Yield and biochemical fruit quality of irrigated peach cultivars subjected to conventional farmer’s fertilization practices in warm production area

Water and fertilization management are the main concerns of farmers in order to achieve an economic yield and high fruit quality. This study evaluates conventional farmer’s fertilization practices in commercial peach orchards (Regueb region) and sets suitable nitrogen (N), phosphorus (P), and potassium (K) supplies to improve yield and fruit quality. Different farmers’ N-P-K supply practices (called FarmNPK) were applied during the different developmental stages of the growing season (S1 budburst and swelling; S2 flowering and fruit set; S3 fruit development; and S4 fruit ripening). Seven cultivars (Flordastar, Plagold5, Plagold10, Plagold15, Plawhite5, Plawhite10, and UFO3) were considered. Depending on cultivars and growth stage, the ranges of total N-P-K supplies were 95–208, 44–84, and 67–103 kg ha−1, respectively. Total fresh yield was quantified, and fruit quality (pomology, phenolic composition, main sugars, and organic acids) was determined in the mesocarp and exocarp. The results revealed that NPK supplies from 95–65–76 to 165–84–103 kg ha−1 induced the highest yield that varied between 50 and 68 kg tree−1, especially with high N supplies during S2. In all cultivars, high N and K supplies in S3 and S4 induced the best weight and fruit size, with the highest total soluble solid content in the fruit, while P supply appeared to be negatively correlated with total sugar content. Analysis of phenolic composition showed that flavan-3-ols varied between 209 and 7114 mg kg−1 DW. In conclusion, the optimum supply of N, P, and K at the appropriate stages, mainly S2 for N supply, and S3 and S4 improved color and ensured appreciable quality.