Soil chemical properties, 'Guanximiyou' pummelo leaf mineral nutrient status and fruit quality in the southern region of Fujian province, China

Abstract

Three hundred and nineteen ‘Guanximiyou’ pummelo (Citrus grandis) orchards from Pinghe county, the southern region of Fujian province, China, were selected for this study. The objectives were to determine (i) the soil and leaf nutrient status, (ii) the relationships between leaf mineral elements and the corresponding soil elements, and (iii) the relationships between fruit quality and mineral nutrients. The results showed that soil acidification was a major problem in these orchards, with an average pH of 4.34. Soil acidification affected the availability of soil N, P, Ca, Mg, S, B, Cu and Zn and the levels of organic matter (OM) and cation exchange capacity (CEC), thus inducing soil and leaf nutrient imbalance. Indeed, severe nutrient imbalance existed in these orchard soils. 77.4% and 65.8% of soils were sub-optimum in exchangeable Mg and Ca, while 96.6% and 82.1% of soils were super-optimum in available S and P, respectively. Besides, severe nutrient deficiencies and excesses co-existed in leaves. 46.8% and 35.6% of leaves were deficient in N and Mg, while 74.8% and 70.4% of leaves were excess in B and Cu, respectively. Regressive analysis showed that leaf content of mineral elements was poorly related with the available content of the corresponding soil elements, respectively. In some orchards, severe juice sac granulation, an important factor affecting fruit quality, was observed. Regressive analysis indicated that Mg, S, Cu and Mn played a role in juice sac granulation of fruits. In conclusion, soil acidification might lead to severe soil nutrient imbalance, thus inducing leaf nutrient imbalance, eventually impairing fruit quality parameters such sac granulation.