Case Study on the Effects of Sodium Carboxymethyl Cellulose and Biostimulants on Physiological and Photosynthetic Characteristics, Yield, and Quality of Apples.

The problem of poor water and fertilizer retention in sandy soils can lead to physiological growth restriction and yield and quality decline in apples. Sodium carboxymethyl cellulose (CMC) formula can improve the soil structure and increase the water- and fertilizer-holding capacity of the soil, and Biogenic Stimulant (BS) can improve the drought stress resistance of crops and promote the physiological growth of crops. Considering that CMC and BS may improve the physiological characteristics of sandy soil apples, in this study, CMC was coupled with BS in sandy apples, and the effects on the physiological characteristics, yield, and quality of apples were systematically investigated. The results showed that CMC and BS could increase leaf N, P, and K content, with the greatest increases seen in the Y2C2 treatment (9.28, 0.61, and 0.56 g kg−1, respectively) compared with the CK treatment. The SPAD values of leaves following the coupled CMC and BS treatment compared to the CK treatment were elevated in the range of 4.47–24.29% at the flowering and fruiting stage, 2.84–26.50% at fruit expansion stage, and 6.64–19.41% at maturation stage. In the light response data of different treatments, the maximum net photosynthetic rate occurred in the Y2C2 treatment, and the net photosynthetic rate, transpiration rate, and stomatal conductance were all the highest in the Y2C2 treatment during the fruit expansion stage, with the net photosynthetic rate being higher than that of the CK treatment by 5.09 µmol m−2 s−1. The combination treatments of CMC and BS increased apple yield by 10.69 to 27.62% as compared to the CK treatment, and also increased soluble reducing sugar, soluble solids, and VC and reduced the titratable acid content. There was no correlation between the SPAD value during fruit expansion (p > 0.05) and the other physiological indexes (p < 0.05). Through the established functional relationship between the application rate of CMC and BS and apple yield, the recommended BS application rate of 27 kg ha−1 and CMC application rate of 20.625 kg ha−1 could yield up to 43,357.8 kg ha−1. [ABSTRACT FROM AUTHOR]