Innovative method for cover crop termination using engine exhaust heat

Abstract. Sustainable no-till practices utilize cover crops to protect the soil surface and to improve soil properties. Proper cover crop management is the key for successful planting of the main crop directly into cover crop residue without interfering with planting operations. In the Southern United States, the recommended time to plant cash crops into desiccated residue cover is typically three weeks after cover crop termination when the termination rate exceeds 90%; this minimizes nutrient competition between cover and cash crops. The standard method to manage cover crops is mechanical termination utilizing rollers/crimpers. This technique flattens and crimp plants to expedite termination. Another method that has been used in agriculture is to injure (desiccate) plants utilizing an external heat source. An example of utilizing an external heat source has been used in vegetable production for weed control. However, there is a need to evaluate another heat source such as exhaust heat generated by internal combustion engines (which otherwise is completely wasted) for cover crop termination effectiveness. To achieve cover crop termination with exhaust heat, a prototype was invented on board a walk-behind tractor powered by a single cylinder gasoline engine from which exhaust heat was funneled from the exhaust manifold to a perforated steel rectangular tube maintaining 204°C against a flattened cover crop to damage plant tissue. The heat pusher was equipped with electric heater strips to provide supplemental heating. Three electric heater strips (front, middle, back relative to the direction of travel) were supplied with electrical energy by a generator powered by the tractor’s PTO and generated temperatures of 379°C to 421°C with a temperature transfer efficiency of 83% to 91%. The performance of the unit with and without supplemental heating was compared with standard mechanical roller/crimper. Results demonstrated that using the exhaust heat concept can be a viable option to terminate cover crops. The exhaust heat transferring channel could be better insulated to exceed the lower 23% temperature transfer efficiency achieved by the device. Cover crop termination data during three weeks of evaluation indicated that the heat-based system was as effective as a mechanical roller/crimper. Keywords: Cereal rye, Cover crop termination, Crimson clover, Exhaust heat, Flattening cover crops, Heat transfer, Heater, Plant termination.

Introduction: According to the importance of corn in supplying the human food directly and indirectly, it is one of the most important plants among crops. One of the major problems in corn production systems, is competition with weeds that reduce corn yield significantly. Weeds not only reduce crop yields but also decrease the commercial quality and the feeding palatability of main crops. They enhance the soil seed bank of weeds, which may cause continuous weed infestation of field crops as well. Herbicide application is a reliable and highly effective method for weed control. However, demand for safe food products that have been produced with a minimum application of chemical inputs is increasing. Therefore, farmers interested in weed management have to rely on other control approaches. An alternative weed control method is the use of cover crops, which can suppress the growth of weeds by preventing them from light and by producing allelopathic compounds. Cover crops successfully have been integrated into conservational agriculture systems in many areas of the world. Legumes are used as cover crop because of their rapid growth, in addition their potential to provide further nitrogen,along with high ability to compete with weeds. Materials and Methods: In order to study the effect of cover crops (soybean and wheat) and different fertilizers sources on yield of corn and weed control, a filed experiment was conducted in randomized complete block design with three replications in 2012. Treatments included two cover crop (wheat and soybean) and three fertilizer (no fertilizer, chemical fertilizer and compost)..Fertilizer treatments was used according to soil analysis and requirement of corn (as a main plant). Weed-infestation and weed-free plots were used as controls. Study cultivars of corn, wheat and soybean were NS-640, Milan and Sari, respectively. Planting of corn was in June and cover crop was planted with corn simultaneously and between corn rows. The dominant weed species were velvetleaf (Abutilon theophrasti Medic.), johnson grass (Sorghum halepense (L.) Pers.), wild melon (Cucumis melo var. agrestis) and giant foxtail (Setaria glauca L.) in the field. In order to determine the dry weight and density of weeds, three-stage sampling was performed from the middle rows of corn. Corn yield was also measured by mechanical harvesting in middle rows and adjusting to 14% moisture. A week before the final harvest, ten plants of corn were selected randomly from the three middle rows of each plot and yield components including the number of rows in corn, number of kernels per row, weight of 1000 grains was measured. Results and Discussion: The results showed that soybean cover crop reduced weed density compared to control in weed infestated plots, but wheat was not successful in suppressing weeds and reducing their density due to poor biomass and dying at the end of growing season . So, the lowest dry matter of velvetleaf, wild melon and other weeds were related to planted corn with soybean and compost and the maximum was related to monoculture of corn with weed infestation. Results of analysis of variance indicated treatments had significant effect on grain yield. The lowest yield of corn (2733.3 Kg ha-1) was in weed-infestation control while the highest one (12124.0 and 8351.3 Kg ha-1 respectively) was in weed-free control and soybean’ cover crop plus compost. For both cover crops between fertilizer treatments, compost and chemical fertilizer had more corn biological yield than no fertilizer and differences between this two fertilizer treatments wasn’t significant. Reduction of yield under no fertilizer treatments was due to competition for nutrients, light between weed and corn. The maximum and minimum number of rows in corn and number of kernels per row respectively was obtained with monoculture of corn in weed free and weed infestation, while the maximum weight of 1000 grains was observed in soybean with applying compost. Generally, the living mulch as cover crops can reduce competition between weeds and the main crop. Conclusion: As cover crops reduce weeds growth, and there was no significant difference between chemical and organic fertilizer in corn yield, so we can use these two options for producing optimum yield in sustainable agriculture. Results showed application of soybean as cover crop, especially integrated with organic fertilizers, can be an alternative approach for herbicides and are more effective than the others.

