No full-text available
To read the full-text of this research,
you can request a copy directly from the author.
Strategies for research and management in reduced-input agroecosystems
Abstract
Developing reduced-input agroecosystems is a challenge to researchers and practitioners in a number of disciplines. In particular, because of the complexity of managerial inputs, understanding the effects of decreases in levels of one or several inputs presents a difficult experimental problem. Moderate reductionism is proposed as an appropriate hierarchical analysis, which first characterizes system level behavior and then explains it in terms of system components and their interactions. An example is given using reduced nitrogen fertilizer inputs; higher nitrogen use efficiency at lower levels of input is explained by increased nutrient recycling between soil and plant subsystems. Transition from conventional to reduced-input management involves changes in both economic and ecological properties of agroecosystems. Biological, chemical and physical changes, including increased species diversity, tighter nutrient recycling, and longer-term perennial effects, may parallel ecological succession. Hypothetical trends for several such changes are discussed.
... These laws direct how agroecologists interpret the behaviour of agroecosystems and develop strategies they feel will enhance sustainable production. Resolving problems involves mimicking the functions within natural ecosystems (Hendrix 1987). Put another way, sustainability is most likely to be ensured by employing production practices that promote community stability, optimize the rate of turnover and recycling of organic matter and nutrients, optimize multiple use of the landscape, and optimize energy flow efficiency (Altieri 1987). ...
Given relatively low adoption levels to date, the potential benefits of organic farming systems are not yet very visible. However, there is growing evidence in the literature that adoption of such systems produces multiple environmental, social, and financial benefits that can solve pressing agricultural problems in Canada. Compared with their duration as conventional operations, most organic farms in North America perform better under organic management. This outcome is usually a product of lower input costs, more diversified production and marketing channels, resilience in the face of variable market conditions, higher premiums, and a better capacity to adapt to weather extremes. However, the performance of farming systems including some horticultural and animal production systems, for which our ecological understanding is limited, is still frequently inferior. The data on social impacts are less conclusive, but there is some evidence that when a community has many sustainable (including organic) producers, there are positive shifts in community economic development and social interaction. The reasons appear to be related to the need to hire more labour, the increased demand for local goods and services, and a greater commitment to participation in civic institutions.
... Ces « lois » déterminent comment les agroécologistes interprètent le comportement des agroécosystèmes et les stratégies qui, selon eux, amélioreront la production durable. La résolution des problèmes nécessite l'imitation des fonctions se retrouvant à l'intérieur des écosystèmes naturels 4 . Autrement dit, recourir à des méthodes de production qui a) favorisent la stabilité de la communauté ; b) optimisent le taux de roulement et de recyclage de la matière biologique et des nutriments ; c) optimisent les usages multiples du paysage terrestre ; d) optimisent l'efficacité des transferts d'énergie et ont le plus de chance d'assurer la durabilité. ...
... These "laws" direct how agroecologists interpret the behaviour of agroecosystems and the strategies they feel will enhance sustainable production. Resolving problems involves mimicking the functions within natural ecosystems 15 . Put another way, employing production practices that a) promote community stability; b) optimise the rate of turnover and recycling of organic matter and nutrients; c) optimise multiple use of the landscape; d) optimise energy flow efficiency, are most likely to ensure sustainability 16 . ...
Conventional strawberry (Fragaria ananassa Duch. cv. Chandler) production was compared with production undergoing conversion to certified organic management in a three-year, replicated, on- farm study. Plant vegetative development, measured as leaf number, leaf area, and vegetative biomass, decreased in the organic production system compared to the conventional system. Developmental differences were less significant in the third year of the study. Reproductive development, measured as number of flower buds, open flowers, and immature fruit, as well as total reproductive biomass, was also lower in the organic system. The timing and degree of difference in responses studied varied over the course of the study. The percent of total berries produced which were not marketable was larger in the conventional system in the second and third years of the study. Marketable fruit yield was consistently lower in the organic plots, but the margin of difference decreased over the course of the study from 39% to 28%. However, market conditions resulted in greater returns per hectare in the organic production system.
