Joshua L. Posner

The Wisconsin integrated cropping systems trial: Combining agroecology with production agronomy

Two large-scale (25 ha) trials were initiated in 1989 in Wisconsin to compare six alternative production systems regarding productivity, profitability, and environmental impact. The project was designed and is managed by a coalition of farmers, extension agents and research personnel. Deliberations between production-oriented and ecologically oriented team members resulted in a factorial design, with two enterprise types (cash grain and forage-livestock) and three levels of biological complexity. Statistical methods have been used to identify the most efficient plot size, plot shape, and block shape, and the optimal procedures for sampling soil characteristics. A uniformity year was allowed before initiation of the trial, and the start was staggered. We defined treatments as production strategies rather than a specific set of inputs, which led to a more flexible plot management program.

Weed Community Dynamics and Suppression in Tilled and No-Tillage Transitional Organic Winter Rye–Soybean Systems

Abstract Grower adoption of no-tillage (NT) approaches to organic soybean production has been limited, in part because of the perceived risks of ineffective cover crop management and lack of season-long weed suppression. We conducted research in 2008 and 2009 to assess those risks by quantifying the effects of winter rye cover-crop management (tilling, crimping, or mowing), soybean planting date (mid May or early June), and row width (19 or 76 cm) on weed recruitment, emergence patterns, season-long suppression, and late-season weed community composition in transitional organic production systems. The weed plant community consisted largely of summer annual species in each year, with velvetleaf or common lambsquarters as the most abundant species. Seedling recruitment from the soil seedbank varied between years, but velvetleaf recruitment was consistently greater in the tilled rye than in the NT rye treatments. Weed emergence tended to peak early in the season in the tilled rye treatment, but in the NT rye treatments, the peak occurred in mid or late season. More-diverse summer annual and perennial species were associated with the NT rye treatments. Even so, weed suppression (as measured by late-season weed shoot mass) was much greater in crimped or mowed rye NT treatments than it was in the tilled treatment. Weed suppression among NT rye treatments was greater in 19- than in 76-row spacing treatments in each year and was greater for mid May than it was for early June planted soybean in 2009. The NT planting of soybean into standing rye before termination (crimping or mowing) facilitated timely planting of soybean, as well as effective, season-long weed suppression, suggesting that those approaches to rye and weed management are of less risk than those typically perceived by growers. Our results suggest that NT systems in winter rye provide effective weed-management alternatives to the typical tillage-intensive approach for organic soybean production. Nomenclature: Common lambsquarters, Chenopodium album L. CHEAL; velvetleaf, Abutilon theophrasti Medik. ABUTH; cereal rye, Secale cereale L.; soybean, Glycine max (L.) Merr.

Seasonal Nitrous Oxide and Methane Fluxes from Grain- and Forage-Based Production Systems in Wisconsin, USA

Agriculture in the midwestern United States is a major anthropogenic source of nitrous oxide (NO) and is both a source and sink for methane (CH), but the degree to which cropping systems differ in emissions of these gases is not well understood. Our objectives were to determine if fluxes of NO and CH varied among cropping systems and among crop phases within a cropping system. We compare NO and CH fluxes over the 2010 and 2011 growing seasons from the six cropping systems at the Wisconsin Integrated Cropping Systems Trial (WICST), a 20-yr-old cropping systems experiment. The study is composed of three grain and three forage cropping systems spanning a spectrum of crop diversity and perenniality that model a wide range of realistic cropping systems that differ in management, crop rotation, and fertilizer regimes. Among the grain systems, cumulative growing season NO emissions were greater for continuous corn ( L.) (3.7 kg NO-N ha) than corn-soybean [ (L.) Merr.] (2.0 kg NO-N ha) or organic corn-soybean-wheat ( L.) (1.7 kg NO-N ha). Among the forage systems, cumulative growing-season NO emissions were greater for organic corn-alfalfa ( L.)-alfalfa (2.9 kg NO-N ha) and conventional corn-alfalfa-alfalfa-alfalfa (2.5 kg NO-N ha), and lower for rotational pasture (1.9 kg NO-N ha). Application of mineral or organic N fertilizer was associated with elevated NO emissions. Yield-scaled emissions (kg NO-N Mg) did not differ by cropping system. Methane fluxes were highly variable and no effect of cropping system was observed. These results suggest that extended and diversified cropping systems could reduce area-scaled NO emissions from agriculture, but none of the systems studied significantly reduced yield-scaled NO emissions.

