Cropping and livestock systems: Manure and soil quality

Agriculture across the Midwest was founded on the integration of crop and livestock systems. This integration was based on the utilization of crop production for animal feed and utilization of the manure as the nutrient sources for the crops. This same integration of components of the agricultural system exists today but we no longer view these components as an integrated puzzle and tend to consider crop and livestock production as separate systems. The Midwest is one of the most intensive agricultural systems leading in corn and soybean production, dairy, hog and poultry production and can serve as an example of the value of returning to viewing agriculture as an integrated system

Special Issue from the 4\u3csup\u3eth\u3c/sup\u3e USDA Greenhouse Gas Symposium

Greenhouse gases emitted from agricultural and forest systems continue to be a topic of interest because of their potential role in the global climate and the potential monetary return in the form of carbon credits from the adoption of mitigation strategies. There has been a history of excellent conferences as part of the USDA Greenhouse Gas Symposium effort sponsored by the USDA Global Change office with cooperation from different agencies and organizations. Rice (2006) described the contribution of agricultural and forest systems to greenhouse gas emissions and how these inventories serve as a baseline for how we regard the potential impacts of these systems. The continuing increase in worldwide concentrations of CO2 has implications for plant growth and climate feedbacks. Understanding the implications of these changes lead to the theme of the 4th USDA Greenhouse Gas Symposium “Positioning Agriculture and Forestry to meet the Challenges of Climate Change” at the conference held in Baltimore, Maryland from 6–8 Feb. 2007

Climate Change Impacts on Corn Phenology and Productivity

Global climate is changing and will impact future production of all food and feed crops. Corn is no exception and to ensure a future supply we must begin to understand how climate impacts both the phenological development of corn and the productivity. Temperature and precipitation are the two climate factors that will have a major benefit on corn phenology and productivity. The warming climate will accelerate the phenological development because the number of thermal units required for leaf appearance is relatively constant in the vegetative stage. Productivity of corn is reduced when extreme temperature events occur during pollination and is further exaggerated when there are water deficits at pollination. During the grain-filling period, warm temperatures above the upper threshold cause a reduction in yield. Model estimates suggest that for every 1°C increase in temperature there is nearly a 10% yield reduction. To meet world demand, new adaptation practices are needed to provide water to the growing crop and avoid extreme temperature events during the growing season. Climate change will continue to affect corn production and understanding these effects will help determine where future production areas exist and innovative adaptation practices to benefit yield stability could be utilized

Temperature extremes: Effect on plant growth and development

AbstractTemperature is a primary factor affecting the rate of plant development. Warmer temperatures expected with climate change and the potential for more extreme temperature events will impact plant productivity. Pollination is one of the most sensitive phenological stages to temperature extremes across all species and during this developmental stage temperature extremes would greatly affect production. Few adaptation strategies are available to cope with temperature extremes at this developmental stage other than to select for plants which shed pollen during the cooler periods of the day or are indeterminate so flowering occurs over a longer period of the growing season. In controlled environment studies, warm temperatures increased the rate of phenological development; however, there was no effect on leaf area or vegetative biomass compared to normal temperatures. The major impact of warmer temperatures was during the reproductive stage of development and in all cases grain yield in maize was significantly reduced by as much as 80−90% from a normal temperature regime. Temperature effects are increased by water deficits and excess soil water demonstrating that understanding the interaction of temperature and water will be needed to develop more effective adaptation strategies to offset the impacts of greater temperature extreme events associated with a changing climate

Canopy Resistance as Affected by Soil and Meteorological Factors in Potato

Precision irrigation requires a method of quantifying the crop water status or root zone depletion of water to determine when and how much water to apply to the soil. Changes in canopy resistance (rc) and canopy temperatures have the potential of being used as a crop water status indicator for irrigation management. A study was conducted on potato (Solanum tuberosum L.) grown in northern Egypt at Shibin El-Kom on an alluvial loamy soil for winter (20 Sept. 2001 through 20 Jan. 2002) and spring (1 Feb. 2002 through 20 May 2002) seasons to determine if rc derived from energy balance and plant parameters could be used to determine the onset of water stress and the amount of water required to refill the soil profile. Diurnal rc was determined for well-watered conditions and achieved minimum values of 20 and 10 s m-1 at noontime during winter and spring periods, environmenrespectively. A power relationship of -0.86 for well-watered conditions was developed between rc and net radiation (Rn) at various plant growth stages. In deficit soil water conditions, rc increased linearly with decreasing available soil water (ASW), with a change in potato rc of 0.75 and 0.39 s m-1 per percentage ASW for 1 and 2 MJ m-2 h-1 of Rn at midgrowth, respectively. A ratio of actual/potential canopy resistance (rc/rcp) was derived to normalize the meteorological differences between growing seasons. This ratio was 2.5 when 50% of ASW was removed and can be used as a parameter to determine the need for irrigations using weather factors and canopy temperature. Canopy resistance increased linearly with increasing soil solution salinity, electrical conductivity, when the soil solution was above the threshold soil salinity value. A ratio of rc/rcp was found to normalize the effects of different environments across saline and water deficit conditions

Effects of Tillage System on Corn and Soybean Production

Producers are concerned about the differences among tillage systems and how these affect corn and soybean production and profitability. The variation among modern tillage systems often causes confusion in terms of what factor is affected within the production system. There is also interest in being able to compare the effects of the different tillage systems across a wide range of soils and climates within Iowa. A study funded by IDALS in cooperation with HSTL is conducting a series of studies across Iowa at 10 sites to compare four different tillage systems on 1) changes in soil properties; 2) crop performance and economic return; 3) the response of local producers in each region to the study results; and 4) the potential behavioral change in producers in each region in terms of changing tillage practices that will increase profit and improve environmental quality

Water-Use Efficiency: Advances and Challenges in a Changing Climate

Water use efficiency (WUE) is defined as the amount of carbon assimilated as biomass or grain produced per unit of water used by the crop. One of the primary questions being asked is how plants will respond to a changing climate with changes in temperature, precipitation, and carbon dioxide (CO2) that affect their WUE At the leaf level, increasing CO2 increases WUE until the leaf is exposed to temperatures exceeded the optimum for growth (i.e., heat stress) and then WUE begins to decline. Leaves subjected to water deficits (i.e., drought stress) show varying responses in WUE. The response of WUE at the leaf level is directly related to the physiological processes controlling the gradients of CO2 and H2O, e.g., leaf:air vapor pressure deficits, between the leaf and air surrounding the leaf. There a variety of methods available to screen genetic material for enhanced WUE under scenarios of climate change. When we extend from the leaf to the canopy, then the dynamics of crop water use and biomass accumulation have to consider soil water evaporation rate, transpiration from the leaves, and the growth pattern of the crop. Enhancing WUE at the canopy level can be achieved by adopting practices that reduce the soil water evaporation component and divert more water into transpiration which can be through crop residue management, mulching, row spacing, and irrigation. Climate change will affect plant growth, but we have opportunities to enhance WUE through crop selection and cultural practices to offset the impact of a changing climate