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.     

Managing Soil Fertility Decline

Summary

Soil fertility is defined in terms of the ability of the soil to maximize plant productivity, often within economic constraints. A decline in natural soil fertility seems to have occurred over all civilizations. Overgrazing and deforestation are the two most important factors affecting global soil degradation. Nutrient losses from agricultural systems are broadly divided into losses through volatilization, losses from leaching, losses due to product removal, losses to non-labile soil pools and losses from various forms of erosion. Rapid declines in soil fertility are associated with large demands for food due to expanding population, nutrient mining of agricultural areas with concomitant shifts of produce to cities, and intensification of agricultural activities without proper regard for long-term maintenance of fertility by application of fertilizers, recycling of organic wastes, liming to combat acidification, fallowing, rotations and prevention of large scale soil erosion. Agricultural policy has often encouraged soil fertility decline and soil degradation. In the future, agricultural scientists must have major inputs into the development and implementation of policy.     

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.     

Relationship between F4 Individuals and F5 Lines in Cooking Quality of Rice

Abstract

The response of microarthropod populations to different combinations of conservations! agricultural practices was investigated in two field experiments. In the first experiment, cropping systems with combinations of tillage (conventional or reduced), biocide application (conventional or reduced), and fertilization (chemical or cattle manure compost) were compared. In the second experiment, five treatments including four fallow managements that received different levels of tillage, biocide, and organic matter input from vegetation were compared. The springtail (Collembola) population was higher with less tillage, less biocide application, and more organic matter input in both experiments, and these effects were additive; there was no specific combination of practices that has an interacting effect. The mite (Acari) population was also higher under most conservations! treatments, and a significant interaction effect between tillage and organic matter application was found. A large increase in the Acari population under the combination of reduced tillage and higher organic matter input suggested that beneficial effects of these practices on the Acari community could be increased by integrating these practices. There was no significant correlation between the microarthropod populations and plant cover or soil chemical/physical properties measured. Slight changes in soil environments caused by agricultural practices may affect microarthropod communities substantially even before the changes in soil properties become detectable.     

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.     

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.     

SWAT modeling of best management practices for Chungju dam watershed in South Korea under future climate change scenarios

Suitable and practicable best management practices (BMPs) need to be developed due to steadily increasing agricultural land development, intensified fertilization practices, and increased soil erosion and pollutant loads from cultivated areas. The soil and water assessment tool model was used to evaluate the present and future proper BMP scenarios for Chungju dam watershed (6,642 km²) of South Korea, which includes rice paddy and upland crop areas. The present (1981–2010) and future (2040s and 2080s) BMPs of streambank stabilization, building recharge structures, conservation tillage, and terrace and contour farming were examined individually in terms of reducing nonpoint source pollution loads by applying MIROC3.2 HiRes A1B and B1 scenarios. Streambank stabilization achieved the highest reductions in sediment and T-N, and slope terracing was a highly effective BMP for sediment and T-P removal in both present and future climate conditions.     

Classical Farming Systems of China

Summary

During the long and dramatic history of agricultural civilization, a variety of technological methods have been developed and many valuable experiences accumulated on the farming practices. This review describes the progression of the agricultural development in ancient China. The practices and philosophies of classical farming in different historical periods are expounded and the characteristics of the classic farming practices in China are summarized. The paper also describes regeneration of the organic farming system, the development of the ecological and sustainable agricultural systems, the realistic significance of the knowledge of the classic farming methods such as application of organic manure and the systems of crop rotation and intercropping.     

Limited Increase of Agricultural Soil Carbon and Nitrogen Stocks Due to Increased Atmospheric CO2 Concentrations

SUMMARY

Increased atmospheric concentrations of CO₂ may lead to increases in agricultural soil carbon and nitrogen storage, but the impact is likely to be small and is uncertain due to limitations in other resources (e.g., nutrients, water) and interactions with climatic changes. Since only a small percentage of carbon added to the soil becomes stabilised, the impact of CO₂ fertilisation of crops is considered to be very small compared to deliberate efforts to increase soil carbon by improved agricultural management. Even if agricultural soil carbon stocks are increased, carbon credits cannot be claimed under the Kyoto Protocol since the increases are not directly human-induced, a condition which must be met in order for any carbon sink to be included in emission reduction targets.     