Cover cropping, the practice of planting a non-commodity crop between rotations of commodity crops, is an emerging conservation practice in row-crop agriculture. Cover crops are used to improve soil health and reduce the need for chemical inputs. Cover crops also provide habitat for wildlife in fields that typically are not utilized by most wild occupants of highly fragmented agroecosystems. Though increasing wildlife habitat generally is viewed as a benefit, presence of some species may conflict with economic goals of producers. Voles (Microtus), a genus of rodent typically found in grassland habitats, have been reported by producers to consume the commodity soybean (Glycine max) crop, however, few evidence-based strategies exist to prevent vole use of fields and subsequent damage. I examined how voles perceive cover crops as a source of habitat and how fields may be monitored and manipulated to prevent damage by voles. I conducted captive feeding trials to identify common cover crops selected as forage by 10 meadow (M. pennsylvanicus) and 15 prairie voles (M. ochrogaster). I also gathered data on landscape features, weather conditions, and farming techniques for 66 cover-cropped fields and identified factors most important to predicting vole damage to soybeans. Lastly, I surveyed 38 cover-cropped fields for vole sign and explored other covariates, including cover-crop density, that contributed to vole damage to young soybean plants. Both meadow and prairie voles commonly preferred clover (Trifolium), alfalfa (Medicago sativa), and hairy vetch (Vicia villosa) cover crops as forage, whereas canola (Brassica napus) was avoided by both vole species. Cover crops that were highly (or minimally) preferred were selected (avoided) more consistently than plants that were moderately preferred. Selection of cover crops by voles was affected by diversity of available forage, nutritional characteristics of the plants, and individual vole personalities. Probability of vole damage to cover-cropped fields was most strongly tied to soil type, days of snow, and permanent grassland habitat available. Fields that had been cover cropped for >3 years, had not been tilled, contained high proportions of well-drained soils, and 5-7% grassland habitat within 50 m were at greater risk for vole damage, especially if winter snow cover was minimal. Increased levels of vole damage also were found in fields containing a greater number of vole burrows and denser plant cover during spring surveys. Farmers may survey fields for vole sign and evaluate field attributes and weather conditions to identify where and when vole damage is likely to be greatest. They may reduce in-field vegetative cover, expand permanent grassland habitat at field edges to cover >7% of land area within 50 m of the field, plant cover crops that do not provide ideal forage, or apply conservation tillage to reduce habitat suitability of cover-cropped fields for voles before planting the commodity soybean crop.

