No-till Soybean Research Articles

Initial nitrous oxide, carbon dioxide, and methane costs of converting conservation reserve program grassland to row crops under no‐till vs. conventional tillage

Around 4.4 million ha of land in USDA Conservation Reserve Program (CRP) contracts will expire between 2013 and 2018 and some will likely return to crop production. No-till (NT) management offers the potential to reduce the global warming costs of CO2, CH4, and N2O emissions during CRP conversion, but to date there have been no CRP conversion tillage comparisons. In 2009, we converted portions of three 9–21 ha CRP fields in Michigan to conventional tillage (CT) or NT soybean production and reserved a fourth field for reference. Both CO2 and N2O fluxes increased following herbicide application in all converted fields, but in the CT treatment substantial and immediate N2O and CO2 fluxes occurred after tillage. For the initial 201-day conversion period, average daily N2O fluxes (g N2O-N ha−1 d−1) were significantly different in the order: CT (47.5 ± 6.31, n = 6) ≫ NT (16.7 ± 2.45, n = 6) ≫ reference (2.51 ± 0.73, n = 4). Similarly, soil CO2 fluxes in CT were 1.2 times those in NT and 3.1 times those in the unconverted CRP reference field. All treatments were minor sinks for CH4 (−0.69 ± 0.42 to −1.86 ± 0.37 g CH4–C ha−1 d−1) with no significant differences among treatments. The positive global warming impact (GWI) of converted soybean fields under both CT (11.5 Mg CO2e ha−1) and NT (2.87 Mg CO2e ha−1) was in contrast to the negative GWI of the unconverted reference field (−3.5 Mg CO2e ha−1) with on-going greenhouse gas (GHG) mitigation. N2O contributed 39.3% and 55.0% of the GWI under CT and NT systems with the remainder contributed by CO2 (60.7% and 45.0%, respectively). Including foregone mitigation, we conclude that NT management can reduce GHG costs by ∼60% compared to CT during initial CRP conversion.

An economic risk analysis of no-till management for the rice-soybean rotation system used in Arkansas

Arkansas is the top domestic rice producer, representing nearly half of total US rice production. Sediment is one of the major pollutants in rice-producing areas of Arkansas. In order to mitigate this problem, no-till management is often recommended. No-till is not well understood by farmers who believe that no-till is less profitable due to lower yields offsetting cost savings. This study evaluates the profitability and net return variability of no-till in the typical rice (<i>Oryza sativa</i> L.)–soybean (<i>Glycine max</i> L.) rotation used in Arkansas rice production. Crop yields, crop prices, and prices for key production inputs (fuel and fertilizer) are simulated for the rotation, and net return distributions for rice, soybean, and the two-year rotation are evaluated for no-till and conventional till using stochastic efficiency with respect to a function (SERF) analysis. The results indicate that both risk neutral and risk-averse rice producers would prefer no-till over conventional till management in the two-year rice–soybean rotation and that no-till soybeans contribute greatly to the overall profitability of the rotation.

Overcoming Weed Management Challenges in Cover Crop–Based Organic Rotational No-Till Soybean Production in the Eastern United States

Cover crop–based organic rotational no-till soybean production has attracted attention from farmers, researchers, and other agricultural professionals because of the ability of this new system to enhance soil conservation, reduce labor requirements, and decrease diesel fuel use compared to traditional organic production. This system is based on the use of cereal rye cover crops that are mechanically terminated with a roller-crimper to create in situ mulch that suppresses weeds and promotes soybean growth. In this paper, we report experiments that were conducted over the past decade in the eastern region of the United States on cover crop–based organic rotational no-till soybean production, and we outline current management strategies and future research needs. Our research has focused on maximizing cereal rye spring ground cover and biomass because of the crucial role this cover crop plays in weed suppression. Soil fertility and cereal rye sowing and termination timing affect biomass production, and these factors can be manipulated to achieve levels greater than 8,000 kg ha−1, a threshold identified for consistent suppression of annual weeds. Manipulating cereal rye seeding rate and seeding method also influences ground cover and weed suppression. In general, weed suppression is species-specific, with early emerging summer annual weeds (e.g., common ragweed), high weed seed bank densities (e.g. &gt; 10,000 seeds m−2), and perennial weeds (e.g., yellow nutsedge) posing the greatest challenges. Due to the challenges with maximizing cereal rye weed suppression potential, we have also found high-residue cultivation to significantly improve weed control. In addition to cover crop and weed management, we have made progress with planting equipment and planting density for establishing soybean into a thick cover crop residue. Our current and future research will focus on integrated multitactic weed management, cultivar selection, insect pest suppression, and nitrogen management as part of a systems approach to advancing this new production system.

