Jerry L. Hatfield

Intercepted photosynthetically active radiation estimated by spectral reflectance

Abstract Interception of photosynthetically active radiation (PAR) was evaluated relative to greenness and normalized difference [MSS (7 − 5)/(7 + 5)] for five planting dates of wheat for 1978–1979 and 1979–1980 at Phoenix, Arizona. Intercepted PAR was calculated from leaf area index and stage of growth. Linear relationships were found with greenness and normalized difference with separate relationships describing growth and senescence of the crop. Normalized difference was significantly better than greenness for all planting dates. For the leaf area growth portion of the season the relation between PAR interception and normalized difference was the same over years and planting dates. For the leaf senescence phase the relationships showed more variability due to the lack of data on light interception in sparse and senescing canopies. Normalized difference could be used to estimate PAR interception throughout a growing season.

Data quality checking for single station meteorological databases

In the past decade individual and networks of automated meteorological stations have been installed throughout the United States and many other countries. For a variety of reasons, the data collected are being archived in databases; however, quality control/quality assurance procedures, when employed, vary greatly. As a start to possible standardization, screening rules for hourly and daily data values are proposed for quality checking micrometeorological data from individual base stations that record solar irradiance (SI), precipitation (P), barometric pressure (Pb), vapor pressure (e), wind speed (u2), wind direction (θ2), air temperature (Ta), and three soil temperatures (Ts0, Ts1, and Ts2). Three types of screening rules are considered: (1) high/low range limits (LIM), (2) rate-of-change limits (ROC), (3) continuous no-observed-change with time limits (NOC). Daily data from historical meteorological records for Ames, IA (30 years) and Treynor, IA (26 years) were available for developing climatic based dynamic data screening rules. Otherwise, instrument specifications and theoretical models were used to develop screening rules for the remaining measurements. Hourly and daily data from well maintained, automated weather stations at Walnut Creek, IA (9 months) and Treynor, IA (1 year) were used to evaluate and refine the screening rules. Daily data are not flagged often. The most common flag, on either time-scale, was on vapor pressure when its value exceeded the 95% relative humidity calibration limit of the sensor. Hourly SI often exceeded a computed extraterrestrial radiation value, particularly at sunset. Rule 1 (LIM) is mainly invoked via observations outside the sensor ranges; rule 2 (ROC) flags abrupt changes; rule 3 (NOC) flags unusually steady periods in the data stream. When used as part of a total field operation and data processing system, these rules improve the data quality and may help with data exploration.

Value of Using Different Vegetative Indices to Quantify Agricultural Crop Characteristics at Different Growth Stages under Varying Management Practices

The paper investigates the value of using distinct vegetation indices to quantify and characterize agricultural crop characteristics at different growth stages. Research was conducted on four crops (corn, soybean, wheat, and canola) over eight years grown under different tillage practices and nitrogen management practices that varied rate and timing. Six different vegetation indices were found most useful, depending on crop phenology and management practices: (a) simple ratio for biomass, (b) NDVI for intercepted PAR, (c) SAVI for early stages of LAI, (d) EVI for later stages of LAI, (e) CIgreen for leaf chlorophyll, (f) NPCI for chlorophyll during later stages, and (g) PSRI to quantify plant senescence. There were differences among varieties of corn and soybean for the vegetation indices during the growing season and these differences were a function of growth stage and vegetative index. These results clearly imply the need to use multiple vegetation indices to best capture agricultural crop characteristics.

Greenhouse Gas Emissions from Two Soils Receiving Nitrogen Fertilizer and Swine Manure Slurry

The interactive effects of soil texture and type of N fertility (i.e., manure vs. commercial N fertilizer) on N(2)O and CH(4) emissions have not been well established. This study was conducted to assess the impact of soil type and N fertility on greenhouse gas fluxes (N(2)O, CH(4), and CO(2)) from the soil surface. The soils used were a sandy loam (789 g kg(-1) sand and 138 g kg(-1) clay) and a clay soil (216 g kg(-1) sand, and 415 g kg(-1) clay). Chamber experiments were conducted using plastic buckets as the experimental units. The treatments applied to each soil type were: (i) control (no added N), (ii) urea-ammonium nitrate (UAN), and (iii) liquid swine manure slurry. Greenhouse gas fluxes were measured over 8 weeks. Within the UAN and swine manure treatments both N(2)O and CH(4) emissions were greater in the sandy loam than in the clay soil. In the sandy loam soil N(2)O emissions were significantly different among all N treatments, but in the clay soil only the manure treatment had significantly higher N(2)O emissions. It is thought that the major differences between the two soils controlling both N(2)O and CH(4) emissions were cation exchange capacity (CEC) and percent water-filled pore space (%WFPS). We speculate that the higher CEC in the clay soil reduced N availability through increased adsorption of NH(4)(+) compared to the sandy loam soil. In addition the higher average %WFPS in the sandy loam may have favored higher denitrification and CH(4) production than in the clay soil.

