Intensive tillage degrades soil structure, decreases soil organic matter, and can cause soil compaction and erosion over time. Organic vegetable farmers are often dependent on tillage to incorporate crop residue, control weeds, and prepare seedbeds. Black, impermeable, polyethylene tarps applied on the soil surface and removed at planting can help suppress weeds before planting and reduce farmers’ reliance on tillage. However, little is known about how black tarps affect planting conditions and how they can be used to advance reduced tillage production systems. This study investigated the effects of tarp use and tarp duration on the soil environment, surface cover crop residue, and weed suppression to assess the efficacy of using tarps to improve reduced- and no-till practices for organic vegetable production. Experiments were conducted at three sites in the northeastern United States (Freeville, NY; Riverhead, NY; and Monmouth, ME) for 2 years. Following the termination of an oat cover crop, tarps were applied over untilled soils and left in place for four time periods: untarped (control), 3 to 5 weeks (short), 6 to 8 weeks (mid), and 10 or more weeks (long) before two removal dates. Soil moisture and temperature, cover crop residue, soil inorganic nitrogen, weed seed survival, and weed percent cover were measured after tarp removal. Soil moisture and temperature were generally higher under tarps at the time of removal compared with untarped areas at 10% to 55% and 1 to 3 °C, respectively, but the effects were inconsistent. Tarps significantly increased soil nitrate concentrations by 2-times to 21-times with longer tarp durations, resulting in higher concentrations compared with untarped controls. Tarps did not affect the amount of soil covered by cover crop residue and had no consistent effects on weed seed survival of Amaranthus powellii S. Wats. or Chenopodium album L., two common annual weed species in the Northeast. Tarping for at least 3 weeks reduced the weed percent cover by 95% to 100% at the time of removal. Increasing tarp duration beyond 3 weeks did not affect any measures except soil nitrate concentrations. These results indicate that tarps can facilitate the use of reduced-till and no-till practices for organic vegetables by creating a nutrient-rich and moist soil environment free of emerged weeds before planting without soil disturbance.

Close relationships among climatic factors and soil respiration (R s) are commonly reported. However, variation in R s across the landscape is compounded by site-specific differences that impede the development of spatially explicit models. Among factors that influence R s , the effect of ecosystem age is poorly documented. We hypothesized that R s increases with grassland age and tested this hypothesis in a chronosequence of tallgrass prairie reconstructions in central Iowa, U.S.A. We also assessed changes in root biomass, root ingrowth, aboveground net primary productivity (ANPP), and the strength of soil temperature and moisture in predicting R s. We found a significant increase in total growing season R s with prairie age (R 2 = 0.79), ranging from 714 g C m −2 in the youngest reconstruction (age 4) to 939 g C m −2 in the oldest prairie (age 12). Soil temperature was a strong predictor of intra-seasonal R s among prairies (R 2 = 0.78-0.87) but mean growing season soil temperature and moisture did not relate to total R s. The increase in R s with age was positively correlated with root biomass (r = 0.80) and ANPP (r = 0.87) but not with root ingrowth. Our findings suggest that growing season R s increases with tallgrass prairie age, root biomass, and ANPP during young grassland development.

Organic vegetable farmers rely on intensive tillage to control weeds, incorporate amendments and residues, and prepare seedbeds. Intensive tillage, however, can lead to a decrease in long-term soil health. Placing opaque plastic tarps on the soil surface weeks or months before planting can reduce weed pressure and may facilitate organic reduced tillage strategies, but few studies have documented tarp effects on crop productivity. The effect of tarp duration and tillage intensity on weeds and beet crop yields (cultivar Boro) was evaluated at three locations (Freeville, NY; Riverhead, NY; and Monmouth, ME), for two planting dates and over 2 years (2017 and 2018), resulting in a total of 10 experiments. Tarps were applied for three durations before projected planting dates: 1) 10+ weeks (long), 2) 6 to 8 weeks (mid), and 3) 3 to 5 weeks (short), then compared with an untarped control (none). Three levels of tillage intensity were applied after tarp removal: 1) 10 to 20 cm (conventional till), 2) 3 to 8 cm (reduced till), and 3) left undisturbed (no till), to understand interactions between tillage intensity and tarping. Tarp use of three or more weeks lowered weed biomass for several weeks after beet planting and at-harvest across most locations and years, but tarp duration beyond 3 weeks did not result in further reductions. Tarp use lowered at-harvest weed biomass and increased crop yield for reduced- and no-till systems with results similar to conventional-till. Tarping for 3 weeks could improve the viability of reduced- and no-till approaches for organic vegetable production.