Sistemas de manejo do solo na recuperação de uma pastagem degradada em Rondônia

Na região amazônica, pastagens formadas e conduzidas de forma inadequada perdem a produtividade durante os primeiros anos em razão de superpastejo, ausência de adubação e de manutenção e emprego de espécies inadequadas para as condições edafoflorísticas da região. O objetivo deste estudo foi quantificar as modificações ocasionadas por diferentes sistemas de manejo nos atributos físicos de um Latossolo Vermelho-Amarelo (LVA), sob pastagem degradada no Estado de Rondônia, RO. Os sistemas de manejo utilizados nos tratamentos foram: T = testemunha; G = gradagem + NPK + micronutrientes; H = herbicida + NK + micronutrientes; A = plantio direto de arroz + NPK + micronutrientes; e S = plantio direto de soja + NPK + micronutrientes. O delineamento experimental foi em blocos ao acaso com quatro repetições. Para avaliar os tratamentos, amostras com estrutura indeformada foram coletadas em três profundidades (0-0,10; 0,10-0,20 e 0,20-0,30 m) para determinar a curva de retenção da água no solo, densidade do solo, resistência do solo à penetração de raízes, macroporosidade, microporosidade, porosidade total, estimativa do intervalo hídrico ótimo (IHO), densidade máxima do solo (Dsmax) e densidade relativa do solo (Dsrel). Os sistemas de manejo do solo adotados na recuperação da pastagem não proporcionaram melhorias significativas nos atributos físicos do solo, 40 meses após a implantação dos tratamentos. Em todos os sistemas de manejo, foram encontrados valores de densidade do solo acima do considerado ideal (1,40 Mg m-3) e abaixo do crítico (1,75 Mg m-3). Todos os sistemas de manejo apresentaram valores de densidade do solo relativa (Dsrel) acima do valor adotado como crítico (Dsrel = 86 %), exceto no sistema em que foi realizado o preparo do solo na profundidade de 0-0,10 m. A qualidade física do solo, avaliada pelo IHO, diminuiu com o aumento da profundidade do solo.

Qualidade física de Latossolos Amarelos sob plantio direto na região do Cerrado piauiense

O Cerrado vem sendo alvo de exploração sem a devida preocupação com a manutenção dos recursos naturais, e os sistemas de produção têm se caracterizado pelo uso intensivo do solo. O objetivo desta pesquisa foi avaliar o efeito do plantio direto na alteração das características físicas de Latossolos Amarelos cultivados com soja. A pesquisa foi realizada na Serra do Quilombo, localizada no cerrado piauiense. Foram verificadas as alterações nos atributos do solo em decorrência da utilização agrícola, que foi iniciada com plantio convencional (PC), posteriormente substituído pelo sistema de plantio direto (PD). Foram amostrados solos com diferentes históricos de uso: PC7/PD8: sete anos de plantio convencional e oito de plantio direto; PC5/PD4: cinco anos de plantio convencional e quatro de plantio direto; PC3/PD3: três anos de plantio convencional e três de plantio direto; e CN: solo com cerrado nativo. As propriedades avaliadas foram: distribuição das frações granulométricas, argila dispersa em água, grau de floculação, relação silte/argila, densidade do solo e das partículas, porosidade total, macro e microporosidade. Os resultados foram submetidos à análise de variância e, como análise complementar, utilizaram-se técnicas multivariadas. Para identificação das características físicas semelhantes do solo, utilizou-se a técnica de análise multivariada denominada análise fatorial. Maiores valores de densidade do solo e de microporosidade foram observados nos sistemas PD, e de macroporosidade e porosidade total, no CN. Os resultados mostraram que a implementação do sistema plantio direto alterou o volume total de poros e a macroporosidade, porém estes apresentaram valores dentro da faixa considerada não restritiva. A análise fatorial possibilitou a visualização conjunta dos atributos do solo, sendo as propriedades densidade do solo, porosidade total e macroporosidade as que mais sofreram variação nos sistemas de uso.

