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.     

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.     

Weed Seed Bank Dynamics

Summary

Weeds continue to have major impacts on crop production in spite of efforts to eliminate them. Most weed species rely on seed for regeneration and persistence. The species composition and density of weed seed in the soil vary greatly and are closely linked to the cropping history of the land. Altering tillage practices changes patterns of soil disturbance and weed seed depth in the soil, which plays a role in weed species shifts. Crop rotation and weed control practices also impact the weed seed bank in the soil. Information on the weed seed bank should be a useful tool for integrated weed management. Decision aid models are being developed that use information on the composition of the weed seed bank to estimate weed populations, crop yield loss, and to recommend weed control tactics. Understanding weed seed bank dynamics can also be used to guide management practices. Improving and applying our understanding of weed seed and seed bank dynamics is essential to developing improved weed management systems.     

Integrating Agroecological Processes into Cropping Systems Research

Summary

Agroecology is defined as the application of ecological concepts and principles to the design and management of sustainable agroecosystems. By viewing cropping systems as agroecosystems, an understanding of the value of the emergent qualities of systems can become a guiding element in research design. A framework for applying this approach in cropping systems research in proposed. A protocol for researching the conversion to sustainable agriculture involves three levels of investigation. The first focuses on improving the efficiency of conventional farming inputs and practices in ways that reduce both their amounts and the environmental impacts of their use. The second focuses on substituting conventional inputs and practices with alternatives that meet broader environmental standards, such as certified organic. Since the problems addressed at these two levels continue to present themselves, a third level is proposed whereby the agroecosystem is redesigned so as to operate on the basis of a new set of ecological processes. At this third level, the emergent qualities of the system itself help prevent problems. Such an approach promotes the conversion to sustainability.     

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.     

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.     

Cropping Systems and Soil Quality

SUMMARY

Cropping system refers to temporal and spatial arrangements of crops, and management of soil, water and vegetation in order to optimize the biomass/agronomic production per unit area, per unit time and per unit input. Soil quality refers to its intrinsic attributes that govern biomass productivity and environment moderating capacity. It is the ability of soil to perform specific functions of interest to humans. Three components of soil quality (e.g., physical, chemical and biological) are determined by inherent soil characteristics, some of which can be altered by management. Soil quality and soil resilience are inter-related but dissimilar attributes. Resilient soils, which have the ability to restore their quality following a perturbation, have high soil quality and vice versa. Decline in soil quality sets-in-motion degradative processes, which are also of three types, namely physical (e.g., compaction, erosion), chemical (e.g., acidification, salinization) and biological (e.g., depletion of soil organic matter content). Soil degradation, a biophysical process but driven by socioeconomic and political causes, adversely affects biomass productivity and environment quality. Determinants of soil quality are influenced by cropping systems and related components. Dramatic increases in crop yields during the 20th century are attributed to genetic improvements in crops, fertilizer use, and improved cropping systems. Dependence on fertilizers and other input, however, need to be reduced by adopting cropping systems to enhance biological nitrogen fixation and use efficiency of water and nutrients through conservation tillage, cover crops, and improved methods of soil structure and nutrient management.     

Brazilian Agriculture: The Transition to Sustainability

SUMMARY

Brazil has a total area of 850 million ha, of which 90% is within the tropics. Historically, the system of exploitation of the land for agriculture and forestry was based on land clearing, cultivation for some years and then moving on to new areas. This process often left degraded areas behind, especially in the mountainous areas of the country. With modern agricultural technology, crops can be successfully grown in virtually any region of the country. The current challenge for Brazil is to feed its population and provide agricultural surpluses for the growing export markets, while preserving its rich and biologically-diverse native vegetation which still covers almost half of the country. The objective of this review is to trace the history of agricultural activity in this country, and to assess the sustainability of the cropping and pasture systems which today occupy the largest areas. At present approximately 50 million ha are under annual and perennial crops, while almost twice this area is under pastures. These pastures, predominately Brachiaria spp., are mostly in a degraded state due to lack of fertilization and over grazing. The various options available to recover these pastures or convert these areas for sustainable cropping are explained. In recent years, increasing proportions of soybean, wheat, and corn are produced under zero tillage which favors the conservation of soil organic matter. This not only radically reduces the risk of erosion but also increases the capacity of the soils to retain nutrients and water. Small holders who represent a considerable fraction of Brazil's food crop production, generally do not have access to fertilizers or other agricultural chemicals. They obtain very low yields and their farming practices exhaust the soil of nutrients. The Brazilian sugarcane industry is the largest in the world and recent changes in the management of this crop and its impact upon sustainability issues are also discussed. Brazil also has vast areas of degraded pastures and abandoned hillsides that can be used for agricultural expansion. This would prevent further destruction of native vegetation and its accompanying biological diversity for agriculture.     

