Integrated Cropping Systems Research Articles

Organic and Conventional Production Systems in the Wisconsin Integrated Cropping Systems Trial: III. Yield Trends

The Wisconsin Integrated Cropping Systems Trial (WICST) at Arlington, WI, compared five production philosophies in place of fixed treatments, which can be problematic, during 1990 to 2012. Corn (Zea mays L.) was the test crop common to the five cropping systems. All five cropping systems produced positive, average corn yield trends ranging from 0.1 to 0.2 Mg ha−1 yr−1. The overall rates in three conventional systems exceeded those in two organic systems; but the systems nearly equalized when better technology was introduced in the organic systems. Genetic engineering did not accelerate yield improvements. Hence the difference between conventional and organic systems has been largely due to the available technology, not agroecological factors. The yield advantage for corn following alfalfa (Medicago sativa L.) vs. continuous corn (the rotation effect) was 1.47 ± 0.38 Mg ha−1 with no linear or quadratic trends and with the largest values occurring in years with stresses that hindered corn development. Although all five cropping systems produced positive yield trends across two decades, that did not prove they were sustainable over the longer term. There was no clear advantage for either organic or conventional systems in regard to sustainability so the selection process should tailor the cropping system to the individual farm. The resulting picture is a dynamic agriculture with each cropping system encountering and solving challenges. Furthermore, it shows the benefits of long‐term, cropping systems trials in providing base line data, monitoring time‐trends, evaluating new technology, and examining sustainability issues.

Cropping system intensification grading using an agro-environmental indicator set in northern Italy

The term agro-environmental sustainability in agriculture usually refers to farming intensity. Lower intensity farming can be managed by reducing chemical and energy inputs. Beyond ethical issues and having in mind only agronomic aspects, cropping systems are defined by regulations that classify them according to their different input levels as conventional (most intensive), integrated (intermediate intensity), and organic (least intensive).Among organic cropping systems, it is expected that the most intense cropping level would be arable farms where there is a greater need to import input factors, and the least intense level would be livestock farms. This research aims to systematically grade conventional, integrated, and organic cropping systems using a set of 22 indicators of input and environmental pressure. The grading results will then be compared to regulation-defined intensities.Eight cropping systems belonging to four intensification levels were analysed by an indicator set classified as driving force or pressure indicators per the DPSIR schema. Driving forces represented farmer management decisions; pressures represented stressors to the environment resulting from agricultural activities not directly modifiable by the farmer. The 22 indicators analyse five aspects of cropping system: land use, fertiliser use, pesticide use, energy use and gaseous emissions.Study results showed that most indicators were able to accurately grade the cropping system intensities. Specific driving forces and pressures indicators that failed to grade the cropping systems as expected related to several explainable factors. For driving force indicators, conventional systems demonstrated the highest impact on the environment and arable organic cropping systems the lowest. For pressure indicators, conventional cropping system presented the highest impact, followed by integrated cropping systems. In this case the arable organic cropping system presented a higher impact than did the livestock organic system. This level of discrimination showed that pressure indicators performed better at grading system intensification than did driving force indicators.As a consequence, the analysis showed that higher input levels do not always result in higher pressures on the environment. Therefore, the environment would be better served by regulations that set thresholds for pressures rather than system inputs. The results also underlined that practices such as manure use and meadow presence improve the environmental performances of cropping systems.