Variações nos teores do C total e isotópico do solo após substituição do Cerrado em sistemas agrícolas no Triângulo Mineiro

Os solos do Cerrado sofrem impactos resultantes da substituição da vegetação original em sistemas agrícolas traduzidos na forma de desequilíbrios nos estoques e natureza do carbono. A região do Triângulo Mineiro vem sendo intensamente desmatada por ser uma área pioneira de expansão do agronegócio e apresenta sérios problemas relacionados à erosão do solo. Esta pesquisa teve como objetivo avaliar as mudanças na quantidade (Ctotal) na natureza (δ13C) do carbono do solo após conversão do cerrado denso em áreas com diferentes usos agrícolas (pastagem, soja e rotação soja/milho), manejos (sistemas convencionais e plantio direto). Os resultados mostraram que as mudanças nos valores relacionados ao uso e manejo são determinados também pelas características texturais dos solos formados pela alteração de litotipos distintos. Dentre os diferentes usos e manejo, o maior enriquecimento da taxa de carbono foi determinado na área com soja/milho no sistema de plantio direto em solo argiloso e o maior empobrecimento em pastagens não manejadas em solos desenvolvidos da alteração do arenito das Formações Adamantina e Marília. Estes estudos são úteis para serem usados como indicadores de qualidade para a conservação ambiental.

Tillage and rotation effects on crop yield and profitability on a Black soil in northeast China

Fan, R., Zhang, X., Liang, A., Shi, X., Chen, X., Bao, K., Yang, X. and Jia, S. 2012. Tillage and rotation effects on crop yield and profitability on a Black soil in northeast China. Can. J. Soil Sci. 92: 463–470. To evaluate the feasibility of no-tillage (NT) practices for Black soils (Mollisols) in northeast China, knowledge of the effects of different tillage and rotation combinations on crop yield and profitability is required. An 8-yr field experiment was conducted to investigate variation of corn (Zea mays L.) and soybean (Glycine max L. Merr.) yields and economic returns under NT, moldboard plow (MP) and ridge tillage (RT) combined with continuous corn (C-C-C), corn-soybean (C-S), and corn-corn-soybean (C-C-S) rotations. Under C-S rotation, corn and soybean yields were similar to or slightly higher in NT than in MP and RT; NT corn profitability was 15.9% higher than MP, and NT soybean profitability was even higher, 62.9 and 22.4% higher than MP and RT, respectively. There were no differences in crop yield and profitability between the C-C-S and C-C-C rotations. The C-S under NT produced better yield and profitability, particularly in dry years, than the C-C-C and C-C-S rotations. Accordingly, NT combined with C-S would be a good practice to increase crop yields and profitability for the Black soils in northeast China.

Priming effects on soil organic carbon decomposition induced by high C:N crop inputs