Multidisciplinary research takes many forms, according to how strongly the disciplines interact and whether the purpose is to address a broader question or to get a better answer to the original question. The appropriate type depends on the purpose of the research, such as developing a new technique, identifying farmers' innovations that deserve further attention, evaluating a production system, or discovering principles on which future systems can be based. Although sustainable agriculture has many characteristics that make multidisciplinary research particularly appropriate, this does not rule out an important role for a single-discipline research. Nor does it imply that multidisciplinary approaches are not also suitable for many other research areas. Some people regard multidisciplinarity as essential for sustainable agriculture research because they consider that prevailing scientific thought is too dominated by reductionism and too lacking in imagination to deal with system-level complexities, especially those that seem to defy common sense. However, we can see from the evolution of several areas of physics, induding quantum mechanics, relativity theory and statistical mechanics, that even within the confines of a single discipline, scientific thought need not be exclusively reductionist and that it can deal with complex, large-scale phenomena even if their behavior is extremely counterintuitive.
Research papers on reduced-chemical agricultural methods published in single-discipline and multidisciplinary journals were compared with other agricultural research with respect to how the work was done and what it covered. Reduced-chemical research did not involve more multidisciplinary collaboration, despite the commonly heard claim that it does. It showed a slight but inconsistent tendency to run for more years and use more sites per study. The production methods it studied showed to some degree the characteristics attributed to reduced-chemical systems, including greater concern with off-farm effects, greater species diversity, a more important role for information and management, and the use of close-grown crops in association with tilled crops. However, this was much truer for the smaller body of research reported in multidisciplinary journals; in many ways, the larger amount of reduced-chemical research reported in single-discipline journals hardly differed from other agricultural research.
In the fifth year of an agricultural conversion experiment in Pennsylvania, we studied the soil biological community under three treatment regimes planted with corn: organic-manure, organic-legume, and a conventional system. The organic treatments consisted of complex crop rotations, cultivations, and organic matter inputs to control pests and maintain soil fertility. The conventional system consisted of a simple corn/soybean rotation with synthetic fertilizer and pesticide inputs. High rates of CO2 evolution (a measure of potential microbial activity) in the organic plots corresponded with high levels of organic matter input. Soil nematodes were most abundant in organic plots, although seasonal patterns differed between the two organic treatments. Soil microarthropods were dominated by fungivorous Prostigmata mites, which reached peak abundance in organic plots two to five months after organic matter incorporation. Oribatid mites, which were rare throughout the study, followed the same pattern of abundance in each treatment and were probably most influenced by tillage disturbances. Predatory Mesostigmata were generally more abundant in organic plots. Surface-dwelling Collembola were abundant briefly in the spring, but soil-dwelling species dominated numerically throughout the cropping season. Spring tillage appeared to have a strong negative effect on earthworm populations in all plots. Small earthworm species became abundant in organic-manure plots during the summer. Larger earthworm species were abundant in organic-legume and conventional plots after the autumn harvest, when crop residues covered the undisturbed soil The systems-level nature of the Conversion Project experiment makes it difficult to identify cause-effect relationships. The data do suggest that organic amendments tend to enhance soil biological activity, while tillage disturbances tend to disrupt the biotic community.
The assumption that the organic matter content of tropical forest soils is oxidized to atmospheric carbon dioxide when these
soils are converted to agricultural use was tested using results of soil surveys in Puerto Rico (1940's, 1960's, and 1980's).
Results showed that under intensive agricultural use, soil carbon in the top 18 cm of soil was about 30–37 Mg/ha, regardless
of climatic conditions. Reduced intensity of agricultural use resulted in an increase of soil carbon in the order of 0.3–0.5
Mg.ha−1. yr−1 over a 40-yr period. Rates of soil carbon accumulation were inversely related to the sand content of soils. The relation
between rates of soil carbon accumulation and climate or soil texture were better defined at higher soil carbon content. Soils
under pasture accumulated soil carbon and often contained similar or greater amounts than adjacent mature forest soils (60–150
Mg/ha in the top 25 or 50 cm). Soils in moist climates exhibited greater variations in soil carbon content with changes in
land use (both in terms of loss and recovery) than did soils in dry climates. However, in all life zones studied, the recovery
of soil carbon after abandonment of agriculture was faster than generally assumed. Low carbon-to-nitrogen ratios suggested
that intensively used soils may be stable in their nutrient retention capacity. The observed resiliency of these soils suggested
that their role as atmospheric carbon sources has been overestimated, while their potential role as atmospheric carbon sinks
has been underestimated.
