Cropping Systems and Integrated Pest Management: Examples from Selected Crops

SUMMARY

Cropping systems have been central to managing associated pests for centuries. This treatment focuses on the history, concepts, and the integration of available Integrated Pest Management (IPM) tools/strategies into cropping systems. Pest assessments/diagnoses, IPM-decision-making aids, and examples of pest management in selected crops/cropping systems (wheat, soybean, corn, cotton, potato, and strawberry) as well as emerging opportunities and challenges are discussed. The evolving philosophy of IPM and the recently renewed emphasis on ecologically based pest management address the fact that significant levels of predation and/or parasitism are desirable insofar as they promote diversity and sustainability of agroecosystems. Thus, cropping systems are beginning to focus on soil and crop health as well as specific IPM and production goals. Although extensive efforts have been directed toward modeling the many interactions between crops, associated pests and the environment, the general implementation of a systems approach to integrated crop and pest management remains to be accomplished.     

An Agroecological Basis for Designing Diversified Cropping Systems in the Tropics

Summary

Small scale diversified systems which rely mostly on local resources and complex crop arrangements, are reasonably productive and stable, exhibiting a high return per unit of labor and energy. In many ways complex polycultures and agroforestry systems used by small tropical farmers mimic the structure and function of natural communities therefore acquiring many features typical of such communities, such as tight nutrient cycling, resistance to pest invasion, vertical structure, and high levels of biodiversity.

An agroecological approach to improve tropical small farming systems must ensure that promoted systems and technologies are suited to the specific environmental and socio-economic conditions of small farmers, without increasing risk or dependence on external inputs. Rather, agroecological development projects should incorporate elements of traditional agricultural knowledge and modern agricultural science, featuring resource-conserving yet highly productive systems such as polycultures, agroforestry, and the integration of crops and livestock.

It is ecologically futile to promote mechanized monocultures in areas of overwhelming biotic intricacy where pests flourish year-round and nutrient leaching is a major constraint. Here, it pays to imitate natural cycles rather than struggle to impose simplistic ecosystems that are not inherently complex. For this reason, many researchers think that successional ecosystems can be particularly appropriate templates for the design of sustainable tropical agroecosystems.     

Weed Biology,Cropping Systems,and Weed Management

SUMMARY

Weeds pose a recurrent threat to agricultural productivity in both industrialized and developing countries. Weeds respond dynamically to all cropping practices, and therefore, the design and function of cropping systems plays a central role in the composition of weed communities. The unique and challenging nature of weed communities requires more integrated approaches to weed management than are currently being employed by most growers. Integrating weed management with cropping system design and application may be an effective approach to diversifying weed management systems. Each crop-weed system is a unique mix of genetics and biology and will respond dynamically to changes in management practices. Practices such as crop rotation, tillage, cover crops, and fertility management modify weed populations. The challenge is to integrate these and other practices with the best available control tactics to generate integrated management systems. Cropping system design provides an excellent framework for developing and applying integrated approaches to weed management because it allows for new and creative ways of meeting the challenge of managing weeds. Weed science must integrate the theories and application of weed management into cropping system design based on the unique characteristics of weed communities and the available weed management options.     

Improving Soil Quality

Abstract

Future advancements in crop production will rely on increased understanding of ecological principles that control interactions among cropping system components. Our interest in linking soil quality and weed management derives from the belief that greater understanding of key processes and properties that define soil-weed relationships will lead to the design of agroecosystems with greater capacity and opportunity to suppress weeds. We identified seed-bank persistence, seedling establishment, and interspecific interference as key processes that affect annual weed population dynamics. We then examined how soil processes and properties can affect each of these factors and how, in turn, soil-improving management practices and cropping system design may affect weed dynamics. We established weed-related soil management objectives as: (i) reducing the persistence of seeds in the soil; (ii) reducing the abundance of safe-sites for weed establishment and the filling of available sites; and (iii) reducing crop yield loss caused by a given density of weeds. Soil factors that can be managed to achieve these goals include: (i) chemical, physical, and biological conditions that affect resources required for weed seed germination, establishment and growth; (ii) habitat for herbivores and pathogens that attack weed seeds and seedlings; and (iii) phytotoxin production. We concluded that many as yet unexplored opportunities exist to manipulate the soil environment and to design cropping systems that create multiple weed suppressive conditions at critical junctures of weed seed-bank persistence, establishment, and interference.     

