Maximize Crop Production Research Articles

Assessing nonpoint source pollution in the vadose zone

Sustainable agriculture is viewed as the only viable means of meeting the food demands of the world's projected population of 11 billion by the year 2050. Sustainable agriculture is predicated on a delicate balance of maximizing crop productivity and maintaining economic stability while minimizing the use of finite natural resources and avoiding the detrimental environmental impacts of associated nonpoint source (NPS) pollutants. NPS pollutants include pesticides, fertilizers, trace elements, salts, sediments, etc., and are known to be carcinogenic, mutagenic, or teratogenic. NPS pollutants threaten sustainable agriculture and are recognized as the single greatest threat to surface and subsurface drinking water resources.

Eco-rating System for Optimizing Pesticide Use at Farm Level. Part 1: Theory and Development

Abstract A computer-based decision support system is described which aims to encourage and enhance sound environmental management within agriculture. Part of the system focuses on the management of pesticides on the farm, and can help to ensure that the farmer adopts practices which maximize crop production and profitability without jeopardizing the environment. The approach taken looks at all aspects of farm pesticide use including crop applications, storage and waste disposal and the use of non-crop pesticides. As a whole, the system can act as a informal environmental management system. An ecorating is derived by comparing actual farm practices with what is perceived to be best practice for the site, to provide a measure of environmental performance. The first time the method is used, these indices act as benchmarks against which the success of future improvements can be judged. The system has three modes of operation. An “assessment mode” seeks to identify strengths and weakness in practices and regulatory compliance and to provide guidance on areas where improvements could be made. In support of this, a second mode known as the “technical system” allows the user to explore “what–if” scenarios in order to identify site-specific best practice and aims to provide answers to the issues raised in the assessement mode. The third mode is a fully integrated hypertext information system containing a range of context-sensitively mapped text on agriculture and the environment which can be used on a stand-alone basis or accessed from any part of the software system.

Development of Alternative Weed Management Strategies

Concerns in the public and agricultural sectors about agricultural practices have led many weed scientists and producers to consider alternative weed management strategies. Weed management practices have been influenced greatly by the availability of selective herbicides for major crops. The impact of herbicides has been so dominating that weed science is often perceived to be the science of herbicides rather than the science of weeds. The general public and many agricultural producers are searching for alternatives to herbicide-intensive weed management practices. A shift away from dependence on herbicides is complicated by a poor understanding of weed biology and ecology and the availability of few alternative weed control tactics. Education and research efforts have to focus on the application of existing knowledge as well as the development of new fundamental knowledge. Reductions in herbicide use can be attained within the framework of existing management systems. However, given the poor understanding of weeds and lack of control options, new approaches to weed management are needed. Weed scientists have to play a central role in the development of new cropping systems to avoid continuation of reactive approaches to weed control. Research Question Concerns over current practices have lead many weed scientists and crop producers to seek alternative strategies for weed control. The goal of these strategies is to develop systems that provide producers with more options for weed control and reduce dependence on tillage and herbicides, thus minimizing the environmental, biological, economic, and societal impacts of controlling weeds. Herbicides have been a valuable tool and have provided benefits to the farm and urban communities. However, weed control has to be viewed as a more integrated science. Refocusing away from overdependance on a single technology (herbicides) will require greater understanding of biological systems than we currently possess. Literature Summary Weed management is in transition from strict reliance on control of existing problems to placing greater emphasis on prevention of propagule production, reduction of weed emergence in a crop, and minimizing weed competition with the crop. Weed management emphasizes integration of techniques to manage or anticipate problems rather than solving them after they are present. Weed management does not eliminate the need for control nor does it advocate that our best control techniques be abandoned. Its goal is to maximize crop production where appropriate and optimize grower profit by integrating preventative techniques, scientific knowledge, and management skills. Weed control is achieved by physical, chemical, or biological disturbance. All forms of disturbance exert selection pressure and result in the survival and proliferation of the best adapted plants. Several decades of use of modem production practices have not eliminated weeds, but have greatly changed the population dynamics of weed communities. In order to develop new cropping and weed management systems, the impacts of agricultural practices on weeds must be better understood and anticipated. Applied Questions Are there practices that growers can implement immediately to reduce herbicide use? Yes. The use of mechanical control operations alone or in combination with herbicide banded over the crop row or reduced rates of herbicide can reduce herbicide use and maintain weed control. Field scouting and record keeping may also lead to more efficient use of herbicides. Weed thresholds and decision aid models may also lead to reduced use. What type of research is needed to develop alternative weed management systems that go beyond current cropping systems? A better understanding of weed biology and ecology is the key. This information will aid in the development of site-specific management systems and in the redesign of cropping systems. There is also potential for new control practices such as biological control, allelopathic plants, smother plant systems, or more competitive crop cultivars.

