Agricultural Cropland Research Articles

Weather Forecasts as a Control Input for Water Table Management in Coastal Areas

ABSTRACT FOUR water table management methods were compared in computer simulations of a controlled-drainage and subirrigation system using soils and climate conditions of the Mississippi Delta region. No significant difference in the predicted relative corn yield was obtained among the four management methods when the operation for each method was adjusted to maximize yield. However, stopping subirrigation pumping whenever the rainfall probability index (RPI) exceeded 55% reduced pumping requirements for three of the methods 12 to 21% compared to the continuous subirrigation method. The optimal management of soil-water for agricultural cropland in humid, coastal areas of the U.S. often involves complex daily control of the water table because of the erratic spatial and temporal distribution of rainfall. Periods of excess and deficit soil-water conditions are common within the same growing season. Thus, water management requires both controllable drainage and irrigation facilities. A water table management system popular in the humid region, especially in the southern coastal plains, uses a subsurface draintube system for both controlled-drainage and subirrigation. Controlled-drainage permits storage of rainfall and irrigation water in the soil profile below the depth of an overflow pipe at the drain outlet. Free'' drainage to the full depth of the drainline is often needed during periods of extended or heavy rainfall to reduce the duration of excess water in root zone. During subirrigation, the water level at the drain outlet is maintained just below the overflow pipe by pumping from an external source. A sump-type structure for controlling the water level at the drain outlet for a water table management system is illustrated in Fig. 1. The check-valve, activated by a double-float, allows fast subsurface drainage during peak flow events, functioning like the two-stage weir described by Fouss, et al. (1987b). It is often necessary to pump from a sump in level and low lying topography of the coastal plains, where subsurface drainage by gravity flow is not possible. Water table management with this type of system has a high potential for achieving maximum crop production and water use efficiency if properly controlled to compensate for changes in weather conditions. The timing of changes needed in controlled-drainage and subirrigation to manage optimally the water table depth is a major problem for farmers, especially in coastal areas with fine textured soils. In the Mississippi Delta frequent occurrences of rainfall can cause large variations in water table depth because of the small, 3 to 8%, drainable soil porosity. Results from computer simulation of four management methods for water table control are presented for soils and climate conditions of the Mississippi Delta. The primary research objective was to determine the best operational parameters that efficiently utilized rainfall during the growing season without creating periods of severe excess soil-water conditions, and which minimized the need for pumping drainage and subirrigation water. Special attention was given to the potential use of rainfall probability information from the daily weather forecast as a system control input to minimize subirrigation pumping.