Abatement of Ammonia and Hydrogen Sulfide Emissions from a Swine Lagoon Using a Polymer Biocover

ABSTRACT The purpose of this research was to determine the efficiency of a polymer biocover for the abatement of H2S and NH3 emissions from an east-central Missouri swine lagoon with a total surface area of 7800 m2. The flux rate of NH3, H2S, and CH4 was monitored continuously from two adjacent, circular (d = 66 m) control and treatment plots using a nonintrusive, micrometeorological method during three independent sampling periods that ranged between 52 and 149 hr. Abatement rates were observed to undergo a temporal acclimation event in which NH3 abatement efficiency improved from 17 to 54% (p = <0.0001 to 0.0005) and H2S abatement efficiency improved from 23 to 58% (p < 0.0001) over a 3-month period. The increase in abatement efficiency for NH3 and H2S over the sampling period was correlated with the development of a stable anaerobic floc layer on the bottom surface of the biocover that reduced mass transfer of NH3 and H2S across the surface. Analysis of methanogenesis activity showed that the biocover enhanced the rate of anaerobic digestion by 25% when compared with the control. The biocover-enhanced anaerobic digestion process was shown to represent an effective mechanism to counteract the accumulation of methanogenic substrates in the biocovered lagoon.

EPIC Modeling of Soil Organic Carbon Sequestration in Croplands of Iowa

Depending on management, soil organic carbon (SOC) is a potential source or sink for atmospheric CO(2). We used the EPIC model to study impacts of soil and crop management on SOC in corn (Zea mays L.) and soybean (Glycine max L. Merr.) croplands of Iowa. The National Agricultural Statistics Service crops classification maps were used to identify corn-soybean areas. Soil properties were obtained from a combination of SSURGO and STATSGO databases. Daily weather variables were obtained from first order meteorological stations in Iowa and neighboring states. Data on crop management, fertilizer application and tillage were obtained from publicly available databases maintained by the NRCS, USDA-Economic Research Service (ERS), and Conservation Technology Information Center. The EPIC model accurately simulated state averages of crop yields during 1970-2005 (R(2) = 0.87). Simulated SOC explained 75% of the variation in measured SOC. With current trends in conservation tillage adoption, total stock of SOC (0-20 cm) is predicted to reach 506 Tg by 2019, representing an increase of 28 Tg with respect to 1980. In contrast, when the whole soil profile was considered, EPIC estimated a decrease of SOC stocks with time, from 1835 Tg in 1980 to 1771 Tg in 2019. Hence, soil depth considered for calculations is an important factor that needs further investigation. Soil organic C sequestration rates (0-20 cm) were estimated at 0.50 to 0.63 Mg ha(-1) yr(-1) depending on climate and soil conditions. Overall, combining land use maps with EPIC proved valid for predicting impacts of management practices on SOC. However, more data on spatial and temporal variation in SOC are needed to improve model calibration and validation.

Climate-smart agriculture global research agenda: scientific basis for action

BackgroundClimate-smart agriculture (CSA) addresses the challenge of meeting the growing demand for food, fibre and fuel, despite the changing climate and fewer opportunities for agricultural expansion on additional lands. CSA focuses on contributing to economic development, poverty reduction and food security; maintaining and enhancing the productivity and resilience of natural and agricultural ecosystem functions, thus building natural capital; and reducing trade-offs involved in meeting these goals. Current gaps in knowledge, work within CSA, and agendas for interdisciplinary research and science-based actions identified at the 2013 Global Science Conference on Climate-Smart Agriculture (Davis, CA, USA) are described here within three themes: (1) farm and food systems, (2) landscape and regional issues and (3) institutional and policy aspects. The first two themes comprise crop physiology and genetics, mitigation and adaptation for livestock and agriculture, barriers to adoption of CSA practices, climate risk management and energy and biofuels (theme 1); and modelling adaptation and uncertainty, achieving multifunctionality, food and fishery systems, forest biodiversity and ecosystem services, rural migration from climate change and metrics (theme 2). Theme 3 comprises designing research that bridges disciplines, integrating stakeholder input to directly link science, action and governance.OutcomesIn addition to interdisciplinary research among these themes, imperatives include developing (1) models that include adaptation and transformation at either the farm or landscape level; (2) capacity approaches to examine multifunctional solutions for agronomic, ecological and socioeconomic challenges; (3) scenarios that are validated by direct evidence and metrics to support behaviours that foster resilience and natural capital; (4) reductions in the risk that can present formidable barriers for farmers during adoption of new technology and practices; and (5) an understanding of how climate affects the rural labour force, land tenure and cultural integrity, and thus the stability of food production. Effective work in CSA will involve stakeholders, address governance issues, examine uncertainties, incorporate social benefits with technological change, and establish climate finance within a green development framework. Here, the socioecological approach is intended to reduce development controversies associated with CSA and to identify technologies, policies and approaches leading to sustainable food production and consumption patterns in a changing climate.