Carbon budgets in soils can be computed by a simple equation in which inputs are accounted by the humification of residues added to the soil, and outputs are estimated by the respiration of soil organic carbon (CS). It is generally accepted that physical protection in soil aggregates and chemical recalcitrance limit the rate of CS decomposition. We propose that soybean-based crop sequences will have lower steady state CS stocks than those based on corn, because of lower C inputs and enhanced soil respiration of CS due the so-called priming effect. To address this hypothesis, we studied CS turnover from δ13C natural abundance changes in no-till corn and soybean crops. Soybean and corn crops were sown with a complete randomized design with three replicates on an old pasture with an intermediate soil δ 13C signal of -16.34. Soils were sampled at the beginning and after two years of continuous no till cropping. Aboveground and belowground C inputs were measured each year for corn and soybean crops. Soil and plant samples were analyzed for C, nitrogen and 13C/12C ratio. Corn C inputs where significantly higher than soybean (10.7 and 7.0 Mg ha-1), but no significant changes in CS where observed among treatments (68 Mg ha-1 in the fi rst 0.3 m). However, the Cs turnover and humification rates under corn (0.015 and 0.18 y-1) were higher than under soybean (0.006 and 0.11 y-1). Contrary to our predictions high C:N corn residues enhanced CS decomposition, but also the stabilization of fresh residues into CS, suggesting that soil microbes mine the soil organic matter while feeding on high C:N crop residues. Possible explanations for such result are discussed.

The Effect of Precipitation on Growth of No-tillage Soybean in the Upland Field Converted from Paddy Field

水田転換畑において，異なる降水条件下で生育した不耕起ダイズの乾物生産過程を耕起ダイズと比較することで，不耕起ダイズの生育特性を降水量の多少と関連付けて検討した．試験は播種から開花期までの降水量が大きく異なる 2009 年と 2010 年に行った．2009 年は，2010 年と比較して，播種から開花期までの降水の頻度が著しく高く総降水量も多かった．2009年は，耕起と比較して不耕起で，播種から開花期まで土壌水分含量が高く維持された．不耕起ダイズの主茎長，主茎節数，開花期以降の地上部乾物重は，2009 年には耕起ダイズと比較して抑制されていたが，2010 年は耕起ダイズと比較して旺盛であった．特に，地上部乾物重の増加が著しい開花期から着莢期の個体群成長速度 （CGR） および純同化率 （NAR） に，年次と耕起法間で有意な交互作用が認められた．その要因のひとつとして，2009 年は不耕起で土壌の過湿が著しかったため，耕起と比較して不耕起で，開花期の葉身窒素含有率が有意に低くなったことが考えられた．一方，2010 年では，開花期と着莢期の葉身窒素含有率および根粒の窒素固定活性は耕起法間で変わらず，CGR および NAR が耕起と比較して不耕起で有意に高かった理由は明らかではなかった．以上のことから，播種から開花期までの降水量が少ない年には，開花期以降の不耕起ダイズの生育は耕起と比較して旺盛となるが，播種から開花期までの降水量が多い年には，開花期以降の不耕起ダイズの生育は耕起と比較して抑制されることが示された．

Organic no-tillage system effects on soybean, corn and irrigated tomato production and economic performance in Iowa, USA

AbstractNovel technologies to reduce tillage in organic systems include a no-tillage roller/crimper for terminating cover crops prior to commercial crop planting. The objective of this experiment was to compare: (1) weed management and yield effects of organic tilled and no-tillage systems for corn (Zea maysL.), soybean [Glycine max(L.) Merr.] and irrigated tomato (Lycopersicon esculentumMill.), using a roller/crimper and two cover crop combinations [hairy vetch/rye (Vicia villosaRoth/Secale cerealeL.) and winter wheat/Austrian winter pea (Triticum vulgareL./Pisum sativumL. ssp.arvense(L.) Poir.)]; and (2) the economic performance of each system. Weed management ranged from fair to excellent in the organic no-tillage system for soybean and tomato crops, with the rye/hairy vetch mulch generally providing the most weed suppression. Corn suffered from low rainfall, competition from weeds and hairy vetch re-growth and, potentially, low soil nitrogen (N) from lack of supplemental fertilization and N immobilization during cover crop decomposition. No-tillage corn yields averaged 5618 and 634 kg ha−1in 2006 and 2007, respectively, which was 42–92% lower than tilled corn. No-tillage soybeans in 2007 averaged 2793 kg ha−1compared to 3170 kg ha−1for tilled soybeans, although no-tillage yields were 48% of tilled yields in the dry year of 2006. Irrigated tomato yields averaged 40 t ha−1in 2006 and 63 t ha−1in 2007, with no statistical differences among tillage treatments. Economic analysis for the three crops revealed additional cover crop seed and management costs in the no-tillage system. Average organic corn returns to management were US$1028 and US$2466 ha−1greater in the tilled system compared to the no-tillage system in 2006 and 2007, respectively, which resulted mainly from the dramatically lower no-tillage yields. No-tillage soybean returns to management were negative in 2006, averaging US$ −14 ha−1, compared to US$742 ha−1for tilled soybeans. However, in 2007, no-tillage soybean returns averaged US$1096 ha−1. The 2007 no-tillage irrigated tomato returns to management averaged US$53,515 compared to US$55,515 in the tilled system. Overall, the organic no-tillage soybean and irrigated tomato system demonstrated some promise for reducing tillage in organic systems, but until economic benefits from soil carbon enhancement can be included for no-tillage systems, soil improvements probably cannot offset the economic losses in no-tillage systems. Irrigation could improve the performance of the no-tillage system in dry years, especially if grain crops are rotated with a high-value irrigated tomato crop.