به منظور بررسی اثرات زمان‌های کاشت بهاره، تابستانه و پاییزه و نیز مدیریت آبیاری و استفاده از گیاهان پوششی، بر ویژگی‌های رشد و عملکرد گیاه دارویی زعفران (Crocus sativus L.) آزمایشی در مزرعه تحقیقاتی دانشکده کشاورزی دانشگاه فردوسی مشهد در سال‌های زراعی 89-1388 و 90-1389، به صورت کرت‌های دوبار خرد شده در قالب طرح پایه بلوک‌های کامل تصادفی با سه تکرار اجرا شد. فاکتورهای آزمایشی عبارت بودند از: تاریخ کاشت بهاره، تابستانه و پاییزه زعفران به عنوان فاکتور اصلی (اول خرداد ماه، اول مرداد ماه و اول مهر ماه)، مدیریت آبیاری به عنوان فاکتور فرعی (انجام آبیاری و عدم انجام آبیاری پس از هر تاریخ کاشت) و کاربرد گیاهان همراه در سال دوم آزمایش به عنوان فاکتور فرعی فرعی [شبدر ایرانی (Trifolium resopinatum L.)، خلر (Lathyrus sativus L.) و شاهد]. نتایج نشان داد که با تأخیر در کاشت بنه‌ها از اول خرداد به اول مهر، شاخص‌های کمی زعفران به طور قابل ملاحظه‌ای کاهش پیدا کرد و شدت کاهش در سال دوم آزمایش به مراتب بیشتر بود. بیشترین عملکرد گل در تاریخ کاشت مرداد ماه (به ترتیب 28 و 98 کیلوگرم در هکتار برای سال‌های اول و دوم آزمایش) و کمترین آن در تاریخ کاشت مهر ماه (به ترتیب 18 و 34 کیلوگرم در هکتار برای سال‌های اول و دوم آزمایش) به دست آمد. کاشت زعفران در تاریخ اول مرداد ماه موجب بهبود سرعت گل‌دهی و کاهش نسبی سرعت ظهور برگ گردید. عدم آبیاری پس از کاشت باعث افزایش شاخص‌های کمی زعفران شد؛ به طوری‌که عملکرد گل در تیمار انجام آبیاری پس از کاشت در سال اول نه و در سال دوم 43 کیلوگرم در هکتار و برای تیمار عدم انجام آبیاری در سال‌های اول و دوم به ترتیب 37 و 78 کیلوگرم در هکتار بود. بیشترین تعداد گل در هکتار (480000 گل در هکتار) و نیز بیشترین درصد بنه‌های گل‌دهنده (100 درصد) در سال دوم آزمایش و در تیمار تاریخ کاشت خرداد ماه و عدم انجام آبیاری پس از کاشت به دست آمد. کاربرد گیاهان پوششی به خصوص خلر تا حدودی باعث بهبود ویژگی‌های رشد و عملکرد زعفران گردید؛ به طوری‌که استفاده از این گیاه پوششی، عملکرد گل و کلاله را در مقایسه با شاهد حدود دو درصد افزایش داد. همچنین بیشترین سرعت گل‌دهی و کمترین سرعت ظهور برگ در تیمارهای تاریخ کاشت خرداد ماه، عدم انجام آبیاری پس از کاشت و کاربرد گیاه پوششی خلر مشاهده شد.