No-tillage cropping systems and concepts have evolved rapidly since the early 1960s and are attracting attention worldwide. The rapid growth and interest is associated with increasing pressures for food production from a fixed land resource base with degrading effects of erosion, soil compaction and other factors becoming more noticeable. Research programs have provided many answers and identified new technology needed for success of the no-tillage crop production system in the past two decades and this has resulted in a rapid rate of adoption. Farmers played an important role in the early stages· of development of the system and continue to play an important role in its improvement and rapid rate of adoption. This book provides an inventory and assessment of the principles involved in no-tillage concepts and addresses the application of the technology to practical production schemes. Selected authors and contributors have long been associated either in no-tillage research or application. They represent many disciplines interfacing with the complex interactions of soil, plant and environment. Personal obser vations by the authors in many geographic sectors of the world indicate the principles to be valid but application of the principles to be less uniform. The application of no-tillage principles requires considerable modification as variations in soil and/or climatic condi tions are encountered in different regions of the world.
Several short‐term studies of no‐tillage (NT) vs. conventional tillage (CT) have suggested that N availability is lower in NT. Less is known about the long‐term effects of NT on soil processes and N availability. Recent observations of a NT vs. CT experiment, initiated in 1970 on a Maury silt loam (Typic Paleudalfs), are presented here. During the first 9 yr of this study corn ( Zea mays L.) yields with no N fertilizer were consistently greater in CT than NT, but at high N rates yields were approximately equal. Since 1979, there have been no consistent differences between the tillage systems with regard to yield without N or in relative response to N. Inorganic soil N during 1981 and 1982 was usually equal but occasionally greater in NT compared to CT, in contrast to previous observations during the early years of this experiment. Soil N mineralization was estimated in 1982 by a laboratory soil core incubation technique and by observing dilution rates of labeled N added to field microplots. Both of these approaches suggested that N mineralization was at least as great in long‐term NT plots as in long‐term CT plots. We suggest that the lower availability of N frequently observed in NT soils, in some cases can be a transient effect. In this experiment availability of soil N in NT apparently approached that of CT after approximately 10 yr.
Multiple cropping in conjunction with various minimum tillage practices is currently a conspicuous agricultural production method in the southeastern U.S. The objective of this study was to determine the influence of 5 years of various tillage practices on the fertility status of an Ultisol continuously double-cropped to wheat (Triticum aestivum L.) and soybeans (Glycine max L.). The tillage treatments for each fallhpring were: no-tillage/no-tillage, harrow/ho-tillage, conventional tillageho-tillage, no-tillage/conventional tillage, harrow/conventional tillage, conventional tillage/conventional tillage. With no-tillage, soil pH decreased more rapidly with depth than with conventional tillage treatments. Accumulations of Ca, Mg, P, Mn, and Zn occurred in the surface soil with no-tillage treatments, but surface soil K was lower with no-tillage compared to conventional tillage treatments. Organic C and N did not accumulate in the soil surface under no-tillage to the degree reported in other studies. Results indicate that continuous no-tillage results in increased nutrient concentrations in the surface soil with a rapid decrease with depth, while conventional tillage resulted in a more homogeneous soil with respect to soil fertility status
Please view the pdf by using the Full Text (PDF) link under 'View' to the left. Copyright © . .
Crop residues have become an increasingly important renewable natural resource. They can serve to maintain optimum crop production on the nation's severely eroding 45.3 million ha of cropland as well as decrease the increasing cost of synthetic N fertilizer. Conservation tillage technologies have been recently identified as a high priority research need for sustaining agronomic productivity in the humid USA. Three double‐crop tillage systems—spring and fall disking, fall disking, and no‐tillage—were evaluated for 4 years on a Southern Piedmont Ultisol (Cecil sandy loam—a clayey, kaolinitic, thermic Typic Hapludults). These tillage systems were considered conventional (CT), minimum (MT), and continuous no‐till (NT), respectively. Wheat ( Triticum aestivum L.) and grain sorghum [ Sorghum bicolor (L.) Moench] were used in the double‐crop systems as high stover producing as well as medium N fertilizer requiring crops. Six orthogonal N fertilizer rates ranging from 0 to 250 kg ha ⁻¹ were imposed on each tillage system. Both conservation tillage systems (MT and NT) were manageable in the short term (1 or 2 years) and produced significantly more sorghum grain than the conventional system. Grain yields (4 years) and favorable soil fertility status suggest the MT system was the best double‐crop management system in the long range (>2 years). The sum of wheat and sorghum grain yield increased significantly (5.0 to 7.4 Mg ha ⁻¹ year ⁻¹ ) in a linear manner with stover up to 11.5 Mg ha ⁻¹ year ⁻¹ . This suggests some crop use of the 62 kg N ha ⁻¹ year ⁻¹ returned to the land in stovers when N fertilizers were applied at the recommended rate (100 kg N ha ⁻¹ year ⁻¹ ). It appears that N fertilizer rates may be reduced progressively in small quantities for optimum double‐crop yields in longterm conservation tillage systems on Southern Piedmont lands.