Desempenho agronômico de genótipos de capim-braquiária em sucessão à soja

O objetivo deste trabalho foi avaliar o desempenho agronômico de genótipos de capim-braquiária [Urochloa brizantha (Syn. Brachiaria brizantha)] em sucessão à soja, para uso em sistemas de integração lavoura-pecuária. Os genótipos Marandu, MG 4, Xaraés, Piatã, Arapoty e B 6, foram avaliados na safrinha, durante a estação seca, e a soja na safra de verão, em esquema de sucessão, de 2007 a 2010. Em cada ano, as forrageiras foram semeadas em março, avaliadas em cortes sucessivos até o final de setembro e dessecadas em outubro para a realização do plantio direto da soja em novembro. Utilizou-se o delineamento de blocos ao acaso, com quatro repetições. Xaraés e B 6 estiveram entre os genótipos com maior produção de forragem. A cultivar Xaraés apresentou menores teores de proteína bruta, digestibilidade in vitro da matéria orgânica, cálcio e fósforo, embora esses teores possam ser considerados bons para o gênero, uma vez que o solo de cultivo apresentava boa fertilidade. Há variação entre os genótipos de U. brizantha quanto ao desempenho na safrinha. A cultivar Xaraés e o genótipo B 6 destacam-se para compor sistemas de produção integrados com lavoura. Os genótipos MG 4 e B6 são facilmente dessecados com o herbicida glifosato. A produtividade de grãos de soja não é significativamente afetada pelo cultivo em sucessão aos genótipos de U. brizantha.

Carbon debt of Conservation Reserve Program (CRP) grasslands converted to bioenergy production

Over 13 million ha of former cropland are enrolled in the US Conservation Reserve Program (CRP), providing well-recognized biodiversity, water quality, and carbon (C) sequestration benefits that could be lost on conversion back to agricultural production. Here we provide measurements of the greenhouse gas consequences of converting CRP land to continuous corn, corn-soybean, or perennial grass for biofuel production. No-till soybeans preceded the annual crops and created an initial carbon debt of 10.6 Mg CO(2) equivalents (CO(2)e)·ha(-1) that included agronomic inputs, changes in C stocks, altered N(2)O and CH(4) fluxes, and foregone C sequestration less a fossil fuel offset credit. Total debt, which includes future debt created by additional changes in soil C stocks and the loss of substantial future soil C sequestration, can be constrained to 68 Mg CO(2)e·ha(-1) if subsequent crops are under permanent no-till management. If tilled, however, total debt triples to 222 Mg CO(2)e·ha(-1) on account of further soil C loss. Projected C debt repayment periods under no-till management range from 29 to 40 y for corn-soybean and continuous corn, respectively. Under conventional tillage repayment periods are three times longer, from 89 to 123 y, respectively. Alternatively, the direct use of existing CRP grasslands for cellulosic feedstock production would avoid C debt entirely and provide modest climate change mitigation immediately. Incentives for permanent no till and especially permission to harvest CRP biomass for cellulosic biofuel would help to blunt the climate impact of future CRP conversion.

