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Influence of Tillage and Deep Rooted Cool Season Cover Crops on Soil Properties, Pests, and Yield Responses in Cotton

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Open Journal of Soil Science 2016年第10期6卷 149-158页

作者： Michael W. Marshall Phillip Williams Ali Mirzakhani Nafchi Joe Mario Maja Jose Payero John Mueller Ahmad Khalilian edisto Research & Education Center (edisto rec) Clemson University Blackville SC USA Department of Agricultural and Environmental Sciences Clemson University Clemson SC USA

Soil compaction is a significant problem in the Southeastern USA. This compacted zone or hardpan limits root penetration below this layer and reduces potential yield and makes plants more susceptible to drought induced stresses. Soil compaction in this region is managed using costly annual deep tillage at or before planting and there is a great interest in reducing and/or eliminating annual tillage operations to lower production costs. Deep rooted cool season cover crops can penetrate this compacted soil zone and create channels, which cash crop roots, such as cotton, could follow to capture moisture and nutrients stored in the subsoil. The cool season cover crop roots would reduce the need for annual deep tillage prior to planting, increases soil organic matter, which provides greater water infiltration and available water holding capacity. Field studies were conducted for two years with three different soil series to determine the effects of tillage systems and cool season cover crops on the soil chemical and physical properties, yield responses, and pest pressure. Results showed that cool season cover crops significantly reduced soil compaction, increased cotton lint yield and soil moisture content, reduced nematode population densities, and increased soil available P, K, Mn, and organic matter content compared to the conventional no-cover crop.

关键词： Cover Crop Cotton Soil Compaction Nematodes Soil Water Content Tillage

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Evaluating Reflected GPS Signal as a Potential Tool for Cotton Irrigation Scheduling

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Advances in Remote Sensing 2016年第3期5卷 157-167页

作者： Xin Qiao Ahmad Khalilian Jose O. Payero Joe Mari Maja Charles V. Privette Young J. Han Department of Agricultural and Environmental Sciences Clemson University Clemson SC USA edisto rec Clemson University Blackville SC USA

Accurate soil moisture content measurements are vital to precision irrigation management. Remote sensing using the microwave spectrum (such as GPS signals) has been used for measuring large area soil moisture contents. In our previous work, we estimated surface soil moisture contents for bare soil using a GPS Delay Mapping receiver (DMR) developed by NASA. However, the effect of vegetation was not considered in these studies. Hence the objectives of this study were to: 1) investigate the feasibility of using DMR to determine soil moisture content in cotton production fields;2) evaluate the attenuation effect of vegetation (cotton) on reflected GPS signal. Field experiments were conducted during the 2013 and 2014 growing seasons in South Carolina. GPS antennas were mounted at three heights (1.6, 2.7, and 4.2 m) over cotton fields to measure reflected GPS signals (DMR readings). DMR readings, soil core samples, and plant measurements were collected about once a week and attenuation effect of plant canopy was calculated. Results showed that DMR was able to detect soil moisture changes within one week after precipitation events that were larger than 25 mm per day. However, the DMR readings were poorly correlated with soil volumetric water content during dry periods. Attenuation effect of plant canopy was not significant. For irrigation purpose, the results suggested that the sensitivity of reflected GPS signals to soil moisture changes needed to be further studied before this technology could be utilized for irrigation scheduling in cotton production. Refinement of this technology will expand the use of advanced remote sensing technology for site-specific and timely irrigation scheduling. This would eliminate the need to install moisture sensors in production fields, which can interfere with farming operations and increase production costs.

关键词： Remote Sensing GPS Soil Volumetric Water Content Cotton Irrigation

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Relationship of Soil Moisture and Reflected GPS Signal Strength

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Advances in Remote Sensing 2016年第1期5卷 18-27页

作者： Charles V. Privette III Ahmad Khalilian William Bridges Stephen Katzberg Omar Torres Young J. Han Joe Mari Maja Xin Qiao Department of Agricultural and Environmental Sciences Clemson University Clemson SC USA edisto rec Clemson University Blackville SC USA Mathematical Sciences Department Clemson University Clemson SC USA South Carolina State University Orangeburg SC USA NASA Langley Research Center NASA Hampton VA USA

Many agricultural fields across the country have a high degree of variability in soil type and water holding capacity that affects irrigation management. One way to overcome problems associated with the field variability for improving irrigation management is to utilize a site-specific irrigation system. This system applies water to match the needs of individual management zones within a field. A real-time continuous soil moisture measurement is essential for the success of site-specific irrigation systems. recently the National Aeronautics and Space Administration (NASA) developed sensor technology that records the global positioning system (GPS) signal reflected from the surface of Earth, which estimates the dielectric properties of soil and can be used to estimate soil moisture contents. The overall objective of this study was to determine the feasibility of utilizing GPS-based technology developed by NASA for soil moisture measurements and to determine the influence of soil type, soil compaction, and ground cover on the measurements. The results showed strong positive correlations between soil moisture and reflected signals. Other factors (soil compaction and soil type), were not significantly related to reflectivity and did not significantly change the relationship between reflectivity and soil moisture contents. In addition, ground cover (rye crop) did not significantly reduce reflectivity. Therefore, this system could be used as a real-time and continuous nonintrusive soil moisture sensor for site-specific irrigation scheduling and watershed management.

关键词： Remote Sensing Soil Moisture GPS Reflectivity Site-Specific Irrigation

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