Comparison of DAYCENT-Simulated and Measured Nitrous Oxide Emissions from a Corn Field

Accurate assessment of N(2)O emission from soil requires continuous year-round and spatially extensive monitoring or the use of simulation that accurately and precisely predict N(2)O fluxes based on climatic, soil, and agricultural system input data. DAYCENT is an ecosystem model that simulates, among other processes, N(2)O emissions from soils. The purpose of the study was to compare N(2)O fluxes predicted by the DAYCENT model to measured N(2)O fluxes from an experimental corn field in central Iowa. Soil water content temperature and inorganic N, simulated by DAYCENT were compared to measured values of these variables. Field N(2)O emissions were measured using four replicated automated chambers at 6-h intervals, from day of year (DOY) 42 through DOY 254 of 2006. We observed that DAYCENT generally accurately predicted soil temperature, with the exception of winter when predicted temperatures tended to be lower than measured values. Volumetric water contents predicted by DAYCENT were generally lower than measured values during most of the experimental period. Daily N(2)O emissions simulated by DAYCENT were significantly correlated to field measured fluxes; however, time series analyses indicate that the simulated fluxes were out of phase with the measured fluxes. Cumulative N(2)O emission calculated from the simulations (3.29 kg N(2)O-N ha(-1)) was in range of the measured cumulative N(2)O emission (4.26 +/- 1.09 kg N(2)O-N ha(-1)).

The Nitrogen Cycle, Historical Perspective, and Current and Potential Future Concerns

This chapter deals with the nitrogen cycle, historical perspective, and current and potential future concerns. Nitrogen (N) along with carbon is the most complex and crucial of the elements essential for life. Nitrogen is the most widely utilized plant nutrient in fertilizers and is a major component of animal manures. Nitrogen compounds also have been recognized for their many potential adverse impacts on the environment and health. The chapter explores that research during the period 1880 to 1910 revealed many basic reactions of the N cycle and set the stage for five decades of vigorous and detailed N cycle studies. The use of a nitrification test to measure soil fertility was proposed, tested, and abandoned. Furthermore, N fertilizer consumption rapidly increased. Total N from manures are relatively small compared to fertilizer sources; the move to concentrated animal feeding operations has resulted in high N outputs in local areas. Nitrogen fertility research continued on a site and crop specific basis, but less attention was paid to environmental issues. In recycling of issues, N is now gaining renewedattention as new environmental problems have come to the forefront and old issues have resurfaced. This chapter concludes that perhaps as a society wide spread dissemination of knowledge, open and informed discussion at world forums, and consensus on appropriate actions is called for. Technical solutions are the domain of the scientist, but such solutions must fit the world needs for a sustainable future.

Inconsistencies in net radiation estimates from use of several models of instruments in a desert environment

Abstract Studies of surface energy and water balance generally require an accurate estimate of net radiation and its spatial distribution. A project quantifying both short term and seasonal water use of shrub and grass vegetation in the Jornada Experimental Range in New Mexico prompted a study to compare net radiation observations using two types of net radiometers currently being used in research. A set of 12 REBS net radiometers were compared with each other and one Swissteco, over wet and dry surfaces in an arid landscape under clear skies. The set of REBS exhibited significant differences in output over both surfaces. However, they could be cross calibrated to yield values within 10xa0Wxa0m −2 , on average. There was also a significant bias between the REBS and Swissteco over a dry surface, but not over a wet one. The two makes of instrument could be made to agree under the dry conditions by using regression or autoregression techniques. However, the resulting equations would induce bias for the wet surface condition. Thus, it is not possible to cross calibrate these two makes of radiometer over the range of environmental conditions observed. This result indicates that determination of spatial distribution of net radiation over a variable surface should be made with identical instruments which have been cross calibrated. The need still exists for development of a radiometer and calibration procedures which will produce accurate and consistent measurements over a range of surface conditions.