Organically Managed No‐Tillage Rye–Soybean Systems: Agronomic, Economic, and Environmental Assessment

A major challenge that organic grain crop growers face is weed management. The use of a rye (Secale cereale L.) cover crop to facilitate no‐tillage (NT) organic soybean [Glycine max (L.) Merr.] production may improve weed suppression and increase profitability. We conducted research in 2008 and 2009 to determine the effect of rye management (tilling, crimping, and mowing), soybean planting date (mid‐May or early June), and soybean row width (76 or 19 cm), on soybean establishment, soil moisture, weed suppression, soybean yield, and profitability. Soybean establishment did not differ between tilled and NT treatments; and soil moisture measurements showed minimal risk of a drier soil profile in NT rye treatments. Rye mulch treatments effectively suppressed weeds, with 75% less weed biomass than in the tilled treatment by mid‐July. However, by this time, NT soybean competed with rye regrowth, were deficient in Cu, and accumulated 22% as much dry matter (DM) and 28% as much N compared to the tilled treatment. Soybean row width and planting date within NT treatments impacted soybean productivity but not profitability, with few differences between mowed and crimped rye. Soybean yield was 24% less in the NT treatments than the tilled treatment, and profitability per hectare was 27% less. However, with fewer labor inputs, profitability per hour in NT rye treatments was 25% greater than in tilled soybean; in addition, predicted soil erosion was nearly 90% less. Although soybean yields were less in NT rye mulch systems, they represent economically viable alternatives for organic producers in the Upper Midwest.

Rolled Rye Mulch for Weed Suppression in Organic No-Tillage Soybeans

Rising demand for organic soybeans and high price premiums for organic products have stimulated producer interest in organic soybean production. However, organic soybean producers and those making the transition to organic production cite weed management as their main limitation. Current weed management practices heavily rely on cultivation. Repeated cultivation is expensive and has negative consequences on soil health. Research is needed to improve organic reduced tillage production. Rye cover crop mulches were evaluated for weed suppression abilities and effects on soybean yield. Experiments were planted in 2008 and 2009 at three sites. Rye was planted in the fall of each year and killed at soybean planting with a roller/crimper or flail mower, creating a thick weed-suppressing mulch with potential allelopathic properties. The mulch was augmented with one of three additional weed control tactics: preemergence (PRE) corn gluten meal (CGM), postemergence (POST) clove oil, or postemergence high-residue cultivation. Roll-crimped and flail-mowed treatments had similar weed suppression abilities at most sites. There were no differences between CGM, clove oil, or cultivation at most sites. Sites with rye biomass above 9,000 kg ha−1of dry matter provided weed control that precluded soybean yield loss from competition. In Goldsboro 2008, where rye biomass was 10,854 kg ha−1of dry matter, the soybean yield in the rolled rye treatment was not significantly different from the weed-free treatment, yielding at 2,190 and 2,143 kg ha−1, respectively. Likewise, no difference in soybean yield was found in Plymouth 2008 with a rye biomass of 9,256 kg ha−1and yields of 2,694 kg ha−1and 2,809 kg ha−1in the rolled rye and weed-free treatments, respectively. At low rye biomass levels (4,450 to 6,606 kg ha−1), the rolled rye treatment soybean yield was 628 to 822 kg ha−1less than the weed-free treatment. High rye biomass levels are critical to the success of this production system. However, high rye biomass was, in some cases, also correlated with soybean lodging severe enough to cause concern with this system.

