Mahdi Al-Kaisi

Effect of Nitrogen Fertilizer Application on Growing Season Soil Carbon Dioxide Emission in a Corn–Soybean Rotation

Nitrogen application can have a significant effect on soil carbon (C) pools, plant biomass production, and microbial biomass C processing. The focus of this study was to investigate the short-term effect of N fertilization on soil CO(2) emission and microbial biomass C. The study was conducted from 2001 to 2003 at four field sites in Iowa representing major soil associations and with a corn (Zea mays L.)-soybean (Glycine max L. Merr.) rotation. The experimental design was a randomized complete block with four replications of four N rates (0, 90, 180, and 225 kg ha(-1)). In the corn year, season-long cumulative soil CO(2) emission was greatest with the zero N application. There was no effect of N applied in the prior year on CO(2) emission in the soybean year, except at one of three sites, where greater applied N decreased CO(2) emission. Soil microbial biomass C (MBC) and net mineralization in soil collected during the corn year was not significantly increased with increase in N rate in two out of three sites. At all sites, soil CO(2) emission from aerobically incubated soil showed a more consistent declining trend with increase in N rate than found in the field. Nitrogen fertilization of corn reduced the soil CO(2) emission rate and seasonal cumulative loss in two out of three sites, and increased MBC at only one site with the highest N rate. Nitrogen application resulted in a reduction of both emission rate and season-long cumulative emission of CO(2)-C from soil.

Drought impact on crop production and the soil environment: 2012 experiences from Iowa

Enormous challenges were presented by the 2012 drought. Poor water availability and high temperatures resulted in significant stress during critical phases of corn (Zea mays L.) and soybean (Glycine max L.) development. These stress factors lead to management challenges with insects, diseases, and reduced nutrient availability and uptake by plants. The drought triggered soil changes, particularly in conventional tillage systems, such as increased fracturing, crusting, and deterioration of soil structure and aggregation. All this reinforced the need for soil conservation planning, especially its necessary role in buffering against unpredictable conditions and the impacts of dry and wet events on production and soil quality. In 2011, the USDAs National Drought Mitigation Center reported that 43% of Iowa experienced moderate-drought conditions and nearly 10% experienced severe-drought conditions. In 2012, 100% of Iowa experienced severe-drought conditions, while 65% experienced extreme-drought conditions by October. This article addresses several effects of drought on soil and crop production and lessons learned that will help develop appropriate drought mitigation strategies for future soil and crop management practices. The 2012 drought created unfavorable soil conditions for plant development and growth and changes in soil structure in many areas in the Midwest. These changes in soil structure included fracturing…

Transpiration and evapotranspiration from maize as related to leaf area index

Abstract Evapotranspiration and transpiration from maize ( Zea mays L.) were measured with precision weighing lysimeters in 1983 and 1984. Climatic parameters were measured to calculate potential evapotranspiration, while leaf area index was measured twice weekly. Crop coefficients were determined from daily values of evapotranspiration (or transpiration)/potential evapotranspiration. Non-linear models were tested and showed that 72–86% of the variation in crop coefficient for evapotranspiration could be described knowing leaf area index. Model testing with transpiration showed that 90–95% of the variation in crop coefficient could be described knowing leaf area index.

Soil Carbon Dynamics and Carbon Budget of Newly Reconstructed Tall-grass Prairies in South Central Iowa

In addition to their aesthetic and environmental qualities, reconstructed prairies can act as C sinks and potentially offset rising atmospheric CO(2) concentration. The objective of this study was to quantify C budget components of newly established prairies on previously cultivated land. Net ecosystem production (NEP) was estimated using a C budgeting approach that assessed SOC content, soil surface CO(2)-C emission, and above- and belowground plant biomass. Study was conducted in southern Iowa, in 2005 to 2007. Results show that differences between sites for potential total C input were primarily due to root biomass contributions, which ranged from 0.8 to 5.4 Mg C ha(-1). Average potential aboveground biomass C input was 2.7 Mg C ha(-1) in 2006 and 5.5 Mg C ha(-1) in 2007. Total soil CO(2)-C emissions from heterotrophic respiration increased as prairie age increased from 2.9 to 4.0 Mg C ha(-1) and 3.1 to 4.7 Mg C ha(-1) in 2006 and 2007, respectively. Determination of NEP showed that the 1998 and 2003 reconstructed prairie sites had the greatest potential for soil C sequestration at 4.1 and 4.4 Mg C ha(-1). Increases in SOC content were only observed in the youngest established prairie site (2003) and the no-till site in 2003 at 2.1 and 2.6 Mg C ha(-1) yr(-1), respectively. Declines of SOC sequestration rates occurred when potential C equilibrium was reached (R(h) = NPP) within 10 yr since prairie establishment.