Conceptual Model for Sustainable Cropping Systems in the Southeast: Cotton System

SUMMARY

Many small to mid-size family farms face an economic and ecological crisis due to the changing face of agricultural production. Increasing production costs and lower revenues are causing many producers to leave the farm. Rural communities face economic hardships due to declining farm numbers and continued loss of the brightest youths who often seek employment in urban areas. Small to mid-size family farms and rural communities can be sustainable if economic and environmental risks are recognized and solutions developed that reach all members of the farm and rural communities. Our project focuses on the involvement of farmers, scientists, and other stakeholders to enhance understanding of sustainable principles at the farm level and extend awareness of the central components to sustainability of rural communities. Conservation tillage with cover crops is being used to modify pest pressures, reduce chemical inputs, improve soil productivity and reduce environmental risks to producers, the community and the environment in cotton (Gossypium hirsutum L.) production systems. Preliminary results indicate that reductions in use of pesticides can be achieved due to enhanced presence of beneficial insects. Cotton offers the best opportunity to enhance the understanding and use of sustainable practices in ecologically-based farming systems because of its predominance in southern farm enterprises. Farmer participation and understanding is being facilitated through the participation of the farmer based Georgia Conservation Tillage Alliance. To achieve greater outreach and broaden community participation within the region we are involving at-risk rural youth through the Communities in Schools of Georgia program. Outreach includes the use of traditional and newer internet based technologies through the development of databases and expert systems that allow, farmers, ranchers, and community members an opportunity to evaluate economic and environmental effects of alternative production practices at local and regional scales. Through interactions with existing federal, state, and private organizations we are encouraging expansion of these sustainable approaches regionally.     

Soil Ecosystem Changes During the Transition to No-Till Cropping

Summary

Growers in the United States and worldwide are adopting no-tillage (no-till) cropping to reduce soil erosion, improve soil quality, increase water infiltration, and reduce number of passes with farm equipment over their fields. Soil erosion from dry farmed (i.e., non-irrigated) cropland in most regions of the United States exceeds the tolerable rate. An understanding of the changes in the soil ecosystem with changing tillage practices is needed to minimize the impact of agriculture on the environment and foster the use of sustainable agricultural practices. The soil biota is critical to the functioning of any agro-ecosystem, but studying the soil biota is difficult due to the diversity and the challenges associated with isolating and identifying these organisms. Soil disturbance or lack of disturbance can have a profound effect on biotic populations, processes and community structure. This contribution examines changes that occur in soil during the transition to no-till cropping, interrelations among organisms in the soil food web, and the relationships between organisms and their environment. As interest grows in sustainable cropping systems that mimic processes and soil organic matter turnover of native, undisturbed systems, it is imperative to understand how the transition to no-till affects an organism's niche, or functional role within the soil environment. Ecosystem investigations will enhance the understanding of changes that occur with the adoption of reduced tillage and no-till cropping systems so that these systems become increasingly viable.     

Soil Weed Seed Banks and Weed Management

Abstract

Studies of soil weed seed banks are of relatively recent origin considering their importance as sources of diversity and continued occupation of many types of habitats, including agroecosystems. The management of weed seed banks is based on knowledge and modification of the behavior of seeds within the soil seed bank matrix. The behavior of seeds defines the phenotypic composition of the floral community of a field. Selection and adaptation over time have led to the highly successful weed populations that exploit resources unused by crops. The weed species infesting agricultural seed banks are those populations that have found successful trait compromises within and between the five roles of seeds: dispersal and colonization, persistence, embryonic food supply, display of genetic diversity, and as a means of species multiplication. Diverse weed seed populations provide seed banks the opportunity to exploit any change in conditions to ensure their enduring survival and spread. The soil seed bank matrix is the spatial arrangement of environmental and physical factors over time. The behavior of soil seed banks at any level of biological, spatial, or temporal organization is a consequence of the accumulated, emergent behavior at lower levels of organization. Weed seed behavior arises from their sensitivity to environmental conditions within the physical structure of the soil seed bank. This sensitivity is reflected in changes of short duration (e.g., germination), during the annual life cycle, over multiple years (e.g., population shifts), and over evolutionary time. Understanding the processes that drive and control seed behavior will allow us to manipulate and manage weed seed banks in an economic and sustainable manner. This knowledge will allow us to implement improved, more informed, weed management systems and strategies. Important weed bank management strategies include prevention of seed introduction on farm, acquisition of weed biology information (including predictive tools), decision making about weed seed infestation levels and their implementation (eradication, reduction, tolerance), weed seed population shifts (within the seed bank, between species, increased diversity), and manipulations encouraging beneficial weed species. Environmental modification and changes in cropping systems can also be of considerable strategic importance in weed management.     