Nutrient Dynamics

Summary

Environmental concerns currently trigger the development of more sustainable soil fertility management strategies. It appears that effective sustainable practices are those that enhance natural soil processes. Soil processes include the decomposition of residues and mineralization of organic matter, nitrogen fixation, nitrification, nitrate leaching, denitrification and sulfur reduction. Natural soil processes also include less well-understood interactions, namely, those leading to the dissolution of minerals by organic acids, as well as rhizospheric and mycorrhizospheric interactions. Plants, associated with arbuscular mycorrhizal symbionts, supply and distribute carbon and energy, sustaining most of the biotic mechanisms responsible for nutrient release from soil, and maintaining organic pools of nutrients. Among these pools, the microbial biomass and fine roots pools, with their very fast turnover time, are particularly important as they can maintain large amounts of nutrients in very labile form and, therefore, increase soil fertility. Agricultural soil systems are very dynamic and are characterized by large spatial and temporal variations, which are largely driven by plant development. In addition, nutrient dynamics in agricultural soil systems seem particularly influenced by temperature, moisture, and nitrogen and phosphorus fertilization. Nitrogen losses from soil are reduced in systems where nitrogen release corresponds to plant demand. Biological nitrogen fixation is a sound way to input nitrogen in cropping systems. Phosphorus losses can be reduced through increased reliance on the arbuscular mycorrhizal symbiosis of crops. Soils are diverse and complex systems, which, furthermore, respond to increasingly unpredictable climatic variations. Optimal agricultural soil management is a moving target and, hence, a challenging goal that will never be totally reached.     

Cassava-Based Intercropping Systems on Sumatra Island in Indonesia: Productivity,Soil Erosion,and Rooting Zone

Abstract

In Gunung Batin, the southern end of Sumatra Island, Indonesia, cassava is widely cultivated on gently sloping areas for starch materials. The monoculture system and/or the intercropping system without legume plants commonly adopted in this region may tend to accelerate soil degradation. The objective of this study is to compare the productivity among several cassava cropping patterns to propose the most beneficial one in this region. A field experiment of five cropping patterns {cassava (Manihot esculenta Crantz) single-cropping, three cassava-based intercropping patterns, and a crop rotation} was conducted for three years. The cropping pattern that recorded the highest net income varied with the year. In 1997, the driest year of the past several decades, cassava single-cropping was the highest in income. The proposed intercropping system {cassava/(maize ? soybean ? cowpea)} was the highest in 1998, a year with moderate rainfall. In 1999, when severe insect damage occurred to legume crops, the farmers?conventional intercropping was the highest. In an average of the three years, the proposed intercropping pattern was same as cassava single-cropping, although cowpea cultivation as the dry season cropping was not possible in this region. The amount of soil erosion was relatively high in cassava monoculture in comparison with the other intercropping and crop-rotation systems. Cassava roots penetrated to only 0.5 m deep and extended 1 to 2 m in a horizontal direction depending on the planting density. These results lead to the conclusion that the proposed cassava cropping system would be the most beneficial in terms of economy and control of soil erosion.     

Restoring the Land Productivity of Eroded Land through Soil Water Conservation and Improved Fertilizer Application on Pothwar plateau in Punjab Province,Pakistan

Abstract

Crop production in a rainfed area is constrained by inappropriate management of soil and water by the resource-poor farmers. The present study addresses this issue through integration of practices for soil water conservation (SWC) and soil fertility enhancement as well. Extensive experimentation on wheat-maize was undertaken for two years (2004?2006) on the fields of eight farmers representing two soil types; Rajar (Typic Ustorthent; USDA soil taxonomy) and Guliana (Udic Haplustalf; USDA soil taxonomy) in the Gujar Khan Tehsil of Rawalpindi District, Pakistan. Four treatments consisting of: no SWC +farmer’s rate of fertilizer application (FP), no SWC+improved fertilizer application (IF), SWC practices i.e., deep plowing, bund improvement, plowing across contour+FP (SWC+FP) and SWC+IF. Wheat and maize grain yields in SWC and IF were statistically higher than in the treatments with no SWC and FP, respectively. Compared with the control without any treatment, increase in water use efficiency of both maize and wheat crop was higher in SWC+IF followed by IF alone. On the average, Guliana soil series showed better response to all treatments than Rajar soil. The integrated application of SWC and IF practices increased crop yields in the rainfed area.     