Management constraints in reduced tillage organic vegetable production may be alleviated by combining strip tillage (ST) with overwintering cereal-legume cover crop mixtures. Field studies in Michigan and New York over 6 site-years evaluated the effects of preceding cover crops, including cereal rye (R; Secale cereale L.), hairy vetch (V; Vicia villosa Roth) and crimson clover (CC; Trifolium incarnatum), on N availability, weed management, and yields in ST organic cabbage (Brassica oleracea L. var. capitata). Cover crop treatments included R-legume mixtures (RV and RCC) planted under two spatial arrangements, standard full-width mixed [-M] vs. segregated strips [-S] (legumes planted in-row and R between-row), and R and V monocultures. Cover crop aboveground biomass (5-10 Mg ha -1 ) and N content (>90 kg N ha -1 ) were not different among RV and RCC but the C/N of RCC was 58% greater than RV. Cabbage yields after RCC-M were lower than RV-M in five of six cases with yield reductions ranging from 22 to 41%. Spatial arrangement had no effect on cabbage yield after RV but improved yields after RCC from 23 to 39% in one, relatively dry, site-year. Without N fertilizer, yields after RV and V were equivalent to or greater than R-S with 134 kg N ha -1 in seven of nine and four of four cases, respectively. Legume species and spatial arrangement had little or no impact on the efficacy of in-row mechanical cultivation, hand-weeding time or weed biomass.Overall, N supplied from V and RV mixtures was an important driver of ST organic cabbage yields across different soil types and weather conditions.

An understanding of changes in soil respiration (R s) and plant growth in tallgrass prairies planted into formerly cultivated land is critical if we are to predict the effects of grassland reconstructions on belowground carbon cycling. In addition, predicting changes in the ecosystem carbon balance in grassland reconstructions will require identifying the climatic and biological controls on R s across a landscape of cultivated and reconstructed grassland ecosystems. This study used a 12 yr chronosequence of tallgrass prairie reconstructions in central Iowa, including a no-till soybean field (age 0), to quantify the relationship between tallgrass prairie age, R s , root biomass, root ingrowth, and aboveground production. We also assessed the strength and interaction of soil temperature and soil moisture in predictions of R s across the chronosequence. Linear regressions showed a significant increase in standing root biomass carbon (R 2 = 0.89) and growing season R s (R 2 = 0.83) with prairie reconstruction age while changes in aboveground production and root ingrowth were less predictable. Growing season (gs) R s represented the largest carbon flux 1 Primary researcher and author 9 among prairie ages, ranging from 624 g C m-2 gs-1 in the soybean cropping system to 939 g C m-2 gs-1 in the oldest reconstruction (age 12), and was positively correlated with changes in root biomass. Among all tallgrass prairie reconstructions there was a strong, positive relationship between soil temperature and R s (R 2 = 0.80 to R 2 = 0.91) while the effect of soil moisture was greatest for the youngest prairie (age 4). Soil temperature was less correlated with R s in the no-till soybean field (R 2 = 0.40) and the inclusion of soil moisture added limited additional predictive power (R 2 = 0.48). Our findings indicate that an increase in cumulative R s with prairie reconstruction age was related to the interaction of soil temperature and the accumulation of root biomass with young grassland development.