Winter Browse Availability and Use by White-Tailed Deer in Southeastern Indiana

Browse availability and use by white-tailed deer (Odocoileus virginianus) in southeastern Indiana were studied during winter 1978-79. Significant positive regressions were found between browse use and availability for the entire study area (habitat ignored) and within mature forests and second-growth woods. These data support the hypothesis that deer forage nonselectively in winter. No relationship was found between use and availability in oldfields. Browse use was lower in oldfields than in mature forests and secondgrowth woods, but the availability of browse did not differ between habitats. J. WILDL. MANAGE. 49(1): 120-124 White-tailed deer have evolved numerous physiological and behavioral adaptations for survival during the thermal and nutritional stresses of winter. Conservation of energy is achieved through lower metabolic rates, reduced activity, restricted home-range size, increased shelter-seeking behavior, and greater insulating properties of winter pelage (Mautz 1978, Moen 1978). In addition, insulation and energy are provided by fat reserves deposited during summer and autumn when food resource availability and quality are favorable (Short 1975, Mautz 1978). Winter forage is frequently poorly digested (Robbins and Moen 1975, Short 1975, Mautz et al. 1976), but is necessary to slow the catabolism of finite fat deposits (Mautz 1978). Nudds (1980) suggested that northern deer should adopt a generalist foraging strategy during winter in response to low food availability and quality. With such a strategy, relative use of food types is approximately equal to relative availability. He argued that energy acquisition should become the critical factor for survival and optimization of the diet for other nutrients should be relaxed. Data from Wetzel et al. (1975) were reanalyzed by Nudds (1980) and supported the hypothesis of diet generalization in winter. We examined the availability and use of woody browse by white-tailed deer in southeastern Indiana during winter (Dec-Mar). We tested the hypothesis that browse use is positively related to availability. We thank T. D. Nudds and L. D. Vangilder for reviewing earlier drafts of this manuscript. STUDY AREA The 2.5-km2 study area encompassed the Brookville Ecology Research Center and adjacent agricultural and state park lands south of Liberty, Union County, Indiana. A diversity of habitats was present, including upland and bottomland mature forest, second-growth woods, oldfields, and cropland. Topography varied with steep slopes rising from river bottoms to level upland. Dominant features of the landscape included the man-made impoundments of Brookville and Whitewater lakes. Population density of white-tailed deer in the study area was estimated at ~14 individuals/km2 (LaGory 1979). Mature forest occupied 50% of the study area and consisted of mixed deciduous hardwoods. Major canopy species in upland sites were oak (Quercus), white ash (Fraxinus americana), sugar maple (Acer saccharum), and American be ch (Fagus grandifolia). American sycamore (Platanus occidentalis), boxelder maple (A. negundo), and eastern cottonwood (Populus deltoides) were common canopy species in bottomland forests. Abandoned agricultural cropland and pasture existed as oldfields (26% of the study area) and second-growth woods (7%). Herbaceous plants included goldenrod (Solidago), aster (Aster), milkweed (Asclepias), wild carrot (Daucus carota), ragweed (Ambrosia), and several native and domesticated grasses. Shrubs and young trees common to oldfields and second-growth woods included osage-orange (Maclura pomifera), common honeylocust (Gleditsia triacanthos), wild cherry (Prunus), dogwood (Cornus), elm (Ulmus), white

Nutrient Dynamics in an Agricultural Watershed: Observations on the Role of A Riparian Forest

Nutrient (C, N, and P) concentration changes were measured in surface runoff and shallow groundwater as they moved through a small agricultural (cropland) watershed located in Maryland. During the study period (March 1981 to March 1982), dramatic changes in water—borne nutrient loads occurred in the riparian forest of the watershed. From surface runoff waters that had transited °50 m of riparian forest, an estimated 4.1 Mg of particulates, 11 kg of particulate organic—N, 0.83 kg of ammonium—N, 2.7 kg of nitrate—N and 3.0 kg of total particulate—P per ha of riparian forest were removed during the study year. In addition, an estimated removal of 45 kg°ha—1°yr—1 of nitrate N occurred in subsurface flow as it moved through the riparian zone. Nutrient uptake rates for the cropland are riparian forest were estimated. These systems were then compared with respect to their pathways of nutrient flow and ability to retain nutrients. The cropland appeared to retain fewer nutrients than the riparian forest and is thought to incur the majority of its nutrient losses in harvested crop. The dominant pathway of total—N loss from the riparian forest seemed to be subsurface flux. Total phosphorus loss from the riparian forest appeared almost evenly divided between surface and subsurface losses. Nutrient removals in the riparian forest and thought to be of ecological significance to receiving waters and indicate that coupling natural systems and managed habitats within a watershed may reduce diffuse—source pollution.

Structure of Benthic Macroinvertebrate Communities in a Midwestern Plains Stream

Functional group structure of benthic macroinvertebrate communities was compared among three distinct reaches of the Redwood River, a plains stream in southwestern Minnesota. Deciduous leaf-fall comprised the allochthonous organic input to the upstream site, typical of a woodland stream; at the middle site, fine particulate organic matter, derived from soils in agricultural croplands, comprised the main allochthonous import; and at the lower site, soil-derived particulates and zooplankton from an impoundment comprised the main organic import. Mineral fine particulates, primarily silt, entered the stream during most of the year. The upstream site was most similar to other woodland streams in its functional invertebrate structure, with shredders and collectors both well represented. In the middle and downstream communities, collectors were quantitatively most important, with gatherers in depositional reaches and filterers in erosional reaches. Instability of physical habitat, influenced by heavy siltation from agricultural croplands appeared to favor a community of generalist collectors.