Green Bean under Organic and Integrated Crop Systems in a Mediterranean Area Greenhouse: Effects on Dry Matter and Nutrient-Extraction Distribution Pattern

The experiment was conducted in two polyethylene greenhouses located in Almería (Spain) with Mantra green bean crop (Phaseolus vulgaris ssp. volubilis), on a sand-mulched loam soil with trickle irrigation. The experimental design was two factorial with four replications per treatment. The treatments applied were two crop systems, organic (OCS) and integrated (ICS), and two organic-matter levels of soil, 1.0% (low organic-matter soil, LOMS) and 2.5% (high organic-matter soil, HOMS). Nitrogen (N) and potassium (K) were applied by fertigation, and total levels were 68 kg N ha−1 and 107 kg K ha−1 following Regulation (CEE) 2092/91 (Organic Crop System) and Specific Regulation of the Junta of Andalusia (Spain) BOJA 10/01(Green Bean Integrated Crop Production). Total N, phosphorus (P), K, calcium (Ca), and magnesium (Mg) were determined in different plant fractions (fruit, leaf, and stem). Nutrient extraction by plant was significantly greater under ICS (111 kg N ha−1, 36 kg P ha−1, 130 kg K ha−1, 96 kg Ca ha−1, and 30 kg Mg ha−1) than under OCS (78 kg N ha−1, 22 kg P ha−1, 83 kg K ha−1, 71 kg Ca ha−1, and 22 kg Mg ha−1). Extracted nutrient levels did not show significant differences between organic-matter treatments. Nutrient-use efficiency was similar under all treatments. Also the N and Ca patterns between organs were unaffected by treatments, but P, K, and Mg distribution patterns among organs were affected by treatments. In general, N fruit and leaf extractions were similar (around 40%) and greater than N stem. Phosphorus leaf extraction was greater than in stem and fruit. Calcium and Mg extractions were the greatest in leaf (70% and 50%), intermediate in stem (20% and 30%), and the lowest in fruit (10% and 20%). Potassium fruit extraction under ICS was significantly greater (39%) than OCS (35%), whereas K stem extraction under OCS was greater (40%). Similar distribution patterns were found for organic-matter level. Potassium fruit extraction under HOMS was greater, whereas K stem extraction was greater under LOMS.

Midwest Cropping System Effects on Soil Properties and on a Soil Quality Index

Cropping systems may improve or decrease soil quality depending on the specific crop rotation, nutrient amendments, and tillage practices employed. We conducted this study to determine the effect of six cropping systems in the Wisconsin Integrated Cropping Systems Trial on soil properties after 18 yr of continuous treatments. We sampled soils (0–5 cm and 5–20 cm depths) following the corn (Zea mays L.) year of three grain‐based systems (continuous corn and two grain rotations), after both corn and alfalfa (Medicago sativa L.) in two forage‐based systems (organic and conventional), and in grass–legume pasture. Extractable P and K, pH, total organic carbon (TOC), total N, active soil C, potentially mineralizable nitrogen (PMN), water‐stable aggregates (WSA), bulk density (BD), penetrometer resistance, and total microbial biomass (TMB) were measured, and the Soil Management Assessment Framework (SMAF) soil quality index (SQI) was determined. The pasture (0–5 cm) was significantly better than all other systems in almost all soil quality indicators and had the highest SQI (96 vs. mean of 87 for others). The alfalfa‐based systems had more total N, TOC, active C, PMN, and WSA and higher BD in one or both depths than did the grain‐based systems but SQIs were not different. Among the grain systems, there was less variation and few significant differences were observed. While there were significant differences among systems for most soil properties, a SQI based on a composite of seven soil properties, showed few differences on this well managed, productive, prairie‐derived soil.

Arable land use intensity change in China from 1985 to 2005: evidence from integrated cropping systems and agro economic analysis