Numerical Modeling to Study the Fate of Nitrogen in Cropping Systems and Best Management Case Studies

Summary

Nitrogen (N) availability for crop uptake is dependent on various factors that influence the transformation of N sources and transport of N forms in soils. The fate and transport of N is site specific. Therefore evaluation of N dynamics under each condition is neither practical nor feasible. Simulation models which are adequately calibrated and tested can be used to estimate the fate and transport of N as well as crop responses under different production systems. These evaluations provide some guidelines as how to manage N and water efficiently to maximize the N uptake efficiency and minimize the losses. Thus, they contribute to the development of N and water best management practices. In this chapter, we discuss recent information on experimentally measuring the water and nutrient transport in soils as well as performing estimations using simulation models. The development and application of different simulation models for different production systems have been summarized. Some case studies on nitrogen and water best management practices are also discussed.     

Salt,Water, and Groundwater Management Models to Determine Sustainable Cropping Patterns in Shallow Saline Groundwater Regions of Australia

SUMMARY

This article describes models which can consider the interactions between plants, soils, water, irrigation practices, crop yields, and economics under shallow, saline groundwater conditions. Personal computing capability has now made it possible to develop a range of interactive modeling tools based on existing and new biophysical concepts. In view of the large number of available models, it is not possible to cover all modeling efforts in a single article. Hence, the discussion in this article is limited to farm and irrigation area scale salt, water, and groundwater management models. It provides an introduction to the SWAGMAN suite of models that have been used in Australia to determine sustainable cropping patterns under shallow, saline water table conditions. Salient features and applications of a detailed process based model (SWAGMAN Destiny), a lumped hydrologic economic model (SWAGMAN Farm) and a distributed biophysical model (SWAGSIM) are provided.     

Cropping Systems in Eastern Europe: Past,Present, and Future

SUMMARY

The evolution of cropping systems in Eastern Europe has been a long and gradual process. The objective of this paper is to provide a comprehensive review of the cropping systems in Eastern Europe before World War II, the present cropping systems, and speculate on the future systems. Before World War II, the crop-long term fallow, the grass-crop, and the field rotation were the prominent cropping systems. Crop rotations were adopted in the 16th–17th century and various modifications of the ‘Norfolk’ and the ‘crop-grass’ rotation systems were used. Cash cropping, industrial cropping, and monoculture were extensively used after World War II. Major political, social, and economic changes took place in Eastern Europe after the dissolution of the Soviet Union. Nationalized land was returned to rightful owners. The new owners, however, lacked the skills and financial resources for intensive crop production and this has resulted in drastic reductions in crop yields. Integrated crop production seems to be the most viable option for the East European countries because organic or biological cropping is financially too demanding. Considerable efforts are being made to design new cropping systems which emphasize reductions in mineral fertilizers and pesticides, and conservation tillage. Eastern Europe may become important exporters of agricultural commodities by the year 2020.     

Brassicacea-based management strategies as an alternative to combat nematode pests: A synopsis

Nematode pests parasitise and cause substantial crop yield and quality losses to a wide range of crops worldwide. To minimize such damage, the exploitation and development of alternative nematode control strategies are becoming increasingly important, particularly as a result of global efforts to conserve the ozone layer as well as our soil and water substrates. Inclusion of Brassicaceae crops in cropping systems is one such alternative and has been demonstrated in most cases to be effective in managing the top-three rated economically important nematode pests, viz. root-knot (Meloidogyne), cyst (Heterodera and Globodera) and lesion (Pratylenchus) nematodes as well as others. In the past nematode pests were and still are generally managed successfully by the use of synthetically-derived nematicides, which are progressively being removed from world markets. However, fragmented and limited information about the use of Brassicaceae crops as a nematode management tool exists in various countries. The need thus arose to summarize, compare and discuss the vast amount of information that has been generated on this topic in a concise article. This paper therefore represents a comprehensive, practical and critical review of the use and effect(s) of Brassicaceae-based management strategies and the biofumigation and cover-crop/rotation characteristics of Brassicaceae in reducing nematode-pest population levels in global cropping systems.     

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.     

Research Priorities in Natural Systems Agriculture

SUMMARY

Over the course of millennia and most dramatically in recent years, agriculture has eroded natural capital as it has supplied human demands. These tendencies can be offset by infusions of fossil fuels for fertility, pest control and traction, but only partially and not over the long term. This could be called the “problem of agriculture,” in contrast to problems in agriculture. Natural ecosystems are unmatched for efficient nutrient recycling, solar energy use, and biodiversity preservation, but they cannot feed dense human populations. An ecological agriculture that is a synthesis of natural and agricultural systems can save soils from erosion and reduce chemical and water use. Reducing chemical pollution of air, water and soils will conserve wildlife habitat, improve water quantity and quality and protect human health. By practicing an agriculture that has conservation as a direct result, farmers can become better stewards of the land. Lower input costs and inherent sustained soil fertility will mean more profit for farmers and communities. Principles of natural systems agriculture (NSA) are applicable to any food- or fiber-production system worldwide. In the central Great Plains of the United States, agriculture should mimic the native prairie, which is a polyculture of herbaceous perennial plants. The Land Institute has spent 25 years studying the structure and function of prairies. Now we and other research organizations are breeding perennial grain crops, including cool- and warm-season grasses, legumes, and composites. We are following two parallel strategies: selecting wild perennials for greater seed production and other traits of domestication and hybridizing wild perennials with annual crops to combine desired traits. Although the breeding process will take many years, the effort will be repaid many times over if we achieve our goal: a lasting solution to the 10,000-year-old problem of agriculture.     