Mineralization of Nitrogen in Sewage Sludges

AbstractMineralization of organic N is one of the principle factors governing the annual amount of sewage sludge applied to agricultural cropland. The mineralization of sludge organic N was studied in a Fincastle silt loam soil treated with 24 sewage sludges obtained from sewage treatment plants in several regions of the United States. The mineralization of sludge organic N was determined during a 16‐week incubation by analysis of inorganic N in (i) leachates from soil‐sludge‐sand mixtures and (ii) subsamples of unleached soil‐sludge mixtures. The nonleached procedure gave slightly higher estimates of mineralizable N in most sludges (average of 17 and 16% N mineralized by nonleached and leached procedures, respectively). The approximate amounts of mineralizable N in sludges expressed as a percentage of organic N were: raw and primary, 25%; waste‐activated, 40%; anaerobically digested, 15%; and composted, 8%. Inorganic N released from sludges by autoclaving in 0.01M CaCl2 or extracting with H2SO4 + KMnO4 was not highly correlated with N mineralization. Sludge organic N content was a reasonable predictor of mineralization of sludge N added to soils. The following regression equation was found to describe the mineralization of sludge organic N in soil: % of added sludge N mineralized = 6.37 × % sludge organic N + 4.63 (r = 0.77). To calculate the appropriate sludge application rates for agronomic crops, the percentage of sludge N mineralized during the initial cropping season should be related either to the process used for sludge treatment or to the concentration of organic N in the sludge.

Quantitative determination of 1,2-dibromo-3-chloropropane in whole rat blood and drinking water by gas chromatography

1,2-Dibromo-3-chloropropane (DBCP) in an amber-colored liquid that has been used as a soil fumigant for nematodes since 1957 in agricultural cropland. Formulations containing DBCP have been primarily sold under the trademarks Fumazone (Dow Chemical, Midland, MI, U.S.A.) and Nemagon (Shell, THe Hague, The Netherlands). Recent reports have associated exposure to DBCP with disruption of spermatogenesis and azoospermia or oligospermia in male workers. Tests on laboratory animals have indicated that DBCP has an adverse effect on spermatogenesis and leads to testicular atrophy. In support of DBCP studies in animals, an analytical method was developed to determine low-level concentrations of DBCP in whole blood. Previous analytical methods for DBCP in blood required extensive sample preparation and steam distillation which limits the number of analysis per time period. This paper describes a simple gas chromatographic-electron-capture detection (GC-ECD) method that is both specific and sensitive to DBCP blood levels at concentrations as low as 2.28 x 10(-1) ng/ml DBCP. In addition, a quantitative analytical method was developed to measure levels of DBCP in drinking water which parallels the method in blood.

An Inventory of Particulate Emissions from Open Sources

Open sources are those stationary sources of air pollution too great in extent to be controlled through enclosure or ducting. Open sources of atmospheric particles include: wind erosion, tilling, and prescribed burning of agricultural cropland; surface mining and wind erosion of tailings piles; vehicular travel on both paved and unpaved roads; construction site activity; and forest fires. It is estimated that in 1976 the total open source emissions of particles in the U.S. amounted to over 580 × 106 ton. These estimates indicate that emissions from the two largest open source classes, travel on unpaved roads and agricultural wind erosion, accounted for 86% of this total. The open source emissions in ten states (AZ, CA, KS, MN, MT, NM, ND, OH, SD, TX) contributed 6 2% of the national emissions for 1976.

