C. Alan Rotz

Alfalfa Drying Model for the Field Environment

ABSTRACT FIELD drying rates for alfalfa between 80 and 20% moisture content (wet basis) were measured along with environmental conditions from 1977 to 1984 at East Lansing, MI. Linear correlation was used to determine environmental factors which most influenced drying rate and nonlinear regression was used to develop an empirical model of drying rate as a function of the environment. Drying rate was most heavily influenced by solar insolation. Other factors which influenced drying included dry bulb temperature or vapor pressure deficit, soil moisture content, and swath density. Drying was also faster on the day in which the crop was mowed. When chemical conditioning was used, drying rate was influenced by the application rate of the chemical solution. Following the chemical treatment, swath density and the first day of drying had more influence on drying rate. Models relating these factors to drying rate provided a coefficient of determination of 0.64 when validated by comparing predicted and actual drying rate.

Nitrogen–climate interactions in US agriculture

Agriculture in the United States (US) cycles large quantities of nitrogen (N) to produce food, fuel, and fiber and is a major source of excess reactive nitrogen (Nr) in the environment. Nitrogen lost from cropping systems and animal operations moves to waterways, groundwater, and the atmosphere. Changes in climate and climate variability may further affect the ability of agricultural systems to conserve N. The N that escapes affects climate directly through the emissions of nitrous oxide (N2O), and indirectly through the loss of nitrate (NO3−), nitrogen oxides (NOx) and ammonia to downstream and downwind ecosystems that then emit some of the N received as N2O and NOx. Emissions of NOx lead to the formation of tropospheric ozone, a greenhouse gas that can also harm crops directly. There are many opportunities to mitigate the impact of agricultural N on climate and the impact of climate on agricultural N. Some are available today; many need further research; and all await effective incentives to become adopted. Research needs can be grouped into four major categories: (1) an improved understanding of agricultural N cycle responses to changing climate; (2) a systems-level understanding of important crop and animal systems sufficient to identify key interactions and feedbacks; (3) the further development and testing of quantitative models capable of predicting N-climate interactions with confidence across a wide variety of crop-soil-climate combinations; and (4) socioecological research to better understand the incentives necessary to achieve meaningful deployment of realistic solutions.

Ammonia emission model for whole farm evaluation of dairy production systems.

Ammonia (NH) emissions vary considerably among farms as influenced by climate and management. Because emission measurement is difficult and expensive, process-based models provide an alternative for estimating whole farm emissions. A model that simulates the processes of NH formation, speciation, aqueous-gas partitioning, and mass transfer was developed and incorporated in a whole farm simulation model (the Integrated Farm System Model). Farm sources included manure on the floor of the housing facility, manure in storage (if used), field-applied manure, and deposits on pasture (if grazing is used). In a comprehensive evaluation of the model, simulated daily, seasonal, and annual emissions compared well with data measured over 2 yr for five free stall barns and two manure storages on dairy farms in the eastern United States. In a further comparison with published data, simulated and measured barn emissions were similar over differing barn designs, protein feeding levels, and seasons of the year. Simulated emissions from manure storage were also highly correlated with published emission data across locations, seasons, and different storage covers. For field applied manure, the range in simulated annual emissions normally bounded reported mean values for different manure dry matter contents and application methods. Emissions from pastures measured in northern Europe across seasons and fertilization levels were also represented well by the model. After this evaluation, simulations of a representative dairy farm in Pennsylvania illustrated the effects of animal housing and manure management on whole farm emissions and their interactions with greenhouse gas emissions, nitrate leaching, production costs, and farm profitability.

Economics of Chemically Conditioned Alfalfa on Michigan Dairy Farms

ABSTRACT ALFALFA drying models for standard and chemical conditioning were integrated with a whole-farm model of the dairy-forage system. Simulation was used to evaluate benefits and costs of chemical conditioning over 25 years on representative Michigan dairy farms. Conditioning with potassium carbonate can be economical in hay production, but uneconomical in haylage production. An economically-optimum application rate of 500 L/ha was determined for first cutting with optimum rates of 200 and 300 L/ha on second and third cuttings. Use of a heavy swath during field drying caused the treatment to be less effective and uneconomical.

Potassium sorbate reduces production of ethanol and 2 esters in corn silage

The objective of this work was to evaluate the effects of biological and chemical silage additives on the production of volatile organic compounds (VOC; methanol, ethanol, 1-propanol, methyl acetate, and ethyl acetate) within corn silage. Recent work has shown that silage VOC can contribute to poor air quality and reduce feed intake. Silage additives may reduce VOC production in silage by inhibiting the activity of bacteria or yeasts that produce them. We produced corn silage in 18.9-L bucket silos using the following treatments: (1) control (distilled water); (2) Lactobacillus buchneri 40788, with 400,000 cfu/g of wet forage; (3) Lactobacillus plantarum MTD1, with 100,000 cfu/g; (4) a commercial buffered propionic acid-based preservative (68% propionic acid, containing ammonium and sodium propionate and acetic, benzoic, and sorbic acids) at a concentration of 1 g/kg of wet forage (0.1%); (5) a low dose of potassium sorbate at a concentration of 91 mg/kg of wet forage (0.0091%); (6) a high dose of potassium sorbate at a concentration of 1g/kg of wet forage (0.1%); and (7) a mixture of L. plantarum MTD1 (100,000 cfu/g) and a low dose of potassium sorbate (91 mg/kg). Volatile organic compound concentrations within silage were measured after ensiling and sample storage using a headspace gas chromatography method. The high dose of potassium sorbate was the only treatment that inhibited the production of multiple VOC. Compared with the control response, it reduced ethanol by 58%, ethyl acetate by 46%, and methyl acetate by 24%, but did not clearly affect production of methanol or 1-propanol. The effect of this additive on ethanol production was consistent with results from a small number of earlier studies. A low dose of this additive does not appear to be effective. Although it did reduce methanol production by 24%, it increased ethanol production by more than 2-fold and did not reduce the ethyl acetate concentration. All other treatments increased ethanol production at least 2-fold relative to the control, and L. buchneri addition also increased the 1-propanol concentration to approximately 1% of dry matter. No effects of any treatments on fiber fractions or protein were observed. However, L. buchneri addition resulted in slightly more ammonia compared with the control. If these results hold under different conditions, a high dose of potassium sorbate will be an effective treatment for reducing VOC production in and emission from silage. Regulations aimed at reducing VOC emission could be ineffective or even increase emission if they promote silage additives without recognition of different types of additives.