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.     

Factors determining the adoption of laser land leveling in the irrigated rice–wheat system in Haryana,India

Laser land leveling has been increasingly adopted in the irrigated rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping system in the state of Haryana (India), located in the north-western Indo-Gangetic Plains. Still, many farmers have applied it to only a fraction of their land. In this study, we used data collected from 621 farm households in Haryana and applied a double-hurdle model for assessing the factors that determine the adoption and intensity of laser-leveling technology. The results show that large land holders are more likely to laser level their farm land; however, we found a negative association between land holdings and the proportion of laser-leveled land. Information about technology through farmer-to-farmer communication and through private traders, participation in agricultural training and membership in local agricultural institutions increased both the likelihood and the intensity of adoption. Our findings call for a closer collaboration among the various stakeholders, specifically to promote farmer-to-farmer communication through increased participation in local institutions and increase the rate of adoption of laser leveling technology.     

Annual Nutrient Balance and Soil Chemical Properties in Heavy Multiple Cropping System in the Coastal Area of Southeast Lake Dianchi,Yunnan Province,China

Abstract

To ensure higher yields, farmers in China have increased cropping intensity with a large input of chemical fertilizer and livestock manure since 1980s, which has led to unsustainable agricultural productivity and environmental quality. This study aimed to evaluate the effects of intensive cropping on nutrient absorption and biomass production of crops and to determine the controllable source of residual nutrients in soil in the coastal area of Lake Dianchi, China. Soil and crops were sampled in 32 vegetable fields and four paddy fields; and simultaneously surveyed. In vegetable fields, cropping intensity and input to each crop were extremely high; and, 58, 72, and 20% of nitrogen, phosphorus, and potassium were not absorbed by the crop. Nitrogen absorption ratios of the vegetables were low. The amount of nitrogen absorbed from sources other than chemical fertilizer by vegetables, namely, from soil, manure, or irrigation water, in the fields with three to nine years cultivation duration was higher than those with zero to two years cultivation duration. Reduction of input should be more efficient than enhancing output to decrease soil nitrogen, phosphorus, and potassium; and, reducing input of chemical fertilizer should be more efficient than reducing input of manure. These results should be helpful for reducing agricultural pollution in China.     

The effects of spatial variability of land use on stream water quality in a costal watershed

Researchers generally accept that land use types within a watershed closely relate with the water quality characteristics of streams. Despite numerous studies investigating the relationships between water quality and land use, there are increasing concerns about the geographical variation and lack of spatial integration in previous studies. We investigated the relationships between land use and water quality characteristics including biological oxygen demand (BOD₅), total nitrogen (TN), total phosphorus (TP), and Escherichia coli in the Wha-Ong estuarine reservoir watershed in Korea, which has spatially integrated land uses. Residential and paddy areas appear to be positively and negatively correlated, respectively, with degraded water quality. The spatial variations of these relationships were also examined using zonal analysis. Some results contrasted with those of previous studies that were conducted mostly in developed Western countries and may reflect the different land use intensities and agricultural practices in Korea. Relationships across zones, distinguished by distances from streams, were inconsistent and erratic, suggesting that the relationships between remote land uses and water quality may be affected more significantly by sub-basin characteristics than by the land use itself. The geographical differences and spatial variations found in this study indicate that caution must be taken in generalizing the relationship between land use and water quality.     

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.     

Evaluating Soil Organic Matter Changes Induced by Reclamation

Summary

Evaluating soil conservation and plant production on reclaimed lands requires an understanding of the rate of change in soil organic matter (SOM) under specific land use systems and management practices. By using a geographic information system (GIS), changes in the SOM status were assessed and mapped at an experimental station in subtropical China after eleven years of reclamation. Maps of soil survey, land use and topographic information of the experimental station were entered into the computer after digitalization, and a land unit map was produced by overlaying these maps. The SOM levels in different time periods were entered and combined with their corresponding land units in the land unit map, and their differences (?SOM) in time for each land unit were calculated. SOM changes at the experimental station were then assessed and mapped based on the ?SOM values. The changing status in various land use systems, soil types and relief patterns could be shown in the computer. SOM changes varied with land use systems and the original SOM levels. After 11 years of reclamation, the soils with SOM levels of > 30 and < 10 g Kg^?1 decreased 95.3% and 30.9% in area, respectively, while those with SOM levels of 20-30 and 10-20 g Kg^?1 increased 44.3% and 8.4%, respectively. The SOM content in paddy fields, vegetable fields, pastures, and grasslands increased due to reclamation practices, but decreased in fuel woods, sparse weed land, and bare land.