Lychee yield, quality and nutrient uptake and accumulation as affected by application of medium and microfertilizers

Abstract:【Objectives】Medium and micro nutrients play an important role in the production of lychee. Excess or deficiency of some medium and micro elements will lead to the occurrence of relevant physiological diseases in lychee, resulting in the reduction of production and the decline of commercial rate and other negative effects. The purpose of this study was to investigate the effects of continuous application of medium and micronutrients on lychee yield, quality and nutrient accumulation and balance in tree-soil system within a relatively reasonable range of nitrogen (N), phosphorus (P) and potassium (K) supply, which will provide a scientific basis for the application of medium and micro nutrients in lychee production.【Methods】An on-farm experiment was carried out with or without medium and micro fertilizer application for four consecutive years, and the parameters of agronomic traits, yield, nutrient accumulation, quality and soil properties of lychee were obtained by destructive sampling after different fertilization measures.【Results】Compared with NPK (OPT) treatment, the combination of magnesium (Mg), zinc (Zn) and boron (B) with NPK (OPT + MN) treatment not only promoted the rapid shoot growth and increased the vitamin C content of lychee to some extent, but also enhanced the yield per year to different amplitude. Besides, the average fruit yield of lychee for four years with OPT + MN treatment significantly increased by 16.7%, which may be attributed to the fact that the application of micronutrient fertilizer increased the N nutrient and the synergetic promotion between calcium (Ca) and Mg, B and K, and Mg and N (P). Great differences in the absorption and accumulation of nutrient elements in plants existed, which were closely related to many factors, especially for crop species, varieties, mobility and interaction of nutrient elements and climate change. No significant difference was found in soil N content between OPT + MN treatment and OPT treatment. However, the N content in the tree with OPT + MN treatment was relatively higher than that with OPT treatment, and more N was accumulated in leaves. The results showed that OPT + MN treatment was beneficial to N absorption from soil and promoted N transport and accumulation in the leaves. The soil data also showed that the surplus of available P and K of soil with OPT + MN treatment was relatively higher than that with OPT treatment, and the value of available P and K in soil at the end of experiment increased sharply in comparison to the initial value of available P and K content regardless of the almost same level of P and K in shoot for both treatments, which implied that the medium and micro nutrients fertilizer application can effectively improve the content of available P and K in soil, and then maintain the fertility level of P and K under the current circumstances. Similarly, Ca, Mg, Zn and B were mainly distributed in the branches and trunk of lychee trees, and the latter promoted the transfer of much more Mg and Zn into leaves. And the concentration of Ca and B in fruit with OPT + MN treatment increased whereas the Zn concentration decreased. Moreover, OPT + MN treatment significantly increased the absorption and accumulation of Zn nutrient in tree body. The contents of Ca, Mg, Zn and B in leaves with OPT + MN treatment were higher than those with OPT treatment, but the changes of medium or micro element contents among different treatments were not completely consistent year by year. In addition, OPT + MN treatment promoted the increase of concentration of Ca and B in lychee leaves, and controlled the decrease of the concentration of Mg and Zn in lychee leaves. Nutrient contents of lychee leave in different years of the same orchard and body nutrients of lychee tree at different development stages of the same year varied greatly, especially for medium or micro elements. Simultaneously, by comprehensively analyzing the soil data, it was noticed that the content of exchangeable Ca and Mg in soil decreased to some extent compared with the initial test value, and the content of available B in soil maintained at the same level with the initial value, while the content of available Zn significantly increased, which further explained the highest accumulation of zinc in the whole plant. Therefore, the results showed that the amount of exogenous Ca and Mg should increase to maintain the basic level of Ca and Mg nutrients in the soil and to promote the transfer of more Ca and Mg nutrients to the aboveground under the current circumstances. Moreover, noteworthy difference was observed in nutrient contents and accumulation distribution characteristics of different parts of lychee in different years with the same treatment or in different fertilization treatments within the same year for the influence of various factors, such as the climate change, temperature, precipitation, fertilization, pest control and so on.【Conclusion】In view of the variability of medium and micro nutrient contents in lychee trees and symptom hysteresis of nutrient imbalance, it is advocated that supplement of corresponding deficient nutrients (especially Ca, Mg, Zn and B) is reasonable in lychee orchards based on soil test results. In addition, appropriate amount of soil amendment or lime should be applied to ameliorate the soil acidification in lychee orchards, which can help to realize nutrient balance between soil and lychee trees, so as to achieve the effect of quality improvement and yield increasing.