Effects of Potassium Application on Potassium Nutrition and Crude Fat Content of Walnut

Effect of potassium sulfate spray on the changes of crude fat content during development of different walnut varieties

The accumulation of crude fat in walnut kernels was not affected by the variety and potassium spray. The crude fat content of the kernels remained stable until July 5, and the crude fat content of the kernels accumulated exponentially after entering the oil-conversion stage, as shown in Figure 2. After analysis of variance of crude fat content of kernels at different sampling periods, the results showed that: on July 17 and July 25, samples of walnuts, Xi 2 and Shan 1, and 2 varieties of kernels had significant differences in crude fat content. The effect of potassium was not significant; on the contrary, the sampled walnut on August 7 was significantly lower than that of the control, but the effect of the variety was not significant.

2.3 Correlation Analysis of K Content in Walnut Peel and Crude Fat Content in Seeds

During the whole fruit growth period, the curve of the potassium content of the peel of the fruits and the change curve of the crude fat content of the seeds maintained a similar trend (Figs. 1 and 2). From the table, the potassium content of the walnut of the walnut fruit treated by the 4 treatment was significantly positively correlated with the crude fat content of the seed kernel (4 treatments P<0.01), and the linear relationship between the potassium content of the walnut peel and the crude fat content of the kernels. The slopes of the relationship were 10.235 (West 2, CK), 10.296 (West 2, potassium spray), 11.096 (Shaan 1, CK), and 11.949 (Shaan 1, potassium spray), respectively. The slope was greater than that of the control. The slope of Shaan 1 was greater than that of Xi 2, indicating that the accumulation of potassium in the former was more effective than the latter in the accumulation of crude fat. The correlation coefficients of the treatments reached 0. 9634 (West 2, CK), 0. 9465 (West 2, potassium spray), 0.913 (Shaan 1, CK), 0. 9515 (Shaan 1, potassium spray).

3 Discussion

In the study of cultivation of high oil crops, there is no shortage of research reports on the application of potassium to increase the fat content of kernels. The study also found that there was a very significant positive correlation between the potassium content in the walnut peel and the crude fat content of the seed kernel, which is basically the same as previous studies. Therefore, this can be considered as a nutritive characteristic of walnut fruit development. The study found that the potassium spray treatment had no significant effect on the K content and the crude fat content of the walnut kernels. This may be related to the high soil available K content (455.97 mg/kg, more than one-time excess of 170 mg/kg of soil available potassium supply index). It can be seen that the effect of potassium application is not obvious on the potassium-rich soil, and the excessive fat content of the kernels is also reduced due to excessive potassium. However, spraying K2 SO4 treatment still resulted in a slight increase in the weight and yield of the two walnut varieties compared to the control. Therefore, the main contribution of potash fertilizer is to increase production, and thus also increase oil production per hectare. During the oil conversion period of walnut fruit development, the sampling and measurement results showed that the K content and the crude fat content of kernels in walnut variety Xi 2 were significantly higher than those in Shan 1 . Leaf analysis results showed that the K contents in the leaves were 1.43 % (West 2CK), 1.39 % (West 2 spray K), 0.84 % (Shaan 1CK), and 0.91 % (Shaan 1 spray K), respectively. The potassium content in the West 2 leaves was significantly higher than that in Shaan 1, although the K in the leaves was higher than the lower limit of the leaf fertilization potassium nutrient reference standard (0.75% to 1.25 %), field observations revealed that the walnut fruit development In the late period, there were still some K-deficient symptoms in the leaves of Shaanxi 1 . Hunter et al. found that the high content of potassium in the leaves of American pecan nuts has a high content of fat in the nuts, and vice versa. Therefore, under the same conditions, the walnut variety Xi 2 can obtain higher oil content than Shaan 1, and it is also more suitable for promotion as a high-oil walnut processing variety.