Radiological impact of phosphogypsum surface application in a no-till system in Southern Brazil

The objective of this work was to determine the impact of phosphogypsum application on 226Ra and 228Ra activities in the soil and on their accumulation in soybean grains. A field experiment was carried out in Paraná state, Brazil, on a loamy Typic Hapludox, under no-till system, with increasing phosphogypsum rates: 4, 8, and 12 Mg ha-1. GammA ray spectrometry was carried out using HPGe detectors with 45 and 10% relative efficiencies, for soybean grains and soil, respectively. No increment of 226Ra and 228Ra activities was observed due to the increase in phosphogypsum rates in the soil, and a small reduction was noticed in the grains. Average values found for 226Ra and 228Ra activities were 37 and 57 Bq kg-1 in the soil and 1.44 and 3.19 Bq kg-1 in soybean grains. The application of phosphogypsum for no-till soybean production is a safe practice regarding the risks of radiation damage to human health

Water and energy footprints of bioenergy crop production on marginal lands

Water and energy demands associated with bioenergy crop production on marginal lands are inextricably linked with land quality and land use history. To illustrate the effect of land marginality on bioenergy crop yield and associated water and energy footprints, we analyzed seven large-scale sites (9–21 ha) converted from either Conservation Reserve Program (CRP) or conventional agricultural land use to no-till soybean for biofuel production. Unmanaged CRP grassland at the same location was used as a reference site. Sites were rated using a land marginality index (LMI) based on land capability classes, slope, soil erodibility, soil hydraulic conductivity, and soil tolerance factors extracted from a soil survey (SSURGO) database. Principal components analysis was used to develop a soil quality index (SQI) for the study sites based on 12 soil physical and chemical properties. The water and energy footprints on these sites were estimated using eddy-covariance flux techniques. Aboveground net primary productivity was inversely related to LMI and positively related to SQI. Water and energy footprints increased with LMI and decreased with SQI. The water footprints for grain, biomass and energy production were higher on lands converted from agricultural land use compared with those converted from the CRP land. The sites which were previously in the CRP had higher SQI than those under agricultural land use, showing that land management affects water footprints through soil quality effects. The analysis of biophysical characteristics of the sites in relation to water and energy use suggests that crops and management systems similar to CRP grasslands may provide a potential strategy to grow biofuels that would minimize environmental degradation while improving the productivity of marginal lands.

Recovery of degraded pasture in Rondônia: macronutrients and productivity of brachiaria brizantha

Pasture is the main form of land use in Amazonia. Over time the pasture grass loses vigor and yields decrease, indicating a certain degree of degeneration. The main causes of degradation are lack of pasture maintenance and subsequent weed infestation, the choice of regionally unsuitable forage species and excessive grazing. The main purpose of this study was to evaluate the impact of different recovery managements on soil chemical properties and grass yield of a degraded pasture in Rondônia. For this purpose, an experiment was installed in October 2001, consisting of five treatments: C = control; HA = harrowing + NPK + micronutrients; HE = Herbicide + NK + micronutrients; R = No-tillage rice + NPK + micronutrients; and S = No-tillage soybean + PK + micronutrients. The following N, P and K sources were used: ammonium sulfate for N, calcined phosphate for P and potassium chloride for K. The experiment was arranged in a randomized block design with four replications. The shoot dry matter yield of the grass was analyzed as of the 35th month of experimentation, in a dry and a rainy period. Phosphorus fertilization resulted in significant increases in Ca2+ and Mg2+ and increasing trend of P in the topsoil in the initial months of the experiment in treatments HA and S and increases in Ca2+ and P (trend) in the treatment R. The cumulative production of Brachiaria brizantha, from Sep/2004 to Mar/2005, was 30,025, 28,267 and 27,735 kg ha-1 shoot dry matter in the treatments HA, R and S, respectively. These values differed significantly from treatments C and HE, with 17,040 and 17,057 kg ha-1, respectively. It was concluded that phosphorus fertilization associated to pasture reform was effective to raise the dry matter yield of Brachiaria brizantha. Rice or soybean under no-tillage is recommended as a practice of pasture recovery, due to the residual effect of fertilization.