Macropores regulate CO<Subscript>2</Subscript> behavior in an andisol soil

Macropores resulting from soil pedogenesis, biological activity, and agricultural practices play important roles in soil water, chemical and gas transport; however, seldom studies focus on the effect of soil macropores on CO₂ behavior. In this study, a 150-day soil column incubation experiment was conducted to investigate the CO₂ behavior in a homogeneous soil column and a soil column with an artificial macropore, which have the same total porosity. The results showed that the cumulative CO₂ fluxes observed in the soil with a macropore (57.2 g m^?2) were higher than those in the homogeneous soil (52.7 g m^?2). The soil cumulative CO₂ fluxes measured using column incubation can fit the kinetic model, and a higher carbon mineralization rate in the soil with the macropore was found. The results of the incubation experiment also suggest that macropore increased the gas diffusivities, and thus decreased the CO₂ concentrations in the soil profile. This study proposed a simulation experiment and quantified the effect of macropore on soil CO₂ behavior, which could help to understand the mechanism of CO₂ emission from soil with macropores especially caused by agricultural practices.     

Assessment and mapping of soil erosion risk by water in Tunisia using time series MODIS data

Soil erosion by water is a common environmental problem which can affect the sustainable development and the agriculture of developing countries especially. Therefore, several countries, threatened by this phenomenon, adopt different measures to preserve and protect their natural resources. The main purpose of this study was to identify vulnerable areas to establish a soil erosion risk map in Tunisia. In order to do so, an approach based on a combination of the Revised Universal Soil Loss Equation (RUSLE) as an erosion model, Geographic Information System (GIS) and Remote Sensing was applied. RUSLE, which is a model to predict soil loss, is composed of five factors. Erosivity factor (R factor), erodibility factor (K factor), topography factor (LS factor), crop management factor (C factor), and supporting practices factor (P factor). Furthermore, in order to get the most accurate C factor for each land use, times series Moderate Resolution Imaging Spectroradiometer Enhanced Vegetation index (MODIS-EVI) were used. MODIS-EVI time series was helpful for distinguishing vegetation dynamics with taking into account phenological variation of the crops. The results indicated that Tunisia has a serious risk of soil erosion. Indeed, about 24.57% of our study area had a soil loss rate more than 30 t/ha. In these areas, suitable and urgent measures and treatments should be required. Finally, this approach which is based on remote sensing techniques, GIS and erosion model can be useful for planning appropriate environmental decision-making policy in a global scale.     

Influence of paddy rice terraces on soil erosion of a small watershed in a hilly area of Northern Vietnam

Soil erosion is the main cause of soil degradation in northern Vietnam. In this study, soil erosion was measured in 2 m² field plots, a 19.1-ha sub-watershed, and a 248.9-ha main watershed in Tam Quan commune, Tam Duong district, northern Vietnam during 2 years, i.e., 2004–2005. The main watershed includes lowland paddy fields, and is representative for watersheds in the northern Vietnamese landscape. Soil erosion was measured for eight events, at all the three scales to increase our understanding of erosional processes and to assess the effects of paddy fields within the main watershed. The results show that total discharge and sediment yield in both sub-watershed and main watershed were much lower than those in the field plots. Total discharge per unit area in the main watershed was higher than in the sub-watershed, because during the growing season, the paddies are filled with water and any rainfall on them therefore becomes runoff. Sediment yield in the main watershed fluctuated, depending on the soil erosion contribution from many sub-watersheds. Annual rainfalls in 2004 and 2005 were 1,172 and 1,560 mm, respectively, resulting in corresponding total discharges of 54 and 332 mm and total soil losses of 163 and 1,722 kg ha^?1 year^?1. High runoff volumes occurred in July, August, and September, but April, June, the last 10 days of September and October, were the susceptible periods for soil erosion in the study area because of low plant cover and many agricultural activities during these periods.     