A Framework for Economic Analysis of Cropping Systems: Profitability,Risk Management,and Resource Allocation

SUMMARY

A cropping system must be economically viable for it to be sustainable. This study focuses upon the economic components of profitability, risk management potential, and optimal resource allocation. Some of the primary aspects of economic analysis of cropping systems to a broad multidisciplinary audience of researchers, extension specialists, graduate students, and senior undergraduate students are addressed. Analytical economic tools are discussed including data requirements, advantages, and disadvantages of each method. A case study of a Henderson, Kentucky producer is presented as a primary example along with empirical applications from the literature. The importance of various types of economic analysis is demonstrated through the selection of different production decisions dependent on the level of economic analysis included.     

Weed Thresholds

Abstract

Weed thresholds are an integral component of an integrated weed management system (IWM). In this paper we review the literature on weed thresholds and examine the theory and applicability of thresholds within the context of a systems approach to IWM. The development of empirical models describing single and multi-species thresholds are reviewed and discussed in terms of the magnitude of weed threshold values in various crops and the importance and limitations of the parameters used to calculate these values. Mechanistic weed threshold crop competition models are suggested as a means of overcoming some of the limitations of empirically based threshold models. A mechanistic approach to the development of weed threshold models is desirable since relative crop and weed responses to environmental factors, cultural practices and the dynamic nature of competition are considered. Guidelines for the application of weed thresholds within a cropping system are outlined.     

Forage Legumes for Sustainable Cropping Systems

SUMMARY

Perennial and annual forage legumes are important components of sustainable cropping systems. Forage legumes are a primary source of forage to supply protein and fiber for livestock rations. They can be grazed, or stored as hay or silage. They contribute biologically fixed N and sustain the soil by reducing erosion and increasing soil organic matter levels. Diversifying cropping systems by including legumes can also reduce weed, insect, and disease incidence. Potential new uses of legumes include phytoremediation of N contaminated sites and capturing N lost from cropping systems. Legumes also have potential use as a feedstock for renewable energy production. Legumes have traditionally been used in rotation with grain crops but more recently have been shown promise as winter cover crops, intercrops with grain crops, and as living mulches. In this review, we discuss traditional and new roles of forage legumes in sustainable cropping systems with examples primarily chosen from northern USA and Canada.     

Problems and Perspectives of Yam-Based Cropping Systems in Africa

SUMMARY

Yams (Dioscorea spp.) constitute an important starchy staple in sub-Saharan Africa (SSA) where food security for a growing population is a critical issue. Mixed cropping in yam based systems is the norm in the region and productivity of yams in these systems is below potential. It is concluded that there is much scope for improvement of yam based cropping systems in SSA in order to meet the needs of the region. The strategy of crop breeding to select yam varieties suitable for various cropping systems must consider a truly multidisciplinary systems approach. Further manipulation must be made to tuber dormancy to expand flexibility in field propagation in different cropping systems and improve storage and marketing. The sustainability of yam based cropping systems in SSA could improve if agronomic research was focused on strategies for improving soil fertility, weed and pest management including design of cropping systems and suitable rotations.     

Sustainability of the Rice-Wheat Cropping System

Abstract

The rice-wheat cropping system of the Indo-Gangetic Plains (IGP) has contributed tremendously to food security of the region. However, of late there has been a significant slowdown in yield growth rate of this system and the sustainability of this important cropping system is at stake. A decline in soil productivity, particularly of organic C and N, a deterioration in soil physical characteristics, a delay in sowing of wheat, and decreasing water availability are often suggested as the causes of this slowdown in productivity. Therefore, a paradigm shift is required for enhancing the system's productivity and sustainability. Resource-conserving technologies involving zero-or minimum tillage with direct seeding, improved water-use efficiency, innovations in residue management to avoid straw burning, and crop diversification should assist in achieving sustainable productivity and allow farmers to minimize inputs, maximize yields, conserve the natural resource base, reduce risk due to both environmental and economic factors, and increase profitability.     