Greenhouse Gas Emissions from Dairy Farms

The reduction of greenhouse gas emissions is becoming more important world-wide. Although research suggests that farmland can serve as a sink for carbon, agriculture is also an important source of emissions. As a sector, agriculture is reported to be the greatest contributor of nitrous oxide and the third greatest contributor of methane in the U.S. Thus, strategies must be designed to reduce or eliminate net emissions of greenhouse gases. Before these strategies can be developed, we must first understand typical emission ranges from each source at the farm level in order to focus on the processes with the greatest emissions. Sources on dairy farms include soil, growing crops, feed storage, animals, and manure in animal housing facilities, during storage, and following field application. Other countries, particularly in Europe, have quantified emission ranges, although these data are less established within the U.S. An extensive literature review was conducted to determine the major processes contributing to greenhouse gas emissions from dairy farms and to quantify typical emission levels. From these typical levels, emissions were estimated for a representative dairy farm. This review and farm analysis will help direct modeling efforts by determining the important physical processes that drive emissions of carbon dioxide, methane, and nitrous oxide in dairy production. The review also expands the knowledge base of researchers, farm planners, and policymakers as they work to develop and maintain sustainable farming systems.

Process-based Modeling of Ammonia Emission from Beef Cattle Feedyards with the Integrated Farm Systems Model

Ammonia (NH) volatilization from manure in beef cattle feedyards results in loss of agronomically important nitrogen (N) and potentially leads to overfertilization and acidification of aquatic and terrestrial ecosystems. In addition, NH is involved in the formation of atmospheric fine particulate matter (PM), which can affect human health. Process-based models have been developed to estimate NH emissions from various livestock production systems; however, little work has been conducted to assess their accuracy for large, open-lot beef cattle feedyards. This work describes the extension of an existing process-based model, the Integrated Farm Systems Model (IFSM), to include simulation of N dynamics in this type of system. To evaluate the model, IFSM-simulated daily per capita NH emission rates were compared with emissions data collected from two commercial feedyards in the Texas High Plains from 2007 to 2009. Model predictions were in good agreement with observations and were sensitive to variations in air temperature and dietary crude protein concentration. Predicted mean daily NH emission rates for the two feedyards had 71 to 81% agreement with observations. In addition, IFSM estimates of annual feedyard emissions were within 11 to 24% of observations, whereas a constant emission factor currently in use by the USEPA underestimated feedyard emissions by as much as 79%. The results from this study indicate that IFSM can quantify average feedyard NH emissions, assist with emissions reporting, provide accurate information for legislators and policymakers, investigate methods to mitigate NH losses, and evaluate the effects of specific management practices on farm nutrient balances.

Nitrous Oxide Emissions from Open-Lot Cattle Feedyards: A Review

Nitrous oxide (NO) emissions from concentrated animal feeding operations, including cattle feedyards, have become an important research topic. However, there are limitations to current measurement techniques, uncertainty in the magnitude of feedyard NO fluxes, and a lack of effective mitigation methods. The objective of this review was to assess NO emission from cattle feedyards, including comparison of measured and modeled emission rates, discussion of measurement methods, and evaluation of mitigation options. Published annual per capita flux rates for beef cattle feedyards and open-lot dairies were highly variable and ranged from 0.002 to 4.3 kg NO animal yr. On an area basis, published emission rates ranged from 0 to 41 mg NO m h. From these studies and Intergovernmental Panel on Climate Change emission factors, calculated daily per capita NO fluxes averaged 18 ± 10 g NO animal d (range, 0.04-67 g NO animal d). This variation was due to inconsistency in measurement techniques as well as irregularity in NO production and emission attributable to management, animal diet, and environmental conditions. Based on this review, it is clear that the magnitude and dynamics of NO emissions from open-lot cattle systems are not well understood. Further research is required to quantify feedyard NO fluxes and develop cost-effective mitigation methods.

Conversion from Corn to Grassland Provides Economic and Environmental Benefits to a Maryland Beef Farm

Beef producers must consider management strategies and technologies for reducing potential adverse environmental effects of their farms while maintaining or improving profit. One choice is between using perennial grassland or corn as the primary crop on the farm for feed production. Perennial grassland production systems are generally regarded as more favorable due to reduced nutrient losses to the environment and potential human health benefits through improvements in meat fatty acid composition. Simulation of an Angus cattle-producing farm of 325 acres in northeastern Maryland illustrated that the conversion of the farm from a corn and permanent pasture system to all perennial grassland with the use of more intensive rotational grazing has provided both environmental and economic benefits. Simulated nitrogen loss through ammonia volatilization was increased 21%, but nitrate leaching was reduced 56%, denitrification loss was reduced 50%, and surface runoff loss of P was reduced 75%. This conversion also increased the annual net return of the farm by

Dual-fueling turbocharged diesels with ethanol

18,800 by eliminating the greater machinery, fuel, seed, fertilizer, and chemical costs incurred in corn production.