Improving Nitrogen Management of Vegetable Crops Through Intensive Monitoring

The production of cool-season vegetable crops in California's coastal valleys is characterized by high N input (typically 200–300 kg·ha–1 per crop), with two crops per year the norm. N. removal in harvested biomass seldom exceeds 100 kg·ha–1, suggesting a high degree of inefficiency in N management. A project was conducted on a commercial farm in Santa Maria to document the utility of intensive monitoring of soil and plant N status on improving N management. Eight fields were monitored through successive cropping cycles. Slow-release N fertilizer was applied preplant at 110–250 kg·ha–1 in subplots in each field to provide a reference of known N sufficiency against which to compare field productivity; these reference plots also received the same in-season fertilizer N applied in the balance of the field. N monitoring techniques included: in situ and controlled-environment soil incubation to estimate net N mineralization, soil NO3-N analysis by a “quick test” technique using colormetric test strips, and petiole sap analysis by NO3-N selective electrode. It was consistently demonstrated that, for lettuce, cauliflower, and broccoli, maximum crop productivity was obtained with seasonal N applications 50–100 kg N/ha less than the industry norm and that fertilizer cost savings more than offset the cost of crop and soil monitoring.

Engineering systems to enhance irrigation performance

The desirable irrigation system applies water at a rate that allows all water to infiltrate and distributes the water in space and time to match crop requirements in each parcel of the field. Various types of irrigation systems and management strategies have been developed in attempts to achieve the “desired” system. Our objective is to review various methods of enhancing irrigation performance. Although the “desired” system has not been attained, considerable improvements have been made based upon selection and management technologies which generate profits within the constraints of environmental prudence. Each irrigation system has inherent opportunities for enhancing irrigation performance. Like-wise, each has limitations in achieving maximum crop productivity per unit of applied water. Methods to improve the performance or surface irrigation can be grouped into those that increase the uniformity of water intake, reduce runoff losses, or decrease spatial variability. Two surface irrigation systems that enhance performance are surge-flow and level-basin. The uniformity and efficiency of sprinkler systems can be enhanced by computer-based design procedures and, in some cases, by applying low-energy, precision application concepts. Advantages of microirrigation are less surface area wetted, which minimizes evaporation and weed growth, and improved application uniformity which is specifically designed into the distribution network. An appropriate management strategy is necessary to attain the potential of an irrigation system engineered to match crop water requirements, and soil and environmental conditions. The best irrigation method applies the amount of water desired at the appropriate time while providing for leaching requirements, agronomic operations, and environmental considerations. With enhanced engineering and computer capabilities and improved knowledge of the soil-plant-water continuum, irrigators will adopt “prescription” irrigation. Prescription systems apply precisely the prescribed amounts of water, nutrients, and pesticides to match the production capacity of each parcel of land.

DRIP IRRIGATION OF VEGETABLE CROPS IN THE SOUTHWEST

The use of drip irrigation in the production of vegetable crops has expanded rapidly in the Southwest in the last decade. The factors contributing to this conversion are: a) water availability and cost, b) improved design and production of drip irrigation products which has dramatically improved performance and reliability, c) reduced cost of drip irrigation in relation to other crop production costs, and d) development of integrated management practices which maximize crop productivity and system performance. Regionally, more than 30,000 ha of vegetable crops are produced annually using drip irrigation, the majority of which is in California; major commodities are tomato, pepper, melons and salad crops. Many different types of drip installations have been evaluated. The trend in new installations is toward buried systems in semipermanent beds, with multiple crops being produced before system renovation. Specialized management practices are evolving which make such systems highly efficient.

Review of water table depth planning for a multi objective water management system

In this paper, the concepts for planning and design of drainage depth will be reviewed in relation to the different requirements for maximizing crop production. The relationships of the drainage depth with other design parameters and their interdependency will be discussed. Reference will be made to the cost, cost/benefit ratio and economic returns of drainage systems with respect to the drainage depth. Some applications and practices in different countries will be highlighted.