Research and Extension Supporting Ecologically Based IPM Systems

Summary

Integrated Pest Management (IPM) has a long history of developing pest management strategies based on ecological principles. While IPM systems differ in their reliance on chemical controls, an ecological approach to IPM offers opportunities both to test ecological theory and to develop novel pest management techniques. We review ecological concepts relevant to habitat management as a tool for managing pest and natural enemy populations in annual cropping systems, and we describe a case study of the impacts of habitat management on predatory ground beetles (Coleoptera: Carabidae) in annual cropping systems. Experimental manipulation of carabid population density revealed a positive relationship between the abundance of carabids in cropland and prey removal. Provision of stable refuge habitats in annual crops increased carabid species richness and abundance. Further studies demonstrated that the presence of refuge habitats mitigated the impacts of insecticide disturbance on carabid abundance and community structure in adjacent cropland. These results were used as part of a program to educate extension agents and producers in the principles of agroecology and ecologically based pest management. We encourage extension agents and producers to test novel practices using adaptive management. In this approach, predictions are formulated regarding specific management practices and evaluated against the results. Based on these observations, management is then adapted to yield the desired outcome. Such an approach recognizes the inherent uncertainty of multifactor ecological manipulation while providing producers with methods to manage this uncertainty.     

Vegetation management and biological control in agroecosystems

The application of diversity/stability considerations in theoretical ecology has led to the emergence of testable hypotheses with implications for biological control and agroecosystem management. The object of applied research in this area has been to achiece predictably stable pest populations (below an economic threshold level) in crop systems. The exacerbation of most insect-pest problems has been associated with increases in crop monocultures at the expense of the natural vegetation, thereby decreasing local habitat diversity. This can seriously affect the abundance and efficiency of natural enemies, which depend on habitat complexity for sources of alternate prey/hosts, pollen and nectar, shelter, nesting and overwintering sites. Plant diversification of agroecosystems can result in increased environmental opportunities for natural enemies and, consequently, improved biological pest control. Agronomically, there are several ways to design plsnt-diverse cropping systems. One way is by manipulating the vegetation of field margins, and managing the species composition and density of plants in ditchbanks, hedgerows, windbreaks and other types of shelter belts. Within-field plant diversity can be manipulated by designing polycultures of various temporal and spatial crop arrangements. The effects of some of these systems on the dynamics of insect populations are discussed, as well as the effects of cover-crop management on pest insects in orchards. Another way to enrich the vegetational structure of cropping systems is through weed management. Weed diversity in the form of weed borders, alternate rows, or by providing weeds in certain periods of the crop growth can have a major impact on insect dynamics.     

The Importance of Biodiversity in Agroecosystems

SUMMARY

This article identifies the important functions and benefits of biodiversity in agriculture, for sustainable crop production and food security. After clarifying impacts from the decline of biodiversity in agriculture, the article summarizes principles, practices and policies for biodiversity conservation and enhancement in farming systems and in landscapes. Some of the strategies identified build upon valuable local experiences and knowledge in traditional farming practices, while others take advantage of recent scientific findings in agroecology and ecosystem health. The analysis suggests the value of adopting an agroeco-systems approach, beyond a focus on genetic resource conservation alone-to implement other biodiversity-enhancing methods in farms, such as integrated ecological pest and soil management. Attention is also given to the challenges by conflicting agricultural policies that contribute to the decline of biodiversity in farming systems, and potential of reforming such policies. The practices and approaches reviewed in this analysis show effective ways to link biodiversity conservation and sustainable agriculture.     

The Role of Nitrogen Fixation in Crop Production

Summary

Biological nitrogen fixation is an important process for agricultural productivity in many cropping systems because of direct inputs of atmospheric nitrogen, and rotational effects such as disease control. Advances in molecular biology techniques provide new opportunities to understand the ecology of root nodule bacteria and may improve the selection of elite strains for inoculation. An understanding of the genetic basis of nodulation in grain and pasture legumes may improve inoculation technologies. Temperate and tropical pastures may be improved through effective inoculation, removal of nutritional constraints, and use of alternate legume species. Increases in nitrogen fixation in crop legumes may result from addressing problems in the legume host, the microsymbiont and the environment.     

