Testing Soil Fertility, Tomato Yield and Quality, and Residual Spinach Performance under Integrated Fruit-Waste Compost, Manure and NPK Fertilization

This study was conducted in 2020-2021 in the field conditions of Tokat Gaziosmanpaşa University. The study, effects of different compost (tomato-apple-grape) applications on yield, quality, soil properties of tomato plants, and second crop spinach cultivation were examined under field conditions. The experiment was carried out according to randomised blocks design with 3 replications. In this study, 18 different treatments including control (with/without fertilizer) [(T0) Control (no fertilizer); (T1) Control + NPK; (T2) 10 t/ha Tomato compost; (T3) 20 t/ha Tomato compost; (T4) 10 t/ha Apple compost; (T5) 20 t/ha Apple compost; (T6) 10 t/ha Grape compost; (T7) 20 t/ha Grape compost; (T8) 10 t/ha Farmyard manure; (T9) 20 t/ha Farmyard manure; (T10) 10 t/ha Tomato compost + NPK; (T11) 20 t/ha Tomato compost + NPK; (T12) 10 t/ha Apple compost + NPK; (T13) 20 t/ha Apple compost + NPK; (T14) 10 t/ha Grape compost + NPK; (T15) 20 t/ha Grape compost + NPK; (T16) 10 t/ha Farmyard manure + NPK and (T17) 20 t/ha Farmyard manure + NPK] were applied. At the end of the study, compost treatments provided a significant yield increase compared to the control treatment. Especially tomato, and grape compost applied at the same dose provided more increase in yield compared to farmyard manure. NPK fertilizer application, together with compost or farmyard manure, also increased yield. In spinach cultivation in the same plots after tomato harvest, the highest biomass was obtained from the plots with farmyard manure, and grape compost application. When spinach was grown without any fertilisation after farmyard manure, and compost application, 555.76% increase in biomass was obtained in farmyard manure application compared to control, and 376.25% increase compared to NPK fertilisation, 541.53% increase was obtained in compost application compared to control, and 366.62% increase was obtained compared to NPK fertilisation. The use of compost in tomato, and second crop spinach cultivation under field conditions provided a significant yield increase in both tomato, and spinach. At the same time, it was found that using compost and farmyard manure increased the soil's organic matter content and levels of some macronutrients, but only had a limited effect on the soil's pH value. Examining the quality characteristics of tomato fruit revealed that the applications had a positive effect on important parameters such as soluble dry matter content. These results demonstrate that composting not only increases yield, but also has a lasting positive effect on the cultivation of subsequent crops by improving soil fertility and product quality.