Sediment Damage and Farm Production Costs: A Multiple-Objective Analysis

When considering many environmental problems, society is faced with decisions involving multiple objectives and with problems in valuing environmental impacts. This study illustrates a multiple goal approach applicable to land and water resource project evaluations. The approach explicitly confronts the problem of valuing the environmental impacts of sediment and determines the implications of placing alternative relative weights-, on the components of the objective function. The results quantify the tradeoffs between production cost and sediment damage. Agricultural cropland sediment is recognized as the largest nonpoint water pollutant by volume in the United States.' Direct costs associated with sediment include lost reservoir capacity, increased channel and reservoir dredging, increased water treatment, reduced recreational activities, and increased flood damages. Indirect costs arise from the associated transport of agricultural chemicals into waterways. In addition, continued erosion reduces current as well as future productive capacity of agricultural lands. The increasing awareness of the impacts of sediment on environmental quality is leading society to include these impacts in analyses of land and water resource projects. This awareness is illustrated in legislation such as the Iowa Conservancy Law, which extends the authority of the conservancy district commissioners to classify land on the basis of its erodibility, to estab

An Analysis of Time-Budgeting By Roe Deer (Capreol Us Capreol Us) in an Agricultural Area

AbstractAn analysis of time-budgeting by Capreolus capreolus in an agricultural area is presented in two sections: the first concerns resting behavior, the second, time-budgeting within the active state. Of primary interest were comparisons between age-/sex-classes over seasons. Data were collected by direct observation of a free-ranging roe deer population with ca 50% of the animals individually marked. The study site consisted of ca 200 ha of agricultural cropland with a small wooded area on one end and interspersed tree-rows. An ethogram was constructed to enable the recording of behavioral samples on tape; these were later transcribed onto computer cards and the data were analyzed by computer using non-parametric and parametric tests. Roe deer spent ca 55% of the day lying (and ruminating) during the Winter. Differences between age-/sex-classes over the year were related to differential behavior towards protective cover, rather than differential energy requirements. Therefore, age-/sex-differences in time-budgeting were sought within the active period. It was found that ca 90% of the time spent on foot was devoted to 4 non-overlapping ethogram elements - orienting, walking, moving (searching), and feeding - and one collective element - social behavior. These 5 elements were subjected to more detailed statistical analyses, and indeed, significant age-/sex-class, as well as seasonal differences were found. The differences elucidated were often in agreement with predictions made from models or theories based on energetic considerations. This does not reduce the importance of recently hypothesized nutrient-balancing tasks, but it did demonstrate that time-variable energy demands were still operative in herbivores. Several results indicated that females follow more conservative strategies than males: they tended to reduce costs when faced with higher energy demands, whereas males tended to increase energy intake.

A Spatial Equilibrium Model for Evaluating Alternative Policies for Controlling Sediment from Agriculture

A model for evaluating alternative sediment control policies in agriculture is formulated such that changes in the production of agricultural commodities among and within 105 agricultural production areas can be analyzed. The model combines the elements of spatial economic equilibrium with physical and technical aspects of cropland agriculture. Five alternative sediment control policies as might be formulated by national environment planning agencies are analyzed. The analysis of the alternative policies do not give a definitive solution to sediment water quality problems but rather provide significant information on technical, regional and cost distributions of agricultural production to help decision makers formulate national sediment control policies.

Income Effects of Reducing Agricultural Pollution

The value and quantity of agricultural commodity production in various regions of the United States determines farmers' income in each region. Many farmers, businessmen, policy makers and administrators are concerned with the problem of change in farm income resulting from water quality restraints placed on cropland agriculture. This study evaluates the income change from a series of hypothetical national water quality policies by examining the changes in national and regional gross farm income. Long-run changes in total national income of controlling water pollution from farmland by soil loss restraints are relatively small, as aggregate gross income increases by four to six percent depending on the level of control studied.The changes in regional gross farm income are more extreme since various regions of the country, including the southern states, are affected differently by potential water quality control. This study utilizes a national modeling system to examine these variables and reports an analysis of potential changes in gross farm income caused by environmental restraints placed on agriculture. Environmental goals analyzed are national soil conservation ones, with implications for national and regional farm incomes.