“Sustainable agriculture” means many things to different people in agriculture. At least three different definitions of sustainability are available: sustainability as food sufficiency; sustainability as stewardship; and sustainability as community. Since increased human populations will cause demands for food to continue to grow in the foreseeable future, agricultural sustainability needs to be assessed in ways that will incorporate competing definitions. We suggest that analyzing agriculture as a hierarchical system is the appropriate way to incorporate different concepts of sustainability. Using this concept, we propose a hierarchical definition of sustainability. Agronomic sustainability refers to the ability of a tract of land to maintain productivity over a long period of time. Microeconomic sustainability is dependent on the ability of the farm, as the basic economic unit, to stay in business. Ecological sustainability depends on the maintenance of life-support systems provided by non-agricultural and non-industrial segments of a region. Macroeconomic sustainability is controlled by factors such as fiscal policies and interest rates which determine the viability of national agriculture systems. In our view, there are critical constraints to sustainability at different scales of the agricultural hierarchy. We propose that agronomic constraints are most important at the field scale; microeconomic constraints are dominant at the farm scale; ecological constraints override at the watershed or landscape scale; and macroeconomic constraints are foremost at the regional and national scale. In this paper, we describe the actions of these critical constraints, discuss interactions among various hierarchical levels, and propose ways that agricultural researchers and policy makers can integrate the various views of sustainability.
Prior research has shown that an established organic farm can be as profitable as a conventional farm under certain circumstances. However, organic farming systems often require a transition period before they are fully established after a changeover from conventional farming. Yields may decrease and recover only slowly during this transition period and less profitable crop rotations may be required to establish an organic system. Previous studies have ignored the income trend during the transition phase, and comparisons of organic and conventional farms have been faulted for lack of similarity in management and other resources. The study reported here used a multi-year simulation model to investigate the trend in income of a 117-hectare crop-livestock farm in Pennsylvania (called the Kutztown farm) during this transition process. A baseline model of the Kutztown farm under conventional management (CONB) was found to earn an income (returns over cash operating cost) of $61,900. The transitional models developed were an upper-yield case assuming no yield decline during the transition (TRANS) and a lower-yield case assuming severe yield decline in the first year after the change-over from conventional management and a subsequent linear recovery of yields over a three-year period (TRANS-L). Income was found to be severely depressed by a yield decline during the transitional phase. The first year of TRANS-L resulted in a 43% reduction in income. The scenario without a yield decline (TRANS) resulted in a 13% lower income compared to the baseline (CONB) model. Both transitional models led to an established organic situation with stable organic yields and an income of $57,400 or 7% less than under conventional management. It was found to be more profitable to sell the crops and purchase manure than to feed the crops to beef in a fattening enterprise. At small herd sizes (100 head) the reduction in income caused by the feeding operation was moderate ($1,300), but with a larger operation (213 head) the income sacrifice increased tenfold.
Evidence on the experience with techniques and systems involving lower levels of purchased fertilisers and other agrochemicals, concentrate feeds and energy is reviewed. Economic characteristics considered include yields, gross and net margins per hectare, and labour use. Environmental and physical resource aspects include the incidence of pests, diseases and weeds, nutrient balances and leaching, and energy use. Known techniques can, in many cases, substantially reduce the need for external inputs. However, farm management studies tend to indicate lower than average returns to labour in biological husbandry systems and possibly also in integrated systems. It is generally agreed that adverse environmental impacts are less with lower external input systems, but total energy use per unit of output is not necessarily lower.
Effect of no-tillage vs
- Gallaher
Levels and reduction
- Bunge