SUMMARYA cropping system is the consequence of environmental and socio-economic conditions that determine the intensity of agricultural land use. Accurate information on regional land use intensity and changes in land use intensity is important for food security and sustainable resource management in China. Therefore, a better understanding of the spatial and temporal changes in arable land use intensity (ALUI) based on the cropping system used is essential to comprehend the changes in land use and the sustainability of the food system. The purpose of the present study was to investigate the spatial difference in ALUI and how it has changed in China by comparing data on cropping systems from 1985 and 2005. The basic cropping system data were acquired from the 1985 reference book and the 2005 national land use investigation. The ALUI was defined by the application of inputs (irrigation water and fertilizer) to arable land and the duration of disturbances (the duration of cultivation and the frequency of cropping), and it was calculated using the information entropy approach at the cropping region scale (cropping region being defined by the geographical and climatic conditions at the beginning of the 1980s). Spatial and temporal changes in the ALUI in China over the past two decades were observed and analysed. The results indicated a clear pattern in ALUI, increasing from the north to the south in 2005. Furthermore, the ALUI significantly increased after the 1980s, but the rate of increase was lower in the south than in the north. The most intensive land use in 1985 was in the area of the lower reach of the Yangtze and Huai Rivers, and it expanded northwards towards the Huang-Huai-Hai plain in 2005. The large increase in intensity in the northern single-cropping regions was strongly associated with a rapid increase in inputs and longer duration of cultivation. Decreases in duration of cultivation and planting area helped slow the ALUI increase in multiple cropping regions, which were concentrated in coastal and economically developed regions where more fertile soil and suitable climates existed, allowing the growth of multiple crops. These results suggested that a decrease in the planting area and a slow increase in the ALUI in the lower reaches of the Yangtze River, South China, Southeast China and Northeast China should be of concern, but land use in some western regions should maintain the land production capacity to build sustainable cropping. In the future, it will be necessary to produce more food in a more sustainable way.

Long-term effects of organic, conventional, and integrated crop systems on Carabids

One of the main aims of sustainable agriculture is to reduce the risk of disease in cropping systems and thereby contribute to preserving public health and conserving the environment. In particular, if we are to reduce our recourse to agrochemicals, we need to acquire a deeper understanding of ecological processes, for instance biological pest control by predatory arthropods such as Carabids. We analyzed the population dynamics of a carabid (Pterostichus melanarius) in various cropping systems (conventional, integrated, and organic) to improve our limited knowledge of its potential impact on insect populations. To do this, we built a model composed of three coupled modules, each referring to different assumptions: a phenology module of the carabid species was based on a periodic Leslie-matrix model and a 1:1 sex ratio, the population was spatialized in Brittany (Western France) using a spatially implicit landscape module that simulated the capacity of grass margins to provide shelter for this carabid beetle, and an agronomic module was used to assess the effects of different crop management systems on the beetle population. Our results showed that the spread of P. melanarius larvae by farming practices was key to species presence in crop fields. This was greatly dependent upon the farming calendar, the intensity of farming practices, and the presence of shelter zones. Maintaining and managing uncultivated habitats such as grass margins is thus as crucial for this beneficial predator as managing cultivated fields (asymptotic growth of the population was found to be 25% higher in integrated and organic management systems when 20% grass margins were present). At the field level, integrated management and direct drilling (with minimum disruption of the soil surface) are the best crop management systems for P. melanarius survival. Organic management is less effective (asymptotic growth of the population is only half that of integrated and direct-drilling management systems), for it requires multiple soil tilling to compensate for the absence of herbicides. Winter oilseed rape is the most detrimental crop (asymptotic growth of the population is half that seen with other crops), as it gives rise to summer molluscicides and soil tillage. This is the first study developing a numerical model of the long-term effects of landscape composition and cropping system on this beneficial predator species. This approach provides a powerful tool to test hypotheses and quantify their possible effects in agroecology.

Integrated Weed Management Systems Identified for Jointed Goatgrass (Aegilops cylindrica) in the Pacific Northwest

