Evaluation of synthetic and natural water absorbing soil amendment on potato production in a semi-arid region.

Effect of synthetic and natural water absorbing soil amendments on soil moisture content, yield and water use efficiency (WUE) of potato production was investigated in a field experiment in a semi-arid region in northern China in 2010-2012. Treatments included two different water absorbing synthetic amendments (potassium polyacrylate-PAA, polyacrylamide-PAM) and one natural amendment (humic acid-HA), both as single amendments, and compound amendments (natural combined with a synthetic) and no amendment control. Soil amendments significantly (P≤0.05) affected soil moisture content over the entire potato growing season, particularly in the 0-40 cm layer, except for periods with adequate precipitation. Soil amendments increased fresh tuber yield by 6.2%-23.6%, 4.2%-32.9%, and 12.0%-26.2%, improved commercial tuber proportion of the total yield by 1.7%-10.1%, 3.2%-16.6%, and 2.9%-13.7% and increased WUE by 11.1%-23.8%, 4.1%-34.7%, and 19.8%-38.6% in 2010, 2011, and 2012 respectively. The compound treatment, PAM plus HA, had the highest soil water content, yield and WUE in all three years. Cost benefit analysis based on present amendment costs and potato prices, showed that the single synthetic amendment PAM had the highest economic return in all three years; economic return was improved by 138, 413, and 795 USD/ha in 2010, 2011, and 2012 respectively compared with the non-application control. The PAM plus HA treatment shows the most promise in improving soil water holding capacity and potato production, and deserves further research.