Effect of Supplementing Inorganic Fertilizer with OrganicFertilizer on Growth and Yield of Rice-Cowpea Mixed Crop

Abstract

With the renewed interest in mixed cropping and the increasing awareness of environmental degradation arising from high chemical inputs, this experiment was conducted to assess the effect of supplementing inorganic with an organic fertilizer on the growth and yield of rice and cowpea under the mixed cropping system. Treatments comprised six sole crops and three mixed crops, each under 100% NPK (C), 50%NPK+ 50% cow dung (CCD) and cow dung alone (CD). The fertilizer treatments did not significantly affect cowpea performance. However, the number of panicles per hill and the number of spikelets per panicle of rice were higher under mixed cropping than under sole cropping. On the average, rice grain yield was significantly lower under the mixed cropping than under the sole cropping. The land equivalent ratios increased under all the fertilizer treatments indicating the efficiency of the mixed-cropping system. The results of the experiment suggest that rice– cowpea mixed cropping under CCD and CD is a viable production option.     

Effects of Key Soil Organisms on Nutrient Dynamics in Temperate Agroecosystems

Summary

Soil organisms are a diverse group that can influence the nutrient dynamics in temperate agroecosystems profoundly. Many organisms interact in a symbiotic or mutualistic way with plants, and these relationships have co-evolved, permitting plants and soil organisms to flourish in the soil environment. Numerous controlled lab or small plot-scale studies have demonstrated that soil organisms can mobilize or transfer substantial quantities of nutrients to crops, in relationship to crop requirements. However, the simple scaling up of such results to explain conditions on a large field scale is very much constrained by a lack of information on the spatio-temporal distribution of soil organisms in temperate agroecosystems. The numbers, diversity and activity of soil organisms in temperate agroecosystems are affected by agricultural management practices such as tillage operations, but our knowledge of the key organisms or groups of organisms that contribute to nutrient cycling and crop production under different sets of management practices is limited. Better management of nutrients in temperate agroecosystems requires better knowledge of soil biota, their effects on nutrient cycling and their contribution to crop production.     

Expanding the Context of Weed Management

Abstract

Concerns about current weed control practices have increased the consideration of new weed management strategies. In recent times, weed control practices for major crops have been influenced greatly by the availability of selective herbicides. Herbicides are critical tools, but weed science must integrate more components to create weed management systems. Changes in weed management can be attained within the framework of existing cropping systems. However, for the longer term, new methods and approaches to weed management are needed. Weed scientists need to play a central role in the development of new cropping systems to make weed management an integral component of the system. This volume contains a series of review articles and original research that presents innovative approaches to weeds and weed management. It is our hope that these papers will stimulate discussion on a broader view of weeds and weed management.     

DIVECOSYS: Bringing together researchers to design ecologically-based pest management for small-scale farming systems in West Africa

Crop pests are a major constraint to the intensification of agricultural production in the tropics, with novel issues related to global change (climate, land use, biological invasions, etc.), food security and preservation of natural resources and biodiversity. A research, extension and education network called DIVECOSYS (Diversity of cropping systems and ecologically-based pest management in West Africa) was launched in 2010 to synergize applied research actions in response to growing concerns on the vulnerability of agricultural systems to pest management in West Africa. This scientific network brings together research and academic institutions, with expertise spanning a multidisciplinary perspective from biology and ecology to remote sensing, agronomy and integrated pest management. Its main scientific objective is to explore the potential of biodiversity and ecological processes such as pest regulation, enabling novel ecologically-based models for productive systems, reduction of pesticide use, and adaptation or resilience of farming systems in the face of environmental disruptions. From Northern Senegal to Southern Benin, the research group explores a wide range of ecoregions and socio-ecological contexts, including stakeholders and their objectives, land use and agricultural practices, and management of biodiversity for enhancing biological control. Main challenges to be turned into opportunities include (i) encouraging collaborations amongst researchers from different scientific fields, (ii) fostering interactive research and synergies among research institutions and among countries, and (iii) developing an ecological engineering approach for the design of sustainable agricultural systems for smallholder farmers.