Long-Term Changes in the Soil Properties and the Soil Macrofauna and Mesofauna of an Agricultural Field in Northern Japan During Transition from Chemical-Intensive Farming to Nature Farming

Summary

This paper reports the changes in soil chemical and physical properties, and in the populations and diversity of the soil macrofauna and mesofauna that occurred during the 10 years (1976-1986) following the initiation of nature farming practices on this once chemically-managed field in Northern Japan.     

Implications of Elevated CO2-Induced Changes in Agroecosystem Productivity

SUMMARY

Since CO₂ is a primary input for crop growth, there is interest in how increasing atmospheric CO₂ will affect crop productivity and alter cropping system management. Effects of elevated CO₂ on grain and residue production will be influenced by crop selection. This field study evaluated soybean [C₃; Glycine max(L.) Merr.] and grain sorghum [C₄; Sorghum bicolor (L.) Moench.] cropping systems managed under conservation tillage practices and two atmospheric CO₂ concentrations (ambient and twice ambient) for three growing seasons. Elevated CO₂ increased soybean and sorghum yield by 53% and 17% increase, respectively; reductions in whole plant water use were also greater for soybean than sorghum. These findings suggest that increasing CO₂ could improve future food security, especially in soybean production systems. Elevated CO₂ increased aboveground residue production by > 35% for both crops; such shifts could complement conservation management by increasing soil surface cover, thereby reducing soil erosion. However, increased residue could negatively impact crop stand establishment and implement effectiveness during tillage operations. Elevated CO₂ increased total belowground dry weight for both crops; increased root proliferation may alter soil structural characteristics (e.g., due to increased number and extent of root channels) which could lead to increases in porosity, infiltration rates, and subsequent soil water storage. Nitrate leaching was reduced during the growing season (due to increased N capture by high CO₂-grown crops), and also during the fallow period (likely a result of altered decomposition patterns due to increased C:N ratios of the high CO₂-grown material). Enhanced crop growth (both above-and be-lowground) under elevated CO₂ suggests greater delivery of C to soil, more soil surface residue, and greater percent ground coverage which could reduce soil C losses, increase soil C storage, and help ameliorate the rise in atmospheric CO₂. Results from this study suggests that the biodegradability of crop residues and soil C storage may not only be affected by the environment they were produced in but may also be species dependent. To more fully elucidate the relationships between crop productivity, nutrient cycling, and decomposition of plant materials produced in elevated CO₂ environments, future studies must address species effects (including use of genetically modified crops) and must also consider other factors such as cover crops, crop rotations, soil series, tillage practices, weed management, and regional climatic differences.     

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.     

Mycorrhizal Associations and Their Manipulation for Long-Term Agricultural Stability and Productivity

Summary

Mycorrhizae refer to an association (largely symbiotic) between plants and fungi that colonize the cortical root tissue of most agricultural crops during the period of active plant growth. The contribution of these symbioses to plant growth and soil fertility maintenance has been well-recognized for past several years. In spite of these benefits to agriculture, at present, the realization of the full potential of these fungi has not yet been reached. It must also be recognized that recent research on the possible application of the mycorrhizal symbiosis in agriculture has revealed many gaps in knowledge of fungal biology and ecology. Scientific knowledge on the role of these fungi in plant development and protection, soil stabilization, aggregate formation and creation of nutrient reserves is still limited. For efficient use and manipulation of these fungal symbioses for long-term agricultural stability and productivity, our understanding of their physiology, function and interactions with existing crops and environmental conditions should be improved. Besides, effects of different agronomic practices, application of chemical fertilizers and pesticides on their ecology and function should be elucidated before their successful utilization in agriculture.

This paper presents information on the morphology of different my-corrhizal fungi, their physiology and functions. Methods presently used to produce mycorrhizal inocula, their application in the field, problems to be resolved for their massive exploitation and future research needs have also been described. References have been selected to explain the recent advances in our understanding on these beneficial fungi.