Similarities among Test Sites Based on Cultivar Performance in the Hard Red Winter Wheat Region

Maximizing crop productivity requires effective selection and targeting of cultivars for appropriate production areas. Understanding similarities in cultivar response among test sites and underlying production zones within a crop production region is important for breeders to effectively choose test sites and interpret test data. Thirty years of wheat (Triticum aestivum L.) yield data from the Southern and Northern Regional Performance Nurseries (SRPN and NRPN, respectively) were analyzed in order to determine similarities among test sites and production zones in the Great Plains hard red winter wheat growing area. Correlations of cultivar yields among locations each year were averaged and used as a basis for principal factor analysis. Six intraregional production zones were identified in the SRPN, with six factors accounting for 55% of the variability in the location correlation dependence structure. Four of the factors essentially divided the central plains region on north‐south, east‐west axes, representing the south‐central plains, north‐central plains, southern high plains, and central high plains areas. Five production zones were identified in the NRPN, with five factors accounting for 55% of the variation in the location correlation dependence structure. Factor analysis was used to further classify sites within three of the larger production zones in the SRPN and two in the NRPN. Sixteen smaller production areas were identified within these major zones. Elucidation of intraregional cultivar production zones should facilitate more precise targeting of wheat breeding and evaluation efforts.

Bonanza Club: 35 Years of Maximum Crop Production and Extension Education in Southwestern Kansas

The Bonanza Club was created by Grant County, Kansas, agricultural leaders in 1955, when rapid regional change was occurring. The Bonanza Club is one component of a county extension crops program. Its goal is to provide timely and useful information regarding new and successful agronomic practices applied by producers and to encourage the use of those that prove beneficial. Each year selected fields are enrolled by producers and cropping practices are documented. During a fall tour of enrolled fields, producers describe their production practices and local seed dealers, extension agents, and specialists discuss cultivars and practices. After fall harvest, worksheets are compiled into a report booklet, and an awards banquet is held to recognize participants and achievements. The report booklet is distributed at the awards banquet and to other interested extension and agribusiness personnel. As of 1989, 117 participants with 1200 crop entries representing 34 425 ha have been enrolled. The annual budget, $2200, is provided by local businesses. The fall crop tour and awards banquet have been well-attended. Bonanza Club grain yields of irrigated grain sorghum [Sorghum bicolor (L.) Moench.], corn (Zea mays L.), and wheat (Triticum aestivum L.) have averaged above county averages by 30, 12, and 41%, respectively. The Bonanza Club has been an excellent source of information for local producers and changing cropping practices have been documented in southwestern Kansas.

Modeling Yields from Rainfall and Supplemental Irrigation

Frequently, the area of good soils suitable for irrigation far exceeds that for which adequate water is available for maximum crop production. Decisions and/or policies are often required relative to how much land should be irrigated with limited water supplies or the level of deficit irrigation desirable. The use of crop‐yield models provides a tool for determining how best to combine benefits from rainfall and irrigation. Some developments are described that facilitate the modeling of crop yields. A method that requires only temperature measurements for reliable estimates of potential evapotranspiration facilitates modeling at many locations where more complete climatic data are not available. A weather simulation procedure that provides good results without local calibration and requires only monthly climatic input makes it possible to develop a worldwide climatic data base for use with the existing crop‐yield models that otherwise require the availability of daily climatic data. Estimated probable rel...

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.

Agricultural concepts of roots: from morphogenetic to functional equilibrium between root and shoot growth.

Over the past century, emphasis has changed towards water and nutrient uptake by root system ('functional equilibrium') from relations between root and shoot growth, ('morphogenetic equilibrium'). Separate optima for root growth and shoot growth can often be distinguished. Relatively small root systems can suffice for maximum crop production, provided the supply of water and nutrients is plentiful. Deep tillage or water-table lowering, intended to increase rooting depth, can be counterproductive for plant growth. Larger root systems may, however, withstand rapidly changing environmental conditions better, and may increase nutrient use efficiency or reduce nutrient loss. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Policy structures and crop productivity in third world countries

Deciding what should be done in the crop-production sector is a policy issue and a public and management responsibility. Entrusted with that responsibility, governments formulate policies which should ensure maximum crop productivity. The impact of policies and policy structures on crop productivity, and the role of policy makers, administrators and scientists in research and development systems are the subjects of this paper. Observations are made on the role played by government policies in the generation, diffusion and application of crop-production technology and a brief discussion is presented of issues of public and international policies and crop productivity.

