Effect of different water and combinations on the sustainable growth of chestnut sown seedlings

Chestnut (Castanea mollissima Bl.) is an important economic crop in Asia, and this study aimed to shorten the seedling cycle, improve seedling quality, and promote sustainable chestnut cultivation by identifying optimal water and fertilizer combinations. The experiment utilized a consistent seed source for the greenhouse nursery, selecting chestnut seedlings with similar growth after germination for further analysis. The study evaluated three levels of fertilizer treatments: S1 (CO(NH2)2 60 g/m2 + P2O5 27 g/m2 + K2O 60 g/m2), S2 (CO(NH2)2 45 g/m2 + P2O5 21 g/m2 + K2O 50 g/m2), and S3 (CO(NH2)2 30 g/m2 + P2O5 15 g/m2 + K2O 40 g/m2), and three irrigation levels: W1 (0.36 m3/m2), W2 (0.24 m3/m2), and W3 (0.12 m3/m2), resulting in nine treatment combinations. Growth parameters were measured, including seedling height, diameter, biomass, root morphology, soluble sugar, starch content, and photosynthetic rate. The results showed that with increasing water and fertilizer concentrations, the growth of chestnut seedlings differed significantly, with the ranking of height and diameter at the end of the experiment being: S1W2 > S1W1 > S2W3 > S2W2 > S2W1 > S3W3 > S3W2 > S3W1 > S1W3. The S1W3 treatment, with excessive fertilizer concentration, inhibited seedling growth. Biomass and root morphology were positively correlated with fertilizer concentration, except in the S1W3 treatment. Additionally, lower irrigation combined with higher fertilizer application enhanced soluble sugar, starch accumulation, and sugar photosynthetic rate. The optimal combination for promoting chestnut seedling growth was S1W2(Fertilization value CO(NH₂)₂ 60 g/m2 + P2O5 27 g/m2 + K2O 60 g/m2 (S1), Irrigation value 0.24 m3/m2 (W2)), suggesting that balanced fertilizer and water management can improve seedling quality and support sustainable chestnut cultivation.