Jointed goatgrass is an invasive winter annual grass weed that is a particular problem in the low to intermediate rainfall zones of the Pacific Northwest (PNW). For the most part, single-component research has been the focus of previous jointed goatgrass studies. In 1996, an integrated cropping systems study for the management of jointed goatgrass was initiated in Washington, Idaho, and Oregon in the traditional winter wheat (WW)–fallow (F) region of the PNW. The study evaluated eight integrated weed management (IWM) systems that included combinations of either a one-time stubble burn (B) or a no-burn (NB) treatment, a rotation of either WW–F–WW or spring wheat (SW)–F–WW, and either a standard (S) or an integrated (I) practice of planting winter wheat. This study is the first, to our knowledge, to evaluate and identify complete IWM systems for jointed goatgrass control in winter wheat. At the Idaho location, in a very low weed density, no IWM system was identified that consistently had the highest yield, reduced grain dockage, and reduced weed densities. However, successful IWM systems for jointed goatgrass management were identified as weed populations increased. At the Washington location, in a moderate population of jointed goatgrass, the best IWM system based on the above responses was the B:SW–F–WW:S system. At the Washington site, this system was better than the integrated planting system because the competitive winter wheat variety did not perform well in drought conditions during the second year of winter wheat. At the Oregon site, a location with a high weed density, the system B:SW–F–WW:I produced consistently higher grain yields, reduced grain dockage, and reduced jointed goatgrass densities. These integrated systems, if adopted by PNW growers in the wheat–fallow area, would increase farm profits by decreasing dockage, decreasing farm inputs, and reducing herbicide resistance in jointed goatgrass.

Organic and Conventional Production Systems in the Wisconsin Integrated Cropping Systems Trial: II. Economic and Risk Analysis 1993–2006

This article, the second in a series looking at the Wisconsin Integrated Cropping Systems Trial (WICST), reports on the profitability of six conventional and organic systems, with a focus on net returns and associated risk exposure. Several pricing scenarios were compared to evaluate the impact of government programs and organic price premiums. When net return estimates are made using only neighboring elevator prices (no government programs or organic price premiums), we found that the no‐till corn‐soybean system [Zea mays L. and Glycine max (L.) Merr.] was the most profitable grain system, and management intensive rotational grazing (MIRG) the most profitable forage system. When government programs and organic price premiums are included, returns increased by 85 to 110% for the organic grain system (corn‐soybean‐wheat + red clover (Triticum aestivum L. + Trifolium pratense L.) and 35 to 40% for the organic forage system [companion seeded alfalfa with oat + field pea (Medicago sativa L., Avena sativa L., and Pisum sativum L.), hay, and then corn]. This places both organic systems with higher returns than any of the Midwestern standards of no‐till corn‐soybean, continuous corn, or intensive alfalfa production. Also, the results indicate how risk exposure varied across systems. Interestingly, taking risk into consideration did not drastically affect the ranking among those systems. Our analysis shows that, under the market scenarios that prevailed between 1993 and 2006, intensive rotational grazing and organic grain and forage systems were the most profitable systems on highly productive land in southern Wisconsin.

Organic and Conventional Production Systems in the Wisconsin Integrated Cropping Systems Trials: I. Productivity 1990–2002

During the last half‐century, agriculture in the upper U.S. Midwest has changed from limited‐input, integrated grain–livestock systems to primarily high‐input specialized livestock or grain systems. This trend has spawned a debate regarding which cropping systems are more sustainable and led to the question: can diverse, low‐input cropping systems (organic systems) be as productive as conventional systems? To answer this question, we compared six cropping systems ranging from diverse, organic systems to less diverse conventional systems conducted at two sites in southern Wisconsin. The results of 13 yr at one location and 8 yr at the other showed that: (i) organic forage crops can yield both as much dry matter as their conventional counterparts and with quality sufficient to produce as much milk; and (ii) organic corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and winter wheat (Triticum aestivum L.) can produce 90% as well as their conventionally managed counterparts. The average yields for corn and soybean, however, masked a dichotomy in productivity. Combining Wisconsin Integrated Cropping Systems Trial (WICST) data with other published reports revealed that in 34% of the site‐years, weed control was such a problem, mostly due to wet spring weather reducing the effectiveness of mechanical weed control techniques, that the relative yields of low‐input corn and soybean were only 74% of conventional systems. However, in the other 66% of the cases, where mechanical weed control was effective, the relative yield of the low‐input crops was 99% of conventional systems. Our findings indicate that diverse, low‐input cropping systems can be as productive per unit of land as conventional systems.

