Using Digestate and Biochar as Fertilizers to Improve Processing Tomato Production Sustainability

The principal goal of the organic farming system (OFS) is to develop enterprises that are sustainable and harmonious with the environment. Unfortunately, the OFS yields fewer products per land than the non-organic farming system in many agricultural products. The objective of our study was to assess the effects of digestate and biochar fertilizers on yield and fruit quality of processing tomato produced under the OFS. The experiment was carried out in Po Valley, during the 2017 and 2018 growing seasons. Liquid digestate (LD), LD + biochar (LD + BC) and pelleted digestate (PD) were evaluated and compared to biochar (BC) application and unfertilized control. The results showed that plants fertilized with LD + BC recorded the maximum marketable yield (72 t ha−1), followed by BC (67 t ha−1), PD (64 t ha−1) and LD (59 t ha−1); while the lowest production (47 t ha−1) was recorded in unfertilized plants. Over the two cropping seasons, LD + BC, BC, PD, and LD, increased fruit number per plant (+15%), fruit weight (+24%), Brix t ha−1 (+41%) and reduced Bostwick index (−16%), if compared to the untreated control. Considering the overall agronomic performances, digestate and biochar can be useful options for increasing yield and quality of processing tomato production in the OFS. Hence, these fertilizers can be assessed in future research both on other crops and farming systems.