Residual Effects of N Fertilization on Dryland Spring Wheat in the Northern Plains. II. Fate of Fertilizer N1

AbstractResidual effects of fertilizer application on the fate of fertilizer N applied to crops in semiarid regions are largely unknown. Objectives of this study were to provide information on the recovery of fertilizer N during the fertilization and residual periods and to develop an N balance sheet for a continuous spring wheat (Triticum aestivum L.) cropping system.Ammonium nitrate was applied to spring wheat at 0 to 540 kg N/ha rate either (i) all in 1 year, (ii) one‐third in each of 3 years, or (iii) one‐sixth in each of 6 years to evaluate the availability and fate of fertilizer N in a dryland cropping system. Only grain was removed during harvest, and straw was plowed under each spring. Grain N uptake accounted for 31 to 46% of the total fertilizer N applied at 270 and 540 kg N/ha rate for various timing frequency. Fertilizer N uptake in straw and root biomass at the end of the experiment averaged 5 and 26 kg/ha, respectively. Movement of NO3‐N below the 90‐ cm depth (leaching) was detected for the 270 kg N/ha treatment, whether this total amount was applied all in 1 year, or 90 kg N/ha was applied in each for 3 years. However, with an annual application of 45 kg N/ha for 6 continuous years very little leaching of NO3‐N occurred. The amount of fertilizer N that moved beyond the root zone was greater at 540 than at 270 kg N/ha. Leaching of fertilizer N below 90 cm accounted for 4 to 37% of the total fertilizer applied, with greatest leaching occurring For the 1‐year treatment and least for the 6‐year treatment. Loss of N by runoff was negligible. The percent fertilizer N accounted for [(total fertilizer accountable ÷ total fertilizer applied) × 100] averaged 62, 64, and 66 for 1, 3, and 6‐year treatments, respectively. Unaccounted for fertilizer N possibly consisted of that portion of fertilizer N immobilized in soil organic fractions resistant to decomposition and that lost by volatilization. Results showed that if the N rate is adequate for maximum crop production, fertilizer efficiency is greatest when N is applied annually rather than at higher rates less frequently.

Residual Effects of N Fertilization on Dryland Spring Wheat in the Northern Plains. I. Wheat Yield and Water Use1

AbstractData are frequently lacking to quantify the residual effects of fertilizer applications on soil nutrient availability, especially in regions of limited rainfall. Therefore, the effects of fertilizer N on yields of continuous dryland spring wheat (Triticum aestivum L.) grown on Typic haploboroll soil were determined in a field study at Mandan, North Dakota. Rates up to 540 kg N/ha applied either (i) all in 1 year, (ii) one‐third of the total rate in each of 3 years, or (iii) one‐sixth of the total rate each year for 6 years of the experiment. Average dry matter (1967–1972) at different stages of growth and average grain yields were increased significantly by increased N rate, but only dry matter at tillering was significantly affected by rate × timing interaction. With 270 and 540 kg N/ha applied in only the first year, residual effects significantly increased grain production in 4 of the following 5 years. At total rates of 135 kg N/ha or above, total grain yield for the 6‐year period was greatest for the 6‐year fertilization treatment and least for the 1‐year treatment. Average annual grain yields for the 540 kg N/ha rates were 1,700, 1,660 and 1,880 kg/ha for the 1, 3, and 6‐year treatments, respectively, and 1,050 kg/ha for the zero‐N treatment. Weight of grain produced per kilogram of fertilizer N applied usually decreased as N rate increased. At the 135 kg N/ha rate or higher, grain production per unit of fertilizer applied was greatest for the 6‐year treatments (annual fertilization). Root weight and development in the 6th year were related to the availability of soil N as reflected by fertilizer treatment.Total water use was significantly influenced by N rate or frequency of fertilization in only 2 of the 6 years. Water use efficiency (WUE) increased as N rate increased, irrespective of fertilization frequency. Highest WUE was obtained by 6‐year fertilization treatment and for most treatments WUE decreased .when annual fertilization ceased. Although residual N derived from previous fertilization seems to be very important for subsequent crop production, availability of N from residual sources was not sufficient to maintain maximum crop production over a number of years.

