Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2014
Publication Date: 7/18/2014
Citation: Logsdon, S.D., Singer, J., Prueger, J.H., Hatfield, J.L. 2014. Comparison of corn transpiration, eddy covariance, and soil water loss. Soil Science Society of America Journal. 78:1214-1223. DOI: 10.2136/sssaj2014.01.0044. Interpretive Summary: Crops may take up water at different rates for different parts of the field. This study showed that the rate of water uptake was greater for the upland area than for the lowland area during silking and pollination of corn. Crop development was delayed in the upland area, but final plant growth and grain yield were similar for the upland and lowland areas (131 vs. 134 bushels/acre). For the upland area, measurements of crop water uptake and soil water loss to 4.3' (rooting depth) were similar except for soil water fluctations after a rain due to water being funneled down the stem. For the upland area, the soil was dried to wilting point for the depths 1.6 to 3', but there was available water above and below these depths. For the lowland area, soil water loss to 2.3' (just above the water table depth), was greater than crop water uptake for one and a half weeks. Then soil water increased even as the corn continued to take up water, due to water movement up from the water table. This information is of interest to scientists, crop consultants, and farmers who want to utilize spatial data on yield and soil properties to improve precision farming planning.
Technical Abstract: Stem flow gages are used to estimate plant transpiration, but only a few studies compare transpiration with other measures of soil water loss. The purpose of this study was to compare transpiration from stem flow measurements with soil water changes estimated by daily neutron probe readings. Monitoring at shoulder and toeslope positions continued for 14 d during the corn (Zea mays L.) early reproductive stage. During this time, the cumulative mean transpiration loss at the shoulder position was 88 mm and 71 mm for the toeslope position. The cumulative soil water loss to the 1.3 m depth was 93 mm, but 47 mm to the 0.7 m depth for the toeslope position. During this time the water table depth at the shoulder position dropped from 1.6 to 2.3 m below the soil surface, whereas the water table depth only dropped from 0.6 to 0.9 m at the toeslope position. For the toeslope position, some of the water from below the water table had moved up into the root zone. The soil at the shoulder position had dried to wilting point, but only from 0.5 to 0.9 m depth. At the shoulder position, crop development was delayed 3 d at R1 and 8 d at R6 compared with the toeslope position. In spite of dry soil at the shoulder position, the grain yields were similar (9020 vs 8774 kg ha-1) for the toeslope and shoulder positions. Stem flow gages were a useful tool to distinguish landscape position differences in transpiration rate.