Effect of synthetic and natural water‐absorbing soil amendments on photosynthesis characteristics and tuber nutritional quality of potato in a semi‐arid region

BACKGROUND The effect of water‐absorbing soil amendments on photosynthesis characteristics and tuber nutritional quality was investigated in a field experiment in a semi‐arid region in northern China in 2010–2012. Treatments included two synthetic water‐absorbing amendments, potassium polyacrylate ( PAA ) and polyacrylamide ( PAM ), and one natural amendment, humic acid ( HA ), both as single amendments and compound amendments ( HA combined with PAA or PAM ), and a no amendment control. RESULTS Soil amendments had a highly significant effect ( P ≤ 0.01) on photosynthesis characteristics, dry biomass, crop root/shoot (R/S) ratio and tuber nutritional quality. They improved both dry biomass above ground and dry biomass underground in the whole growing season by 4.6–31.2 and 1.1–83.1% respectively in all three years. Crop R/S ratio was reduced in the early growing season by 2.0–29.4% and increased in the later growing season by 2.3–32.6%. Soil amendments improved leaf soil plant analysis development value, net photosynthesis rate, stomatal conductance and transpiration rate by 1.4–17.0, 5.1–45.9, 2.4–90.6 and 2.0–22.6% respectively and reduced intercellular CO 2 concentration by 2.1–19.5% in all three years. CONCLUSION Amendment treatment with PAM + HA always had the greatest effect on photosynthesis characteristics and tuber nutritional quality among all amendment treatments and thus merits further research. © 2015 Society of Chemical Industry