Dynamic changes and correlation of nutrient accumulation in the fruit of red pitaya

【Objective】 In order to understand the development and growth of the red pitaya fruit and the dynamics of nutrient accumulation and their correlation in Hainan, to provide a theoretical basis for scientific fertilization of pitaya in this area.【Method】 Using the four different growth stages of the red pitaya at 8, 16, 24, and 32 d after flowering, the agronomic traits such as the horizontal and vertical diameters and dry weight of the fruit and nitrogen(N), phosphorus(P), potassium(K), calcium(Ca) and magnesium(Mg). Explored the formation law and dynamic changes of mineral nutrients of red pitaya fruit, and to analyze the correlation between peel and pulp mineral nutrients.【Result】 The early stage of fruit development(the first 24 d after flowering) was mainly the accumulation of dry matter. The peak growth period was 16 to 24 d after flowering, and the growth rate of horizontal and vertical diameter and water content were large. In the later stage of fruit development(24-32 d after flowering), the dry weight of the peel was reduced, mainly due to the weight gain and color change of the pulp. With the growth and development of pitaya, the mineral nutrient accumulation in the pulp showed an overall upward trend, and the mineral nutrient accumulation in the peel and the whole fruit showed an overall upward trend and then a downward trend. The fruit's demand for N, K, and Ca was high. The eight elements of K, Ca, Mg, sulfur(S), ferrum(Fe), copper(Cu), zinc(Zn), and boron(B) between the peel and the pulp had significant(P<0.05, the same below) or extremely significant positive correlation with each other(P<0.01, the same below). There was significant positive correlation between peel manganese(Mn) and pulp Mn and Cu, and extremely significant positive correlation with Zn and B elements, but there was no significant correlation between Mn and other elements(P>0.05). The accumulation of mineral nutrients in the whole growth period of the peel was K>N>Ca=Mg>P>S>Fe>Mn>Zn>B>Cu, and the accumulation of mineral nutrients in the whole growth period of the pulp was:K>N>Mg>Ca>P>S>Fe>Mn>Zn>B>Cu, the accumulation of mineral nutrients throughout the fruit growth period was:K>N>Mg>Ca>P>S>Fe>Mn>Zn>B>Cu.【Conclusion】 The early stage of red pitaya growth(the first 24 d after flowering) and development is mainly due to the expansion of the fruit, and attention should be paid to the application of N fertilizer and water management. The late stage of pitaya development(24-32 d after flowering) is mainly for the color change of the fruit. The application of K fertilizer and Ca fertilizer should be paid attention to, and the supplement of trace element fertilizers such as Mg and B should be conducted based on soil fertility.