Plant microbiomes are increasingly recognized for their potential to help plants with critical functions such as nutrient acquisition. Nitrogen is the most limiting nutrient in agriculture and growers apply substantial amounts to meet crop needs. Only 50% of N fertilizers are generally taken up by plants and the rest is subject to loss which negatively affects environmental quality. Organic fertilizers such as cover crops and animal manure can help reduce this loss, though these materials must mineralize via microbial mediated processes before they are available for plant uptake, which makes managing fertility using these sources difficult. Some plants can scavenge nutrients from organic materials by stimulating positive priming processes in soil. Carrot (<i>Daucus carota.</i> L) is known as an N scavenging crop, making it an ideal model crop to study these interactions. In a greenhouse trial, soils were amended with an isotopically labeled corn residue to track N movement, and planted with one of five carrot genotypes expected to differ in nitrogen use efficiency (NUE). Changes in soil b-glucosidase activity, ammonium (NH₄⁺-N) and nitrate (NO₃^--N) concentrations, soil bacterial community composition, weight and carbon and N concentrations, and total δ¹⁵N of above and below ground carrot biomass were determined. Results indicate that there are genetic differences in the ability of carrots to promote priming under N limited conditions, which could be exploited to enhance NUE in carrots. Soil microbial communities differed between genotypes, indicating that some of these microbes could play a role in the differential N scavenging responses observed, and/or contribute to other important functions such as resistance to pests. Endophytic microbes residing inside carrot taproots also have potential to contribute to NUE and other benefits, but are notoriously difficult to isolate and culture. New next generation sequencing technologies have revolutionized the study of microbiomes, though using these tools to study bacterial endophytes in plants is still difficult due to co-amplification of plant organelles. Consequently, a second study was conducted to determine if subjecting carrot tissues to hollow fiber microfiltration followed by enzymatic digestion could enhance recovery and amplification of bacterial endophytes. Carrot taproot digests were subject to amplification using a standard V3-V4 16S primer set, as well as two alternative (blocking and mismatch) primer sets that have prevented amplification of plastids/mitochondria in other plant species. Results indicate that the microfiltration/digestion procedure can increase the number of bacterial endophyte OTUs assigned and could be further optimized for use in carrots. The blocking and mismatch primer sets were not as effective in blocking co-amplification of plant products as they are in other studies, possibly due to the presence of a high number of chromoplasts in carrot tissues. Taxonomic assignment of bacterial endophytes differed significantly between the primer sets, indicating that multiple primer sets may be needed to fully characterize these communities in carrots. The enzymatic digestion procedure could artificially inflate certain taxa, which could be helpful if targeting specific taxa. These studies demonstrate that carrots are intimately connected with microbes residing in the soil and within their taproots, and further exploration of these plant-soil-microbial relationships could enhance the yield and sustainability of carrot production systems.

Investigation on the hydrogen production by methanol steam reforming with engine exhaust heat recovery strategy

In recent years, increasing application of chemical herbicides has raised concerns over their destructive impacts on living organisms and environmental health and it requires studies on non-chemical weed management methods. As a result, this experiment was initiated in November 2008 at experimental field of Islamic Azad University, Karaj Branch, in order to evaluate weed-suppressive ability of winter rye cover crop and mulch, and its effects on following corn yield production. Treatments included three rye seeding rates (500, 750 and 1000 kernels/m2) and three rye kill dates (29/3/2009, 15/4/2009 and 3/5/2009). In the fall 2008 rye was planted, then in the above three dates have been killed and left on the soil surface to provide mulching effect. Then in middle of June 2009, corn plants planted on the same plots of winter rye. Weeds density and biomass production were monitored in the fourth, sixth and eighth weeks after planting (WAP) corn. Corn yield production was also measured in late October 2009. Results showed that rye seeding rate has not affected weeds significantly but rye kill date had significant effect. The first kill date stimulated weeds germination and growth. The third kill date reduced density of all weeds in the fourth WAP on average 28.73% and their biomass production in the sixth WAP on average 21.38%. This treatment also increased corn grain production 7.89% at the end of the season. Finally, results of the experiment indicate that using cover crops should be combined with other methods to control weeds efficiently and to prevent yield production loss.

