro- and microelements) contents and in soil microbial activities(hydrolytic and oxidative enzymes), in particular in the VC treatments. In addition, even soil potential metabolism was stimulated by WW combined with organic treatments, as highlighted by the increase in the metabolic(dehydrogenase activity/watersoluble carbon) and nitrification indices(NO-3and NH+4). Melon productivity confirmed these results, with the highest yield and melon quality in the VC treatments irrigated with 100% WW. In conclusion, the combined use of WW and organic amendment,recovering both mineral and organic nutrients from these kinds of recycled materials, was effective in the improvement of soil quality and crop productivity.