Use of a Rolled-rye Cover Crop for Weed Suppression in No-Till Soybeans

Cover crop management with a roller/crimper might reduce the need for herbicide. Weed suppression from a rolled cereal rye cover crop was compared to no cover crop with and without postemergence herbicide application in no-till soybean. The experiment was designed as a two-way factorial with rye termination and soybean planting date as the first factor and weed control treatment as the second. Cereal rye was drill-seeded in late September and managed using glyphosate followed by a roller/crimper in the spring. Soybean was no-till seeded after rolling and glyphosate was applied postemergence about 6 wk after planting to half the plots. Rye biomass doubled when delaying rye kill by 10 to 20 d. Weed density and biomass were reduced by the rye cover crop in all site–location combinations except one, but delaying rye kill and soybean planting date only reduced both weed density and biomass at a single location. The cover crop mulch provided weed control similar to the postemergence herbicide in two of four locations. Treatments did not affect soybean grain yield in 2007. In 2008, yield at Landisville with rye alone was equal to those yields receiving the postemergence herbicide, whereas at Rock Springs, it was equivalent or less. The net added cost of a rye cover crop was $123 ha−1with or $68.50 ha−1without a postemergence herbicide application. A rolled-rye cover crop sometimes provided acceptable weed control, but weed control alone did not justify the use of the cover crop. The potential for reduced herbicide use and other ecosystem services provided by a cover crop justify further refinement and research in this area.

Cover-Crop Roller–Crimper Contributes to Weed Management in No-Till Soybean

Termination of cover crops prior to no-till planting of soybean is typically accomplished with burndown herbicides. Recent advances in cover-crop roller–crimper design offer the possibility of reliable physical termination of cover crops without tillage. A field study within a no-till soybean production system was conducted in Urbana, IL, from 2004 through 2007 to quantify the effects of cover crop (cereal rye, hairy vetch, or bare soil control), termination method (chemical burndown or roller–crimper), and postemergence glyphosate application rate (0, 1.1, or 2.2 kg ae ha−1) on soybean yield components, weed–crop interference, and soil environmental variables. Biomass of weeds surviving management within a soybean crop following either a vetch or rye cover crop was reduced by 26 and 56%, respectively, in the rolled system compared to the burndown system. Soybean yield loss due to weed interference was unaffected by cover-crop termination method in soybean following a rye cover crop, but was higher in the rolled than burndown treatment in both hairy vetch and bare soil treatments. In soybean following a rye cover crop, regardless of termination method, yield loss to weed interference was unaffected by glyphosate rate, whereas in soybean following a vetch cover crop or bare soil, yield loss decreased with glyphosate rate. Variation in soybean yield among cover crops and cover-crop termination treatments was due largely to differences in soybean establishment, rather than differences in the soil environment. Use of a roller–crimper to terminate a cover crop preceding no-till soybean has the potential to achieve similar yields to those obtained in a chemically terminated cover crop while reducing residual weed biomass.

Elevated carbon dioxide alters chemical management of Canada thistle in no-till soybean

Differential responses of crops and weeds to anthropogenic climatic change may alter competition and crop yields. Here we examine the role of current and projected increases in carbon dioxide concentration [CO 2], on soybean growth and seed yield with and without competition from Canada thistle ( Cirsium arvense, a common perennial weed in soybean farming systems), over a 3-year period using no-tillage (i.e., no physical cultivation for weed removal) practices. Weed control was implemented by applying herbicide (glyphosate) as a pre-emergent treatment at the beginning of each growing season. Under a weed-free condition, round-up ready soybean demonstrated a significant response of seed yield and total above-ground biomass to elevated [CO 2], but no synergistic effect of no-till over time on the response of biomass or yield to [CO 2] was observed. Average above-ground weight of Canada thistle was significantly greater at elevated [CO 2] for 2008 and 2009, and establishment of thistle increased as a function of [CO 2] over time even with pre-emergent applications of glyphosate. Although the presence of Canada thistle reduced seed yield and biomass of soybean for both CO 2 treatments from 2007 to 2009, the reduction was higher for the elevated [CO 2] treatment, and a significant [CO 2] × Canada thistle interaction was observed for these parameters. Overall, these are the first data to indicate that perennial weeds associated with no-tillage practices could be a greater impediment to crop yields and harder to control chemically in response to rising levels of atmospheric carbon dioxide.