Landscape position effect on selected soil physical properties of reconstructed prairies in southcentral Iowa

Changes in land use and alteration of the ecosystem can significantly affect soil physical, chemical, and biological properties. In this study, changes in soil organic carbon (SOC), root biomass, bulk density (ρb), water stable aggregates (WSA), and infiltration rates were examined in reconstructed prairies varying in age and landscape position. The objective of the study was to determine the potential of landscape position effect on these selected soil properties in reconstructed prairies. Findings show that SOC increased as years since prairie establishment increased and had a positive correlation with infiltration rate and WSA. The opposite was true for ρb, where it decreased as prairie age increased and negatively correlated with SOC. However, the effects of SOC and ρb on infiltration rates varied by landscape slope position and age of prairie establishment. Root biomass, SOC, and WSA had decreased, while ρb increased at the midslope compared to the summit and toe-slope positions resulting in lower infiltration rates. Although the summit and the toe-slope positions had similar soil properties, infiltration rates were much greater in the toe-slope position. This was ascribed to the toe-slope positions superior WSA, due to greater SOC concentrations. In general, this study shows that over time, increases in SOC did promote aggregate formation and lower ρb, creating more permeable soil surfaces in these reconstructed prairies. However, better soil conservation practices that reduce soil surface water runoff in the midslope in particular are needed during the first few years of prairie establishment.

Evaluation of irrigation scheduling program and spring wheat yield response in southwestern Colorado

Abstract Effective irrigation scheduling to manage water for spring wheat (Triticum aestivum L.) in southwestern Colorado was investigated under variable water applications. This study was conducted (1) to determine the effects of varying rates of water replacement (0ET, 0.33ET, 0.67ET, 10ET, and 1.33ET) on spring wheat grain yield, dry matter yield, root water uptake, and water use efficiency, (2) to develop local crop coefficients, and (3) to evaluate the irrigation scheduling program called ‘SCHED’ that had been used in the area. Daily weather data was used to calculate reference ET using the Penman equation. Crop ET was predicted by using the irrigation scheduling program, ‘SCHED’. Both grain yield and dry matter increased significantly with the increase in water application rates, up to LOET application rate. Crop coefficients estimated at various water application rates were greater than the values used in the irrigation scheduling program. Total water use efficiency (TWUE) and irrigation water use efficiency (IWUE) for grain yield were considerably greater at 0.33ET than for other rates, whereas TWUE and IWUE for dry matter yield followed the order 0.33ET > LOET > 0.67ET > 1.33ET > 0ET.

Cost-effectiveness and cost-benefit analysis of conservation management practices for sediment reduction in an Iowa agricultural watershed

Soil erosion from agricultural lands can be reduced by adoption of conservation management practices. The objectives of this study were to investigate the effectiveness and cost-benefit of conservation management practices on sediment reduction under a corn—soybean rotation. The experimental site was 6.4 ha (15.8 ac) and located within the Four Mile Creek watershed in eastern Iowa. Management practices consisted of tillage with a mold-board plow with a row cropped system of corn and soybeans. Annual sediment yield from this site was estimated using the Water Erosion Prediction Project (WEPP) model for three tillage systems (chisel plow, disk tillage, and no-tillage) as well as three conservation structures (grassed waterways, filter strips, and terraces). The WEPP model was validated using five-year (1976 to 1980) field-measured sediment yield and surface runoff data. Without supplemental conservation measures, predicted sediment yield was 22.5, 17.7, and 3.3 t ha−1 y−1 (10.0, 7.9, and 1.5 tn ac−1 yr−1) from chisel plow, disk tillage, and no-tillage, respectively. Supplemental conservation measures had the most impact on sediment yield reduction when used in conjunction with chisel plow management and the smallest impact with the no-tillage system. The value of lost soil resulting from soil erosion ranged between

Impact of soil erosion on soil organic carbon stocks

10.9 and

Examining the paired comparison method approach for determining soil organic carbon sequestration rates

137.3 ha−1 y−1 (

Landscape position and age of reconstructed prairies effect on soil organic carbon sequestration rate and aggregate associated carbon

4.4 and