Ongoing Development of Integrated Weed Management Systems on the Canadian Prairies

Herbicides are very effective tools to control weeds but there has been an overreliance on their use at the expense of other useful methods of weed management. Farmers are interested in alternative methods of weed management but are concerned about the risk of adopting such practices with current small profit margins. Research on the Canadian Prairies has found that cropping systems that utilize zero tillage, diverse crop rotations, competitive cultivars, higher crop seed rates, specific fertilizer management, and cover crops can effectively manage weed populations, especially when used in conjunction with targeted but limited use of herbicides. Farmers are gaining confidence in the merits of such agronomic practices in terms of sustainable weed management and are gradually adopting these integrated cropping systems on their farms. Further research and extension efforts are required to ensure that these integrated weed management systems are biologically and economically robust to facilitate greater adoption at the farm level.

Organic and Conventional Production Systems in the Wisconsin Integrated Cropping Systems Trials: I. Productivity 1990–2002

During the last half-century, agriculture in the upper U.S. Midwest has changed from limited-input, integrated grain–livestock systems to primarily high-input specialized livestock or grain systems. This trend has spawned a debate regarding which cropping systems are more sustainable and led to the question: can diverse, low-input cropping systems (organic systems) be as productive as conventional systems? To answer this question, we compared six cropping systems ranging from diverse, organic systems to less diverse conventional systems conducted at two sites in southern Wisconsin. The results of 13 yr at one location and 8 yr at the other showed that: (i) organic forage crops can yield both as much dry matter as their conventional counterparts and with quality sufficient to produce as much milk; and (ii) organic corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and winter wheat (Triticum aestivum L.) can produce 90% as well as their conventionally managed counterparts. The average yields for corn and soybean, however, masked a dichotomy in productivity. Combining Wisconsin Integrated Cropping Systems Trial (WICST) data with other published reports revealed that in 34% of the site-years, weed control was such a problem, mostly due to wet spring weather reducing the effectiveness of mechanical weed control techniques, that the relative yields of low-input corn and soybean were only 74% of conventional systems. However, in the other 66% of the cases, where mechanical weed control was effective, the relative yield of the low-input crops was 99% of conventional systems. Our findings indicate that diverse, low-input cropping systems can be as productive per unit of land as conventional systems.

Organic N and particulate organic matter fractions in organic and conventional farming systems with a history of manure application

Indicators of soil fertility are needed for the effective management of organic farming systems. Sustainable management hinges upon our gaining an improved understanding of C and N dynamics. The influence of cropping systems and amendments applied in the Lakeland Wisconsin Integrated Cropping Systems Trial on total hydrolyzable organic N (THN) fractions and particulate organic matter (POM) was investigated after a decade in a conventional cash grain system (Conv) of continuous maize amended with inorganic fertilizer, an organic cash-grain system (Org-CG) that relied on legume N, and an organic animal-based system (Org-AN) that included alfalfa and manure additions. Maize yields had consistently ranked Org-CG Org-CG > Conv. Amino sugar-N (AS-N) contents, which reflect microbially derived N, did not differ among systems and concentrations were quite high (346.5 mg AS-N/kg soil in the 0–50 cm depth). This, and soil variability were attributed to the sites’ history of manure application. The amount (1.3 g POM-C/kg soil) and proportion (≈7.5% of total SOC) of POM-C were quite low and did not differ among systems. Failure to accumulate SOC or POM in these soils, even under organic management, is attributed to rapid C decay and/or limited root growth. An N rate study was added the fall before samples were taken and N addition did increase yield in the Conv and Org-CG systems despite evidence of soil N surplus. This suggests that either amino N is unavailable to plants or that root N acquisition is limited by other constraints. Low POM-C contents accompanied by high AS-N and AA-N levels reveal an imbalance in these soils which are likely to be C limited. Based on this, we conclude excess N has prevented use of organic practices from enhancing soil quality at this site.