Markov Intertemporal Land Use Simulation Model

The simulation model discussed in this paper evolved from problems encountered in estimating future United States cropland availability as part of the OBERS agricultural projection system. Available literature describing land use changes indicate that land resource economists have not been concerned with projecting future patterns of land use implied by historic observations.Some research has involved selection of optimum cropping patterns for agricultural cropland subject to alternative flood plain management policies. However, the broader application of such models between sectors (agriculture, industrial, urban, etc.), in the main, has been ignored. Because of “historical bias” there has not been a concerted effort to develop analytical capabilities for use in evaluating the future implications of alternative regional and/or national policies designed to alter trends in land use shifts.

EFFECTS OF INTERBASIN TRANSFERS UPON WATER MANAGEMENT ALTERNATIVES IN CENTRAL UTAH1

ABSTRACT. Most of Utah's rapid population and industrial expansion is taking place along the western base of the Wasatch Mountains, with consequent increases in water demand. As a part of Utah's “Developing a State Water Plan,” a foundation investigation of the Utah Lake drainage area, which is at the Southern end of the Wasatch Front, was completed which delineated the quantity and quality of the water resources, present water uses, and opportunities for further water conservation. To prepare water budgets, land use data was collected to delineate all areas using water in excess of normal precipitation, which includes agricultural croplands, phreatophytes, open water surfaces, industrial areas, and urban areas. The water budgets were prepared for the time base 1931‐1960, but adjusted to physical conditions existing in 1960.The Initial Phase of the Bonneville Unit of the Central Utah Project is presently under construction, with costs expected to exceed 300 million dollars. The principal feature of this project is the exportation of waters from the Colorado River Basin into the Utah Lake drainage area (Great Basin). This importation provides a large number of alternatives for allocation, reallocation of present supplies, and exportation. The possible effects of the Central Utah Project for realizing some of the above alternatives is delineated. Fortunately, the features of this project allow a wide latitude for water management in Utah, thereby facilitating its corporation into a “State Water Plan.”

RESULTS OF THE MOUNTAIN HOME RAINFALL INTERCEPTION AND INFILTRATION PROJECT IN BLACK WATTLE, 1953/54

Summary Interception of rainfall by a mature plantation canopy is estimated at 15–20 per cent over the whole year. It varies between 40 per cent with light rains and 13 per cent with heavy. Net rainfall in the plantation is due, over the whole year, 86 per cent to throughfall and 14 per cent to stemflow. During light rain and drizzle as opposed to storms, stemflow forms a much higher proportion (up to 23 per cent). Condensation from mist never led to a higher precipitation than recorded in the open. If it occurred in the plantation during light rain its presence was masked by the interception. Throughfall under grass cover was found to be much less than under the plantation. It averaged 67 per cent for the whole year with grass burnt in spring and was from 53 to 58 per cent under mature grass. Stemflow of grasses could not be accurately measured but was evidently of considerable magnitude. Interception by grass cover is thought to be very small. It is unlikely to exceed 10 per cent over a whole year and may well be much less. Six per cent of the total annual rainfall was lost by run-off in the veld and 7.7 per cent in the plantation. Run-off in the plantation is higher in spring due to resistance to wetting of the floor, but in summer and autumn does not materially exceed that in the veld. Wattle plantations may therefore be a less efficient watershed cover than ungrazed natural grassland from the point of view of net infiltration, since the higher interception and run-off reduce net rainfall reaching the soil. The difference is not however of any great magnitude and importance, and when the run-off and erosion losses from heavily grazed grasslands and agricultural croplands are considered, it fades into insignificance. It would appear that the difference could be to a large extent reduced or eliminated in plantations where slash-piles have been placed along the contour and left to rot down.