به‌منظور بررسی اثر تاریخ کاشت و تغذیه فسفر بر رشد و عملکرد باقلا آزمایشی در سال زراعی 93- 1392 در مزرعه پژوهشی دانشگاه کشاورزی و منابع طبیعی رامین خوزستان اجرا گردید. آزمایش به‌صورت کرت‏های خرد‌شده در قالب طرح بلوک‌های کامل تصادفی با چهار‌تکرار انجام شد. فاکتورهای آزمایش شامل پنج‌تاریخ کاشت 10‌مهر، 25‌مهر، 10‌آبان، 25‌آبان و10‌آذر در کرت‏های اصلی و کود اکسید‌فسفر (P2O5) به‌میزان صفر، 50، 100 و 150‌کیلوگرم در هکتار از منبع سوپر‌فسفات‌تریپل در کرت فرعی در‌نظر گرفته شد. نتایج آزمایش نشان‌داد که اثر تاریخ کاشت و کود فسفر و اثر متقابل آنها بر صفت‏های ارتفاع بوته، ارتفاع اولین غلاف از سطح زمین، شاخص سطح برگ، تعداد شاخه فرعی، تعداد غلاف در بوته، تعداد دانه در غلاف معنی‏دار بود. مقایسه میانگین‏ها نشان‌داد که تاریخ کاشت اثر معنی‏داری بر عملکرد دانه داشت، به‌طوری‌که بیشترین عملکرد دانه مربوط به تاریخ کاشت ‌10آبان (میانگین تولید 2702کیلوگرم در هکتار) و کمترین عملکردها مربوط به تاریخ‏های کاشت 10آذر (با میانگین تولید 1903کیلوگرم در هکتار) و 10مهر (با میانگین تولید 1943کیلوگرم در هکتار) بود. در این آزمایش استفاده از فسفر بالاتر از 100کیلوگرم در هکتار اثر معنی‏داری بر روی عملکرد نداشت. تأخیر در کاشت باقلا باعث کاهش عملکرد آن شد، اما از طریق تغذیه فسفر می‏توان این کاهش عملکرد را تا حدودی جبران نمود؛ به‌طوری‌که در تاریخ کاشت تأخیری (10آذر و 25آبان) عملکرد دانه در سطح 100کیلوگرم در هکتار نسبت به عدم‌مصرف کود به‌ترتیب حدود 55 و 60‌درصد افزایش یافت.

