Effect Of Water-soluble Humic Acid Fertilizer On Drought Resistance Of Potato

This study focused on water-soluble humic acid fertilizer’s influences in potato’s morphological index, leaf photosythesis, leaf and root physiological index, and nutritional quality under four circumstances-full drought, semi-drought, semi-humidity and natural rainfall, which would establish a solid and scientific foundation in development and application of water-soluble humic acid fertilizer. The main findings are as follows:1、With different treatments in water gradient, the water-soluble humic acid fertilizer can increase potato’s plant height, stem diameter and yield-plant height increased by 0.87%～20.33%, stem diameter increased by 1.33%～32.85% and yield increased by 6.01%-23.89%. The water-soluble humic acid fertilizer played the most important role in the arid condition treatments.2、Spraying water-soluble humic acid fertilizer can strengthen leaf photosynthesis. With treatments, the SPAD value of leaves increased by 0.95%-25.37%, compared with the controls’. The photosynthetic rate increased by 1.4%-24.72%, transpiration rate reduced by 1.89%～17.63%, and stomatal conductance reduced by 1.67%-15.87%. The effects of water-soluble humic acid fertilizer were different under diverse water gradients, and the effect was best in the arid treatments.3、With spraying water-soluble humic acid fertilizer, the content of MDA in leaf reduced by 4.1%～24.35%, and reduced by 4.15%-26.96% in root. In addition, REC of leaf reduced by 2.55%～23.73%. The water-soluble humic acid fertilizer reduced membrane permeability of leaf and root and ease the damage on cell membrane from drought. The lower water gradient was, the better effect of water-soluble humic acid fertilizer did.4、With spraying water-soluble humic acid fertilizer, free-proline in leaf and rood increased by 2.97%～36.54% and 0.86%-25.77% respectively, and solube protein increased by 1.94%～42.81% and 2.75%～24.26% respectively, compared with control.The water-soluble humic acid fertilizer can increase free-proline, and it got the larger increase and higher value in the arid treatments, while its effect on solube protein showed no higher value.5、With spraying water-soluble humic acid fertilizer under different water gradients, SOD activity in leaf and root increased by 2.56%-35.89% and 2.75%～26.48% respectively, POD activity increased by 3.16%～49.12% and 5.12%～48.75% respectively, and CAT activity increased by 2.25%-33.92% and 2.56%-53.06% respectively. The water-soluble humic acid fertilizer can increase the protective enzyme activity, keep metabolic balance of reactive oxygen species better and guarantee the growth of potato.6、 Under different water gradients, root activity was accelerated byl.5～44.85% with treatment of water-soluble humic acid fertilizer, indicating that water-soluble humic acid fertilizer had a positive effect on increasing the root activity. Meanwhile, dry conditions and continuous growth would enhance the effects.7、Under different water gradients, the water-soluble humic acid fertilizer can increase tuber nutritional quality-antioxidant activity in tuber increased by 8.43%～31.88%, total phenolics in tuber increased by 1.67%～35.71% and chorogenic acid in tuber increased by 4.3%-41.28%. And the water-soluble humic acid fertilizer attached more importance in the arid condition.8、The correlation analysis showed that plant height, photosynthetic rate of the leaves, stomatal conductance, root activity have an extremely significant correlation with yield; the soluble protain content in leaves have an extremely significant correlation with yield, the free-protain content in roots have an extremely significant correlation with yield; MDA, REC, SOD have an extremely negative correlation with yield. Above all, those indicators could be an effective index to judge drought resistance and yield of potato under different water conditions.