Soil Management and Supplemental Irrigation Effects on Potato: II. Root Growth

This study was conducted to determine if supplemental irrigation and/or application of soil amendments rich in organic matter can improve root growth of potato (Solanum tuberosum L.). Root length density (RLD) and root dry matter production of potato were studied under two levels of supplemental irrigation (nonirrigated check vs. moderate irrigation) and two levels of soil amendments [none vs. amended with compost and manure from beef cattle (Bos taurus L.)] during 1993 and 1994. Ameudments significantly increased RLD during both growing seasons and these increases occurred consistently throughout each growing season. Irrigation effects were not observed in 1993, while irrigation significantly increased RLD during 1994. Approximately 85% of the root length was concentrated in the upper 30-cm layer of the soil. The supplemental irrigation and soil amendment treatments did not affect the proportional distribution of roots among the soil layers. Root-to-shoot ratio was not affected by irrigation or amendment during either growing season. The RLD and leaf area index (LAI) at all four sample dates during 1994 were significantly correlated with final tuber yields, indicating that growth patterns early in the season were important in establishing the productivity of the potato crop. Root length density tended to have a higher correlation with yields than did LAI (r = 0.58 * to 0.80 ** vs. 0.51 * to 0.68 ** ).