Ag1000 Soil Amendment Increased Root Growth and Intrinsic Leaf Water Use Efficiency in Corn.

Shortage of water is a major factor limiting the crop production on arid and semi-arid regions of the world. One important aspect of crop management is to increase the capacity of plant roots in mining larger soil volumes and thus ameliorate the negative impact of drought stress. Recent years has seen an increased use of beneficial microorganisms in promote soil health and enhance plant growth performance. Despite the reports of yield improvement or water savings associated with the use of some soil amendment, definite and quantifiable results of the plant physiological responses to the applications of beneficial soil microorganisms are not well appreciated. This knowledge gap impedes the development of more efficient application protocols leading to significant agronomic results at the farm scale.  We report an on-going research on irrigated corn using the ag1000 soil amendment conducted in southwest Texas. The main objectives are to characterize plant physiological and root rhizosphere responses, as well as the realized crop yields, to the soil amendment. The work has implications for improving agricultural production efficiency by utilizing current understanding and technology of soil-rhizosphere interactions. The experiment was conducted in one quarter of a center-pivot irrigated field at the Uvalde Research and Extension Center, Uvalde Texas. The pivot quarter was divided into six sections radially for three irrigation treatments each replicated twice (100% irrigation based on potential evapotranspiration and crop coefficient; 75% and 50% reduced irrigation). The corn seeds (variety Dekalb 6469) were planted March 20, 2014 in 40-inch rows with individual seeds 78- inches part in a row. Across the pivot quarter, two rows of corn were selected for soil amendment using Ag1000 and nearby two rows of corn were used as control. The ag1000-treated rows and the control rows were located in the middle of the pivot quarter and were separated by two rows of corn in between. The ag1000 solution was applied in a 40 ft long strip within the treated two rows in each of the designated irrigation section (6 in total). The rate of ag1000 application was 10 gallons/acre, applied once every two weeks, started two weeks after emergence. The applications were done using a backpack sprayed one day prior to irrigation. Within each of the 40-ft long plots, one rhizotron tube and one neutron probe tube were installed for root and soil water measurement. The rhizotron tubes were installed at 45 degree angle to a depth of up to 1 m. Soil water content was measured once every week and the root image was taken once every three weeks. Leaf photosynthetic rate and stomatal conductance was measured using a LI-6400 Portable Photosynthetic System on top fully expanded leaves in major development stages. Close to harvest, rhizosphere microbial community will be characterized using sampled soil-root sample from the field plots. Our ongoing results indicate a significant improve root growth in the ag1000 treated plots as compared with the control. While a full image analysis is still in progress, we surveyed 600 rhizotron images taken on June 2, 2014 from the top 43 cm soil depth in 12 rhizotron tubes. Initial inspection indicates that 57% of the images from the ag100 treated plots had roots, while only 24 % of the control plot images had roots. The Kruskal-Wallis test shows that the difference is significant (p<0.05). Our gas exchange rate measur4ed on May 15 and June2, 2014 during the midday hours suggests a significant increase in intrinsic water use efficiency (defined as photosynthetic rate divided by stomatal conductance) in treated plots as compared control (p<0.05), suggesting the potential water saving benefits of using the ag1000 soil amendment. Crop yield data as well as root rhizosphere community features are to be collected in August, which can be used to provide further evidence of the benefits of ag1000 soil amendment for increasing agricultural production efficiency.