Changes in Southern Cotton and Peanut Producing Regions Relevance of the Topic Texas and Georgia are the major cotton and peanut producing states. These two crops compete for the same crop land, where peanuts usually rotate with cotton on a 3-4 year cycle (Texas Peanut Producers). The Farm Security and Rural Investment Act of 2002 shaped current farm policy, specifically enacted major changes to federal peanut policy. Prior to the 2002 farm bill, price supports and a quota system limited production, which elevated farm prices and supported farm income for peanuts (Shields, 2015). The 2002 policy allowed peanuts to follow the same policies as other program crops, where farm payments were made when the prices or crop revenue dropped below the guaranteed level (Shields, 2015). The Agricultural Act of 2014 introduced addition modifications to peanut farm policy. Produces are eligible to receive payments through either the Price Loss Coverage (PLC) or Agricultural Risk Coverage (ARC), but most producers chose to enroll in PLC. PLC payments depend on reference prices potentially making peanuts more attractive to plant than other covered crops, such as cotton. U.S. cotton production has been declining since its peak in the mid-2000s. This declining trend may be due to changes in farm policy, substitute products such as polyester, or changes in markets for substitute crops. In response to the WTO case between the U.S. and Brazil, The Agricultural Act of 2014 excluded cotton as a covered crop under both PLC and ARC, unless growers reallocated base acres—other than generic base (former cotton) acres—using a one-time option based on 2009-2012 plantings. Cotton producers also have the option for enrollment in Stacked Income Protection Plan (STAX), which is under Title XI: Crop Insurance of the 2014 farm bill. Currently cotton producers are requesting that cottonseed be considered as an “other oilseed” to offer assistance to the low cotton prices. Data and Methods Descriptive and graphical analysis of data focuses on USDA National Agricultural Statistics Service (NASS) yearly production, market and price data. Prices received by farmers are in nominal prices. The objectives of this research are to: 1) Describe current market trends in the U.S. cotton and peanut industries 2) Identify recent changes in farm policy for cotton and peanuts and 3) Discuss possible reasons for changes in production of both cotton and peanuts. Potential for Generating Discussion This analysis is presented in poster format and will generate substantial discussion between AAEA members. The visuals and results are interpreted through visual graphics of comparison between market trends and changing farm policies. Analytical reasoning and commodity market information provide explanations for potential changes in these commodity markets. References Farm Journal- Ag Web. Flood of Chinese Cotton Sends Prices Tumbling Most in Six Weeks. April 15, 2016. http://www.agweb.com/mobile/article/flood-of-chinese-cotton-sends -prices-tumbling-most-in-six-weeks-blmg/. Date Accessed: April 18, 2016. Shields, Dennis A. U.S. Peanut Program and Issues. Congressional Research Service. August 2015. Date Accessed: January 14, 2016. United States Department of Agricultural- Economic Research Service (USDA-ERS). Ash, Mark. Oil Crops Outlook. July 15, 2013. Date Accessed: April 19, 2016. United States Department of Agriculture- Farm Service Agency (USDA-FSA). Base Acre Reallocation, Yield Updates, Agricultural Risk Coverage (ARC) & Price Lose Coverage (PLC). 2014 Farm Bill Fact Sheet. September 2014. Date Accessed: January 14, 2016. United States Department of Agriculture- Foreign Agricultural Service (USDA-FAS). GATS database. United States Department of Agriculture- Risk Management Agency (USDA-RMA). Stacked Income Production Plan (STAX) for Upland Cotton. RMA Fact Sheet. August 2014. Date Accessed: December 18, 2015. United States Department of Agriculture- National Agricultural Statistical Service (USDA NASS). Quick Stats.

به‌منظور مطالعه واکنش عملکرد و کیفیت گلرنگ به مصرف گوگرد در تاریخ‌های مختلف کاشت، آزمایشی به‌صورت کرت‌های خُرد‌شده در قالب طرح بلوک‌های کامل تصادفی با سه تکرار در مزرعه تحقیقاتی دانشگاه کشاورزی و منابع طبیعی رامین خوزستان در سال زراعی 93-1392 اجرا شد. عوامل آزمایشی شامل تاریخ کاشت در چهار سطح (9‌آذر، 30‌آذر، 2‌بهمن و 12‌بهمن) به‌عنوان عامل اصلی و کود گوگرد به‌عنوان عامل فرعی در چهار سطح (صفر، 200، 400 و 600‌کیلوگرم در هکتار) از منبع گوگرد آلی گرانوله بودند. نتایج نشان‌داد که تأخیر در کاشت با کاهش تعداد دانه در کلاپرک و تعداد کلاپرک در بوته سبب کاهش عملکرد دانه شد. در تاریخ کاشت دیرهنگام 12‌بهمن نیتروژن دانه به‌میزان 17درصد افزایش، ولی درصد روغن کاهش نشان‌داد. بالاترین درصد روغن به‌میزان 25درصد از تاریخ 30‌آذر و مصرف 200‌کیلوگرم در هکتار گوگرد به‌دست آمد. بیش‌ترین عملکرد دانه به‌میزان 3590‌کیلوگرم در هکتار از تاریخ کاشت 30‌آذر حاصل شد. در کشت تأخیری 12‌بهمن عملکرد دانه به‌میزان 50/43درصد کاهش یافت. اما مصرف گوگرد به‌میزان 200کیلوگرم در هکتار در تاریخ کاشت 12بهمن عملکرد دانه را نسبت به شاهد 35درصد افزایش داد. هم‌چنین به‌علت بالا‌بودن عملکرد دانه در تاریخ کاشت 30آذر، بیش‌ترین عملکرد روغن هم از این تاریخ کاشت به‌دست آمد.

