Two-dimensional fruit quality factors and soil nutrients reveals more favorable topographic plantation of Xinjiang jujubes in China

Jujubes (Ziziphus jujuba Mill.) are among the main agroeconomically important crops in Xinjiang, China, and those from this region have the highest production worldwide. However, the reason for the high quality of the jujubes in the region is unknown. In our current research, the total phosphorus (P), total nitrogen (N), organic matter (OM), available P, alkaline N and quick potassium (K) were quantitatively analyzed in soils collected from orchards in 11 geographical locations, counties or cities, in Xinjiang. Meanwhile, the P, total triterpenoids, soluble solids, polysaccharide and cyclic adenosine monophosphate (CAMP) contents were also used to indicate fruit quality. Based on the analyzed data, principal component analysis (PCA) and multiple regression analysis revealed a high correlation between soil nutrients and the quality of the Jun jujube, which was used as an example. Specifically, the total P and quick K contents significantly differed among the orchard soils. Moreover, they significantly affected fruit quality. Total P significantly affected the soluble solids and total triterpenoids contents and was negatively correlated with the former and positively correlated with the latter. In addition, the soluble solids and total triterpenoids contents were significantly affected by the quick K content; as the quick K content increased, the soluble solids content gradually increased, while the total triterpenoids content decreased. According to the response surface model, we suggest that when the total P and quick K contents in the soil in Xinjiang were 0.76 g/kg and 365.04 mg/kg, respectively, the optimal fruit quality was obtained. Therefore, two-dimensional analysis of fruit quality and soil nutrients showed that it is necessary to increase the total P and quick K contents in the soil used to grow jujubes in Xinjiang.