Responses of Greenhouse‐grown Cannabis sativa L. to Nitrogen, Phosphorus, and Potassium1

AbstractGrowers of illegal Cannabis sativa L. use various cultural practices to maximize crop production. The objective of this study was to evaluate the morphological and biochemical responses of greenhouse grown C. sativa to soil incorporated N, P, and K as they reflect the geographical origin of Cannabis derivatives. Fertilizers were blended with Ap horizon soil from a Gilpin silt loam before placement in 12‐cm pots. NH4NO3‐N was applied at 0, 25, and 125 ppm. Phosphorus and K from super‐phosphate and KCI, respectively, were applied at 0, 50, and 150 ppm. Forty‐five‐day‐old anthesic Cannabis plants were harvested and combined leaf and flower tissues were analyzed for cannabidiol (CBD) and Δ9‐tetrahydrocanna‐binol (Δ9THC). Nine essential elements were also measured in plant tissue. Plant growth, tissue yield, and concentration of CBD and Δ9THC were positively correlated with extractable P2O5 (p < 0.01). Phosphorus concentrations in tissue were similarly related to yield of dry matter and cannabinoid concentrations. Uptake of K was positively correlated with extractable K2O across all treatment levels (r=0.40**), but was negatively correlated with tissue yield (r=‐‐0.36**). Growth and tissue yields were negatively related to total plant N (p< 0.01). Levels of extractable P2O5, Mn, B, and Mg were associated with specific concentration ranges for several plant elements plus Δ9THC. Thus, it was possible to partially characterize a soil by tissue analysis. For example, all of the plants grown on soil with less than 100 ppm of extractable P2O5 contained less than 8,000 ppm Δ9THC. Usefulness of such relationships will be dependent upon extensive evaluation of Cannabis on different soils under various cultural conditions. At this time, the reliability required for determination of origin of Canabis derivatives via chemical analysis does not exist when only essential elements and cannabinoids are considered.

Mineralization and Gaseous Loss of Nitrogen in Soil‐Applied Liquid Sewage Sludge

AbstractBecause of the current interest in land disposal of sewage sludge, experiments were conducted to determine the rate of N mineralization in sludges. Sludge applications can then be adjusted to supply adequate N for maximum crop production but prevent excessive applications which would lead to NO3‐N pollution of ground water.A 2.5‐inch depth of liquid sewage sludge was either surface applied or incorporated with a quantity of soil and incubated under laboratory conditions. At the end of 18 weeks, NO3‐N accumulation was 22% of the applied N when the sludge was applied to the soil surface and 38% when the sludge was incorporated with the soil. Gaseous N losses ranged from 16 to 22% of the applied N in the incorporated treatment and 21 to 36% in the surface‐applied treatment. Only a small part of the gaseous N loss resulted from NH3 volatilization.

Lime Requirements of Natal Oxisols Based on Exchangeable Aluminum

AbstractThe exchangeable Al status of eight Natal Oxisols was found to be a suitable criterion for the measurement of lime requirement defined as the amount of lime necessary for maximum crop production. The principal function of lime in these soils was to eliminate Al toxicity; it had little or no effect on P availability. A “critical value” for exchangeable Al below which trudan (Sorghum sudanense) did not respond to lime application was found. On the average the amount of lime necessary for maximum growth and exchangeable Al control was approximately one‐sixth the amount required to raise the soil pH to 6.5.

Chemical hazards in agriculture.

To ensure maximum crop production, modern farmers must use a wide range of chemicals, including fertilizers, fuels, equipment sanitizers and protectants, refrigerants, and a wide range of pesticides to control weeds, fungi, insects and other adverse organisms. The uses and occupational health experience of these chemicals in Britain is described. Amongst them, pesticides are shown to require greatest care in use, especially insecticides. The major groups of chemicals are discussed in some detail and information is given on the statutory and voluntary measures taken to help ensure a high standard of safe use in recent years.

Atmospheric- and soil-induced water stresses in plants and their effects on transpiration and photosynthesis

A consideration of the natures of the plant processes of photosynthesis and transpiration reveals that a different type of water stress may be operative in the regulation of each of their rates. In particular, it is postulated that the water property which substantially controls photosynthesis is the free energy of the water in the vicinity of the chloroplasts, whereas the driving force in transpiration is identified as the difference between the free energy of water at this point in the leaves and that in the free atmosphere. Theoretical considerations indicate that the free energy of the water in the vicinity of the chloroplasts is chiefly controlled by the status of the soil moisture, but that the difference between the free energy of water at this point and that in the free atmosphere is determined almost wholly by the condition of atmospheric moisture. Calculations of the degree of independence of these two mechanisms indicate that plant photosynthesis may come within about 10% of being completely decoupled from the direct effects of atmospheric moisture content and that transpiration may to a similar degree be independent of soil moisture content. The limits within which these conclusions are felt to be generally valid are specified, and plant responses to drying soil in atmospheres of varying evaporative demand are predicted. The theory is then evaluated in the light of experiments reported in the literature, and implications are finally drawn from the generalizations proposed up to this point for the optimum frequency of irrigations needed to promote maximum crop productivity.