To improve the productivity and sustainability of cotton and cereals based system, direct sow ing under mulch was tested for its efficacy on cotton and maize yields on the research station of Farako - Bâ, in Western Burkina Faso. The experimental design was a complete randomized blocks of Fisher with four replications. Conventional tillage by annual moldboard plowing (T7) was compared with direct sowing under mulch -based cropping system (DMC) using maize association with cover crop s defined as: maize without cover crop (T1), maize +Brachiaria ruziziensis(T2), maize + B. ruziziensis+ Mucuna cochinchinensis (T3), maize + B. ruziziensis+ Panicum maximum (T4), maize + B. ruziziensis + Stylosantes hamata (T5), and maize + Crotalaria juncea (T6). Cover crops were planted 21 days after maize emergence between the rows of this main crop. The biomass produced by the cover crops and maize straws were evaluated as well as maize and cotton yields, during the first 6 years of the study, from 2010 to 2015. Results showed that among cover crops, the biomass production was significantly lower with C. juncea. The associations of cover crops with maize increased significantly the production of total dry matter compared to plots without cover crops, in the conventional tillage. Association with cover crops did not influence significantly nitrogen, phosphorus and potassium contents of maize and the maize?s yields even if the depressive effects were recorded. Compared to the conventional tillage, the DMC appeared also effective on seed cotton yields even without a significant improvement during the 6 first years of the study . These promising results, confirm the feasibility in tropical conditions of DMC which must be continued to better analyze its long-term effects on soil properties.

As práticas de mitigação da compactação do solo influenciam nos atributos do solo, mediante a isto, objetivou-se avaliar a rugosidade e taxa de cobertura do solo por plantas de cobertura, conduzidas sob preparos do solo. O experimento foi implantado em 2015, composto de cinco sistemas de preparos do solo: Plantio direto (PD); Plantio direto escarificado com intervalo de 3 anos (PDEi); Plantio direto escarificado anualmente (PDEa); Plantio direto sob preparo mínimo com intervalo de 3 anos (PDPMi) e Plantio direto sob preparo mínimo anualmente (PDPMa), realizados em maio, antecedendo a semeadura das plantas de cobertura: aveia, ervilhaca, nabo e consórcio das espécies (aveia, ervilhaca e nabo). O experimento é composto por um fatorial, com 3 repetições. Os parâmetros avaliados foram rugosidade do solo, taxa de cobertura do solo por palhada e planta, percentual de solo exposto até os 67 dias após a semeadura de plantas. O PD apresentou a menor variação de rugosidade do solo, cerca de 2,5 cm de alteração, enquanto para os demais tratamentos de preparos variaram de 3,6 – 4,4 cm. Para a taxa de cobertura por plantas pode-se observar o maior recobrimento do solo pela aveia preta e consórcios de espécies aos 15, 30 e 53 dias após a semeadura de plantas. O PDEa obteve maior percentual de solo inicial exposto, cerca de 71%, seguido do PDPMa, PDEi, PDPMi e PD. Os preparos com maior intensidade podem afetar características do solo e desempenho de plantas, bem como ocasionar a degradação ao longo do tempo.