Water Quality Simulation of Rice/Crawfish Field Ponds within Annualized AGNPS

Rice and crawfish are important agricultural commodities in Louisiana and they are often managed as integrated cropping systems. The effluent from rice/crawfish ponds is an environmental concern because of potentially high sediment and nutrient concentrations. However, current available models used for TMDL development such as BASIN, SWAT, and AnnAGNPS do not have the capability of simulating rice/crawfish farming and their impact on water quality. The objective of this study was to develop a rice/crawfish module which can be integrated into the Annualized Agricultural Non-point Source Pollution (AnnAGNPS) model to simulate rice/crawfish farming and its impact on water quality. Both hydrologic and pollutant mass balances are maintained for the crawfish ponds in AnnAGNPS. Inflows, outflows, precipitation, infiltration (or seepage), and evaporation (or evapotranspiration) are considered for hydrologic mass balance. Water release from the pond is added to the receiving reach of the AnnAGNPS cell in which the rice/crawfish pond is located. Pollutant mass balances are maintained based on the inflows and outflows to the crawfish pond and water quality characteristics of the flows. The dynamics of complicated nutrient reactions in the pond are not considered at this development stage. Water quality constituents considered in the model are suspended sediment, total nitrogen, total phosphorus, dissolved nitrogen, and dissolved phosphorus. Based on a detailed review of rice/crawfish management practices and their impact on water quality, a water quality database of rice/crawfish ponds has been built into AnnAGNPS and a user interface was designed to quantify the rice/crawfish farming processes. This water quality database provides an estimate of water quality in the crawfish pond effluent during simulations, and a more accurate quantification of effluent water quality can be achieved through analysis of water samples of the water released from the pond. Model testing of proof of concept showed that the model performed appropriately and provided logical results.

Evaluation of Learning Group Approaches for Fostering Integrated Cropping Systems Management

Cropping systems management requires integration of multiple forms of knowledge, practice, and learning by farmers, extension educators, and researchers. We evaluated the outcomes of participation in collaborative learning groups organized to address cropping systems and, specifically, challenges of integrated weed management. Groups were constituted to focus on two different cropping systems: fresh-market vegetables and soybean [Glycine max (L.) Merr.] (both in rotation with other crops). Participants in the learning groups included farmers (representing a wide array of production philosophies), extension educators, and university faculty with extension, resident instruction, and research responsibilities. Interviews were conducted to assess the value of the learning groups and how they influenced participants to alter practices in support of integrated crop and weed management. Farmer participants reported an increased capacity to implement integrated approaches to management, resulting in part from changes in self-esteem, enhanced decisionmaking capabilities, and increased awareness of available resources. Extension educators reported that learning group participation increased their ability to use facilitative education methods. University research and teaching faculty also noted enhanced effectiveness from participation in the learning group project. Evidence was obtained that learning groups foster knowledge creation and transformational learning and that they can be more effective than conventional (lecture-based) approaches for achieving such outcomes.

Use of glufosinate-ammonium to control cruciferous weed species in glufosinate-resistant winter oilseed rape