Browsing for conservation: springtime forage value of midstory shrubs of degraded oak savannas in southern Wisconsin.

Oak (Quercus spp.) savanna is a rare and dwindling ecosystem primarily due to the clearing of vast areas for agriculture and encroachment of woody midstory shrubs in the remnant areas. There is interest in introducing controlled grazing to re-open these ecologically sensitive semi-wooded areas. We report the forage quality and diet selection by Scottish Highland cattle (Bos taurus spp.), a breed recognized for their browsing behavior, of the most common shrubs in this ecosystem. Shrub species sampled included prickly ash (Xanthoxylem americana Mill), gooseberry (Ribes missouriense Nutt.), gray dogwood (Cornus racemesa L.), multiflora rose (Rosa multiflora Thunb. ex Murr.), black or red raspberry (Rubus spp.) and wild parsnip (Pastinaca sativa L). Leaf biomass was collected in June 2001 and 2002 and analyzed for forage quality. Animal observations showed that diet included a fairly even mixture of shrub leaves, grass and herbaceous forbs. Prickly ash and raspberry were most frequently browsed and had the highest crude protein (CP; 190 g kg - 1 ), while multiflora rose and gray dogwood, neither highly browsed upon, had the lowest levels of CP (120 g kg - 1 ). All shrubs had high in-vitro true digestibility, with prickly ash approaching 850 g kg - 1 (as compared to 688 g kg - 1 for mature alfalfa). The quality of the shrub layer in late spring is adequate to provide nutritional support for beef cattle as long as dry matter intake is not limited. Integrating shrubs into the rotation could expand the pasture base by providing feed at a time when cool-season pastures are typically quasi-dormant.

Improving fertilizer recommendations for subsistance farmers in West Africa: The use of agro-economic analysis of on-farm trials

A large number of zero, half and full rate fertilizer trials were conducted on-farm in Southern Senegal with rainfed lowland rice (n = 24), maize (n = 48), and groundnuts (n = 18). Trial sites were located according to farmer selected criteria: soil texture in the case of rice; compound garden versus outer field in the case of maize; and, previous cropping history in the case of groundnuts. Quadratic fertilizer response curves using all the cases explained only 16–29% of the variance. Subsequent stratification of the fields by soil organic matter, texture, and pH permitted the identification of fertilizer responsive and non-responsive fields. Response curves using only the tests conducted on soils without a limiting constraint explained 36 to 47% of the variance. At half rate fertilization levels VCRs of 3.8 (maize), 5.8 (rice) and 6.9 (groundnuts) resulted. Within productive fields, level of weed control, percent barrenness and final stand at harvest explained much of the remaining variation in yields for rice (82%), maize (61%) and groundnuts (76%) respectively. Response curves were then used in an economic analysis to address on-farm fertilizer allocation issues. Based on survey results and field trial data, partial budgets for small and medium-sized farms were developed. This analysis showed marginal rates of return of 400 and 165 percent to half and full rate fertilization, respectively. This type of fertilizer validation program, conducted on farmer-selected sites, improved targeting of recommendations, and helped to identify agronomic practices that should result in reduced economic risk and increased fertilizer adoption by farmers.

Buckwheat Species as Summer Cover Crops for Weed Suppression in No-Tillage Vegetable Cropping Systems

Abstract Buckwheat is a broadleaved annual species that is often used as a summer cover crop for its quick growth, weed suppressive ability, and ease of management. Tartary buckwheat is a species related to buckwheat, with many of the same traits valued in buckwheat as a cover crop. However, Tartary buckwheat has been reported to grow more vigorously than buckwheat, especially in cool conditions, which might fill a unique niche for vegetable farmers in Wisconsin and other northcentral states. Our research objectives were to determine the effectiveness of Tartary buckwheat relative to buckwheat for weed suppression, both during the cover-cropping phase and after cover-crop termination during cabbage production, and quantify weed suppression, soil compaction, soil nitrogen availability, and cabbage yield in no-tillage (roller-crimped or sickle-bar mowed) and conventional-tillage (rototilled) systems. Across three site-years, we found that buckwheat emerged earlier and produced 64% more shoot dry biomass than Tartary buckwheat. Pretermination weed shoot biomass (predominantly Amaranthus and Setaria spp.) in Tartary buckwheat treatments was approximately twice that of buckwheat, and did not differ from weed shoot biomass in a control fallow treatment. Cabbage yield did not differ between cover crop species nor did yield differ between conventional-tillage cover cropped and control fallow treatments. However, weed biomass was greater, and cabbage yield was reduced, in no-tillage compared to conventional-tillage treatments. We also found evidence of greater soil compaction and less nitrate–nitrogen (NO3–N) availability in no-tillage than conventional-tillage treatments. These results suggest that Tartary buckwheat is not a suitable summer cover crop alternative to buckwheat for weed suppression prior to cabbage production. Nomenclature: Cabbage, Brassica oleracea L. var. capitata; buckwheat, Fagopyrum esculentum Moench; Tartary buckwheat, Fagopyrum tataricum (L.) Gaertn.