In wet subtropical environments, perennial groundcovers are common in horticultural plantations to protect the soil from erosion. However, there has been little investigation into whether seeding annual cover crops into the perennial groundcovers provides additional soil services including carbon and nutrient cycling in these systems. To investigate this, farmer participatory field trials were conducted in commercial avocado, macadamia, and coffee plantations in the wet Australian subtropics. Cover crops were direct-seeded into existing inter-row groundcovers in winter (cool season cover crops), and into the same plots the following summer (warm season cover crops). Inter-row biomass was quantified at the end of winter and summer in the control (no cover crop) and cover crops treatments. Soil carbon and nutrient cycling parameters including hot water extractable carbon, water soluble carbon, autoclavable citrate-extractable protein and soil enzyme activities were quantified every two months from early spring (September) 2021 to late autumn (May) 2022. Seeded cover crops produced 500 to 800 kg ha−1 more total inter-row biomass over winter at the avocado coffee sites, and 3000 kg ha−1 biomass in summer at the coffee site. However, they had no effect on biomass production in either season at the macadamia site. Soil functional parameters changed with season (i.e., time of sampling), with few significant effects of cover crop treatments on soil function parameters across the three sits. Growing a highly productive annual summer cover crop at the coffee site led to suppression and death of perennial groundcovers, exposing bare soil in the inter-row by 3 weeks after termination of the summer cover crop. Annual cover crops seeded into existing perennial groundcovers in tree crop systems had few significant impacts on soil biological function over the 12-month period, and their integration needs careful management to avoid investment losses and exacerbating the risk of soil erosion on sloping lands in the wet subtropics.

This study was designed to investigate the paraquat toxicity toward root nodulation by Rhizobium on Macroptilium atropurpureum as an indicator plant. The legume was grown in Thornton medium treated with several concentrations of paraquat and inoculated with R.japonicum 143 (Rj-143) or Rhizobium sp. C-1.1. These bacteria represent cross-inoculation of soybean and cover-crops legumes, respectively. Nodule formation and Rhizobium population were measured periodically. At the end of planting time, nitrogenase activity of the nodules was analysis based on ARA (Acethylene Reduction Analysis) method. The results showed that nodules in plants inoculated with Rhizobium without addition paraquat, were formed within four weeks. There was no nodulation when paraquat was added. Paraquat was toxic to the plant, causing chlorosis, stunting, drying of the plant tissues, and death. The symptoms were detected at the second week after planting time. Paraquat also decreased Rhizobium population from 10^6 to 10^2 or 10^1 CFU/mL at 40 and 100 pp, respectively. These results depicted that paraquat disturbed the plant before nodulation, and at the same time Rhizobium populatin decreased until below minimal population required for nodulation. Therefore, the process of nodulation was disturbed, and in some treatments there was nodulation. It was concluded that paraquat was toxic to both plant and the Rhizobium, which cause nodulation failure.

A three-year experiment was conducted in Cullman, AL, to determine the impact of iron clay pea, sunn-hemp, soybean, velvet Bean, sorghum Sudan, and pearl millet cover crops terminated with two methods (rolling and flail mowing) on collard (brassica oleracea var. acephala, L.) yield. Overall, each of the three growing seasons (2013, 2014, and 2015) produced significant differences in cover crop biomass production among cover crops. Across three growing seasons sorghum Sudan and Pearl Millet generated the highest biomass (23,752 and 23,333 kg ha -1 respectively). During the same period, sunn hemp produced 10,908 kg/ha -1 and soybean, velvet bean and iron clay pea produced lower biomass (6,754, 6,068, and 4,360 kg ha -1 , respectively). Termination rates of cover crops used in this study were mostly below 90%. Termination rates above 90% have been recommended by agricultural extension services to plant cash crop into cover crop residue. In all three growing seasons volumetric soil moisture content during evaluation have showed that plots with rolled residue consistently held more VMC than the standing cover crops, indicating that rolled cover crop residue better preserved soil moisture content. Collard green yield was significantly different in each growing season for different covers and termination methods. Averaged over three growing seasons, the highest collard yield was observed for iron clay pea (12,623 kg ha -1 ), Velvet bean (11,020 kg ha -1 ) and sunn hemp (10,802 kg ha -1 ). Data suggest that higher collard yield was obtained with legume cover crops with the benefit of released nitrogen into the soil and utilized by collards. In addition, across all years, the average collard green yield was higher for cover crops which were flail mowed (11,875 kg ha -1 ) compared to rolled/crimped cover crops (7,349 kg ha -1 ).