Weed control is an important component of integrated cropping systems. However, cruciferous weeds are difficult to control in conventional winter oilseed rape ( Brassica napus L.) and new herbicide options are needed. The aim of this study was to determine the potential for use of glufosinate-ammonium (2-amino-4-(hydroxymethyl-phosphinyl)-butanoic acid) as a flexible post-emergence herbicide for control of cruciferous weeds in glufosinate-resistant winter oilseed rape in the Hercynian dry region of Central Germany. The effects of glufosinate-ammonium (900 g active ingredients ha −1) on chlorophyll fluorescence and dry matter in 4-week-old Sisymbrium loeselii L. (tall hedge mustard), S. officinale (L.) Scop. (hedge mustard), S. altissimum L. (tall tumble mustard), and Descurainia sophia (L.) Webb ex Prantl (flixweed) were assessed under controlled conditions in a growth room. A 2-year field trial was used to investigate the effect of glufosinate-ammonium on the dry matter of S. loeselii. Therefore, different application times (two- to four-leaf stage, five- to six-leaf stage, end of vegetative period in autumn, beginning of vegetative period in spring) and herbicide rates (450 and 900 g a.i. ha −1) were tested. Under controlled growth room conditions, plants of all four cruciferous weed species showed a gradual decrease in the quantum yield of photosystem II. The quantum yield was less than 20% of the control plants measured from 0 to 34 h after application. Dry matter production of all four species was reduced to less than 3% that of the untreated control 4 weeks after application. Under field conditions, dry matter production of S. loeselii varied in dependence on the environmental conditions and was 0–88% of the control plants. Under controlled and field conditions, the results indicate that glufosinate-ammonium is effective in post-emergence control of the tested cruciferous weeds in glufosinate-resistant winter oilseed rape. Under field conditions, weather and crop growth influenced herbicide effectiveness.

Effects of seed production and storage conditions on blackgrass (Alopecurus myosuroides) germination and shoot elongation

Blackgrass is a common winter annual grass weed in autumn-sown crop rotations in Atlantic European countries. Control with a minimum amount of herbicides in integrated cropping systems would be facilitated by modeling the effect of cropping systems on its demography. To develop the submodel relating weed seed bank to emerged seedlings, laboratory experiments were conducted to analyze and quantify seed germination and shoot elongation. These processes were studied as a function of environmental conditions during seed production (nitrogen availability, water deficit, plant density, and crop) and of seed characteristics (seed weight, harvest date, storage length, and dry-stored/soil-buried). Nonlinear equations relating germination and shoot elongation to time calculated as cumulated degree-days were fitted to the observed germination and shoot elongation data. These were used to estimate parameters for germination proportion and rate, as well as final shoot length and elongation rate. Recently harvested seeds germinated best and fastest when they were collected in spring crops compared with winter crops. Germination proportion and rate increased with seed storage length, especially for seeds collected in winter crops. Midgermination time decreased with seed weight and water deficit during seed production; it increased with nitrogen amounts available to the mother plants. Maximum shoot length increased with seed weight and plant density during seed production. It decreased with nitrogen availability to mother plants and with storage length, irrespective of whether the seeds were dry-stored or buried in soil. Elongation rate was highest for early- and fast-germinating seeds. Time to midelongation increased with maximum shoot length. These germination and preemergence growth models can now be combined with other submodels to develop a blackgrass emergence model.

The effect of farming systems on the relationship of corn root growth to grain yields

AbstractThe Wisconsin Integrated Cropping Systems Trial has been comparing different farming systems on two farm sites in southern Wisconsin since 1989. Inexplicable differences in the yields of corn grown in three systems stimulated research on the relationship between yield and the dynamics of root growth. The three systems were continuous corn with mineral fertilizer (CS1), corn—soybean—winter wheat—red clover (CS3), and corn—oat + alfalfa—alfalfa with dairy manure applied (CS5). Four or five sequential root samplings were taken each growing season on two sites for 3 years. Soil monoliths were taken from around the base of the plant and washed out over a 1-mm sieve. Estimates were obtained of the length and health of roots from different nodes that were attached to the crown of the plant. The seasonal accumulation of root length was estimated by summing the maximal root length produced at each root node. Corn grown in monoculture averaged 7.5 Mg of grain/ha, which was similar to corn grown after red clover green manure (7.3 Mg/ha) but less than corn grown after alfalfa with manure (8.5 Mg/ha). Contrary to expectations, corn grown in monoculture averaged 26% more root length over the season than CS3 and 12% more length than CS5. The differences were mostly due to increased production of later sets of roots (nodes 6–9) for the corn in monoculture. However, for the first sets of nodes (seminal—node 5) the percentage of healthy roots was lower in the monoculture system (59%) than in CS3 (63%) or CS5 (76%). The increased root growth associated with corn grown in monoculture may be a response to poor root health. Regressions with root growth accounted for a large amount of the variation in grain yields. Corn grown after alfalfa with manure achieved higher yields with less roots than did corn grown in monoculture. Yields in the former system plateaued at root lengths of 1 cm/cm3 and greater, producing grain yields that ranged from 8 to 10 Mg/ha. Corn grown in CS1 and CS3 showed curvilinear responses with calculated yield maxima of 8.7 and 9.9 Mg/ha at root lengths of 2.12 and 1.74 cm/cm3, respectively. Intensifying the use of rotations and organic manures seemed to increase the ability of the corn rooting system to support grain yields. The cause for this greater efficiency is not yet clear, though root health may be an important factor.