An agro-economic analysis of field trials from a farming systems research perspective : weed control in rainfed lowland rice in Senegal

Using a farming systems approach, a multidisciplinary team in southern Senegal examined three strategies for weed control in rainfed lowland rice: use of herbicide; replacement of broadcast seeding by row seeding with mechanical seeders; and transplanting compared with direct seeding of rice. Thorough evaluation of the agronomic and economic benefits of these strategies for farmers was facilitated by supplementing the standard analysis of on-farm trials with multivariate analysis incorporating agronomic survey data to explain treatment effects better, and by considering technical and economic effects throughout the farming system. The agro-economic analysis led the team to conclude that: where soils are productive, herbicide use is a profitable investment; when converting to direct seeding, farmers should facilitate weeding by seeding in rows with a mechanical seeder; and transplanting should not be discouraged in areas where it is still feasible, since it is less time-consuming, fits in better with other farm activities and requires less fertilizer.

Social and environmental influences on tartary buckwheat (Fagopyrum tataricum Gaertn.) varietal diversity in Yunnan, China

Abstract Effective conservation strategies aimed to protect crop genetic resources require multiple sources of information. We used a combination of AFLP genotyping and farmer surveys to understand the extent, distribution and management of tartary buckwheat (Fagopyrum tataricum Gaertn.) diversity in its center of origin in Yunnan Province, China. We found genetic evidence of gene flow in tartary buckwheat throughout the study area, with small but statistically significant regional and village-level components. We also found genetic differentiation by seed color. Although most farmers reported exchanging seed in localized kinship networks, our results imply homogenizing gene flow is occurring. Yi ethnic farmers tend to plant more buckwheat than non-Yi farmers, and we found that in some communities, Yi farmers serve as seed sources for farmers of other ethnicities. Different tartary buckwheat varieties did not have different end uses; rather farmers maintained varietal diversity in order to protect crop yield and quality. Individual farmers’ seed exchange practices reflect their ideas about components of seed quality, as well as priorities in protecting buckwheat yield. From the standpoint of genetic resources conservation, the presence of a culturally rich farmer exchange network and hierarchical structuring of tartary buckwheat genetic diversity demonstrates the importance of maintaining an interlinked community of tartary buckwheat farmers in Yunnan.

A constant goal, changing tactics: The Krusenbaum dairy farm (1996–2005)

This case study documents the trajectory of a successful alternative dairy farm in southeastern Wisconsin. The 1990s were a difficult period for dairying and the Krusenbaum family entered this shifting field in 1990 with a 37-cow Holstein herd in a stanchion barn, 88 tillable hectares and a vision to gradually develop a biodynamic dairy. Low milk prices and the unrelenting workload associated with conventional dairying forced the family to look for alternative strategies. By 1995 they had converted all their land to 47 rotationally grazed paddocks, increased herd size to 70 cows and their annual net farm income had grown to a solid

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

54,000. The workload remained very heavy, and during the next few years they introduced a swing-16 milking parlor that approximately doubled their milking efficiency and allowed them to again increase herd size, implemented seasonal dairying and constructed an outwintering shed (1997) that greatly facilitated animal management during the winter. By 2002 the farming system had been, by and large, consolidated and by not focusing solely on milk production and crossbreeding with non-Holstein breeds, the herd benefited from improved reproductive vigor. They were then able to synchronize annual calving and the herds maximum nutritional needs with the spring flush of their pastures, which resulted in lowered purchased feed costs per cow. By this time, annual milk production was fairly constant [around 7400 kg rolling herd average (RHA)], herd health was good and annual net farm income had grown to