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United States Department of Agriculture

Agricultural Research Service

Research Project: SALINITY AND TRACE ELEMENTS ASSOCIATED WITH WATER REUSE IN IRRIGATED SYSTEMS: PROCESSES, SAMPLING PROTOCOLS, AND SITE-SPECIFIC MANAGEMENT Title: The effect of total carbon on microscopic soil properties and implications for crop production

Authors
item Lebron, Inma -
item Mcgiffen, Jr, Milton -
item SUAREZ, DONALD
item SUAREZ, DONALD

Submitted to: Journal of Arid Land
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 18, 2012
Publication Date: June 1, 2012
Citation: Lebron, I., McGiffen, Jr, M.E., Suarez, D.L. 2012. The effect of total carbon on microscopic soil properties and implications for crop production. Journal of Arid Land. 4(3):251-259.

Interpretive Summary: Maintaining good soil structure is a necessary condition for sustaining a productive irrigated agriculture. Addition of organic matter may increase nutrient availability but it will also moderate fluctuations in soil temperature, increase microbial activity, increase soil water retention and most importantly potentially increase crop yield. Less is known about the direct effect of changes in soil structure on crop production. A field experiment was conducted to study the effect of summer cover crop and an in-season management system on soil structure. Management systems were organic, integrated management, and conventional production systems. Disturbed and undisturbed soil cores were collected at the end of the third year and used for laboratory experiments to measure physical, chemical, and hydraulic properties. Image analysis was used to quantify soil structure properties. We found that total soil carbon was positively correlated with porosity, saturation percentage, and pore roughness. Pore roughness correlated positively with crop production in general and with marketable production in particular. We found that the higher the complexity of the pore space the more water retained in the soil, which is beneficial as it may reduce plant water stress. These results provide new information on the effects of adding organic matter to soils and the impacts on soil physical properties. The information should be of interest to researchers examining the impacts of organic farming on soil, extension specialists and farm advisors.

Technical Abstract: Soil structure is a dynamic property affected by physical, chemical, and microbiological processes. Addition of organic matter to soils and the use of different management practices have been reported to impact soil structure and crop production. Moderation in soil temperature and increases in microbial activity and soil water retention are often suggested as reasons for the rise in crop yield when organic matter is added to the soil. Less is known about the direct effect of changes in soil structure on crop production. A field experiment was conducted to study the effect of summer cover crop and in-season management system on soil structure. The experiment was a nested design with summer cover crop as the main plot and management system as the subplot. Summer cover crops were cowpea (Vigna unguiculata L. Walp.) incorporated into the soil in the fall (CI), cowpea used as mulch in the fall (CM), sudangrass (Sorghum vulgare) incorporated into the soil in the fall (S), and dry fallow or bare ground (B). Management systems were organic (ORG), integrated management (ICM), and conventional (CNV) systems. A rotation of lettuce (Lactuca sativa L.) and cantaloupes (Cucumis melo L) was cultivated in the plots for three consecutive years using the same cover crops and management systems for each plot. Disturbed and undisturbed soil cores were collected at the end of the third year and used for laboratory experiments to measure physical, chemical, and hydraulic properties. Image analysis was used to quantify soil structure properties using a scanning electron microscope on thin sections prepared from the undisturbed soil cores. We found that total soil carbon was correlated with porosity, saturation percentage, and pore roughness. Pore roughness correlated with crop production in general and with marketable production in particular. We found that the higher the complexity of the pore space the more water retained in the soil, which may increase soil water residence and reduce plant water stress.

Last Modified: 8/19/2014
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