The Oil Mallee Project: A Multifaceted Industrial Ecology Case Study

SummaryThe planting on degraded agricultural lands of eucalypts for leaf oil provides a commercial incentive for restoring original vegetation; a sustainable method of controlling groundwater and salinity; a product that is an environmentally benign substitute for a widely used solvent damaging to the ozone layer; and a mechanism for reducing atmospheric carbon dioxide levels. With integrated tree crop systems and improved harvesting and processing technologies, the Western Australian wheatbelt could produce large volumes of high‐cineole eucalyptus oil from mallee eucalypts. With new industrial markets, a scale of planting could be achieved that would result in substantial land rehabilitation benefits. Industrial solvent markets are large and currently in transition following the recent withdrawal of 1,1,1‐trichloroethane as a result of international measures to control ozone depletion. There is a strong preference in these markets for “natural” replacement products. Although large‐scale penetration of these markets would need prices about half those prevailing in traditional eucalyptus oil markets, this goal should be achievable with the potential for economies of scale, genetic advances, and improved harvesting and processing technologies.

Integrated Cropping Systems—A Multi-discipline Degree

Washington State Univ. Tri-Cities offers a new agricultural degree program titled Integrated Cropping Systems. It is intended to provide a basic education on the fundamentals of crop production and the environmental context in which crops are grown. Courses are offered at the upper division level to interface with the lower division courses offered at local community colleges. The curriculum is composed of courses in environmental science, ecology and conservation as well as crop growth and development, crop nutrition, plant pathology integrated pest management and others. Students need to meet the same requirements as those at other Washington State Univ. campuses in regards to the general education requirements. The purpose of the Integrated Cropping Systems program is to provide an educational opportunity for agricultural professionals and others in the region who are unable to commute or move to the main campus location. The curriculum provides the background needed for such occupations as grower/producer, crop scouting, sales representative and other entry level agricultural professions. It will supply credits toward certification through the American Registry of Certified Professional Agricultural Consultants (ARCPACS). Integrated Cropping Systems is a unique agricultural curriculum designed to help agriculturists integrate their production practices into the local ecosystem in a way that the environment does not incur damage. It emphasizes the use of environmentally conscience decisionmaking processes and sound resource ethics. The program will graduate individuals who have heightened awareness of the impact agricultural practices have on the ecosystem in which they are conducted.

Designing an Integrated Cropping Systems Research Program

Liberia is short on basic food commodities and a research base on which to build a more productive agriculture. The Central Agricultural Research Institute (CARI) is located in the humid forest zone near Suakoko, Bong County, Liberia, with national responsibility for basic and applied agricultural research. A new initiative will integrate technical research disciplines with extention workers and farmers into an effective cropping systems research (CSR) and outreach effort. The objective is to shift the focus away from disciplines and the experimental stations and to incorporate appropriate component technologies into sustainable, environmentally sound, and economically viable prototype systems that can be tested on farms. These technologies and systems will be studied by scientists and farmers using on-farm research, validated in additional sites by extension workers and farmers. The process involves setting clear short- and long-term goals in the institute, and elaborating a program design within the Lib...