Soil Cover Crops Research Articles

Soil health, cover crop, and fertility management: Nebraska producers’ perspectives on challenges and adoption

Cover crops (CC) and soil health management have been a prime focus in agriculture for many years, considering the demand for sustainable practices and production. However, CC adoption has not increased much compared to the promotion and wealth of scientific knowledge on using CC to improve soil health. Throughout the US Midwest, only 2.3% of the cultivated lands are sown to CC annually. This points toward the wide gap between scientific understanding and field-level adoption. In 2019/2020, the Nebraska Healthy Soils Task Force conducted a survey to determine the producers’ challenges and perspectives on adopting CC and other soil health and fertilizer management practices using a structured questionnaire. Of the total participants (<i>N</i> = 275), 64.0% (<i>n</i> = 176) were producers. About 80% (<i>n</i> = 133) of the total respondents (<i>N</i> = 193) grew CC to certain extents. Cover crop adoption was more in the eastern compared to western Nebraska. The challenges and motivations associated with CC and soil health were ranked using an index function constructed based on the Likert scale. The conflict in timing between the planting and termination of CC with the primary crop was ranked as the most significant challenge for producers (index score [IS] = 0.424, Rank = I). Cost-sharing support can help in wide CC adoption. In response to the motivating factors for adopting soil health management practices, producers ranked the reduction in topsoil erosion (IS = 0.480, Rank = I) the highest. In the fertility management, legume in the rotation primarily determines nitrogen (N), phosphorus (P), and potassium (K) application rates. Understanding field-level challenges and motivation will inform policy makers, educators, and conservationists in adapting their programs to provide better technical assistance, education, and support to producers to adopt soil health management practices.

A Multivariate Approach to Evaluate Reduced Tillage Systems and Cover Crop Sustainability

The evaluation of the effects of conservation agriculture during the transition from conventional tillage to no-tillage requires numerous indicators to be considered. For this purpose, we monitored changes in a multi-parameter dataset during a three-year experiment that combined three tillage intensities (conventional tillage—CT; minimum tillage—MT; and no tillage—NT) with three soil covering managements (tillage radish cover crop, winter wheat cover crop and bare soil). Using a multivariate analysis, we developed a Relative Sustainability Index (RSI) based on 11 physical (e.g., bulk density and penetration resistance), chemical (e.g., soil organic carbon and pH) and biological soil properties (e.g., earthworm density) to evaluate cropping systems sustainability. The RSI was most affected by tillage intensity showing higher RSI values (i.e., better performances) in reduced tillage systems. Specifically, the RSI under NT was 42% greater than that of CT and 13% greater than that of MT. Soil covering had little impact on the RSI. Among the tested parameters, the RSI was increased most by saturated hydraulic conductivity (+193%) and earthworm density (+339%) across CT and NT treatments. Our results suggest that conservation agriculture and, particularly, reduced tillage systems, have the potential to increase farm environmental and agronomic sustainability.

Comparing Sensor-Based Adjustment of Weed Harrowing Intensity with Conventional Harrowing under Heterogeneous Field Conditions

Setting the right intensity is crucial for the success of post-emergence weed harrowing in cereals. The percentage of crop soil cover (CSC) correlates with the selectivity of weed harrowing. Therefore, real-time camera-based measurements of CSC offer a novel approach to automatically adjust the intensity of harrowing. The intensity of harrowing is varied by hydraulic steering of the tine angle. Five field experiments in cereals were conducted at three locations in southwestern Germany in 2019 and 2020 to measure the effect of camera-based harrowing (2020) and conventional harrowing on weed control efficacy (WCE), crop density, and grain yield. For this purpose, pair-wise comparisons of three fixed harrowing intensities (10°, 40°, and 70° tine angle) and three predefined CSC thresholds (CSC of 10%, 20%, and 60%) were realized in randomized complete block designs. Camera-based intensity adjustment resulted in more homogeneous CSC across the whole plot (6–16% less standard deviation variation) compared to conventional fixed settings of the tine angle. Crop density, WCE, crop biomass, and grain yield were significantly higher for camera-based harrowing than for conventional harrowing. WCE and yields of all automatic adjusted harrowing treatments were equal to the herbicide control plots. Camera-based harrowing provides a robust technology for effective weed management with a lower risk of crop damage than conventional harrowing.

INFLUENCE OF SOIL TREATMENT ON THE NUMBER OF EARTHWORMS AND THE SIZE OF MICROBIAL BIOMASS UNDER THE CONDITIONS OF AGRICULTURAL INTENSIFICATION

Objective. To establish the influence of soil treatment methods on the number of earthworms and microbial biomass in dark-chestnut heavy loam soil with observance of the following crop rotation: soybean – winter wheat – corn; verify the hypothesis of the negative influence of traditional soil treatment technologies on the number of earthworms. Methods. Analytical, field, laboratory, system analysis, statistical. Results. During the studies conducted in 2018–2021 at Askanian State Agricultural Experimental Station of the Institute of Irrigated Agriculture of the NAAS, the positive influence of zero soil treatment technologies on the studied parameters versus with traditional technologies was established. A 2.5-fold increase in the number of earthworms and a 1.1-fold increase in microbial biomass was reported with zero soil treatment technologies. The interaction between soil treatment factors and cover crops in the structure of crop rotation was 23.7 %. Soil treatment technologies had a negligible influence on the size of microbial biomass — at the level of 1.4 %. The significance of the action of cover crops in crop rotation was 10.0 %. The experiment also showed a higher number of earthworms in the soil with zero soil treatment technologies with cover crops and traditional technologies for control, due to better live environment and favourable conditions for reproduction and distribution of the population depending on soil treatment technologies. Changes in the density of the soil layer 0–30 cm were within the measurement error (for zero soil treatment technologies the studied parameter was 1.23 g/cm3, for traditional — 1.24 g/cm3). Compaction of 0–20 cm soil layer with zero and traditional soil treatment technologies was reported. The content of soil organic matter by the years of studies under zero soil treatment technologies increased to 3.0 %, which is 1.2 times higher than with traditional technologies. Conclusion. Under the conditions of stationary field experiment the positive influence of zero soil treatment technologies on early changes of biological properties of soil, which were characterized by increase in number of earthworms and size of microbial biomass, has been established. The positive influence of cover crops on soil quality was determined, which was characterized by signs of biota activation in the 0–30 cm layer and improvement of biological and physical properties of the soil.

Cover Crop Soil Legacies Alter Phytochemistry and Resistance to Fall Armyworm (Lepidoptera: Noctuidae) in Maize.

Plant-soil feedbacks can mediate aboveground plant-herbivore interactions by impacting plant chemistry. Given that soil legacies and agricultural practices are closely tied, a better understanding of soil legacy cascades and their application in pest management are needed. We tested how cover crop legacies alter resistance to fall armyworm (Spodoptera frugiperda Smith, Lepidoptera: Noctuidae) in maize (Zea mays L., Poales: Poaceae). We compared herbivore performance and behavior of fall armyworm larvae on maize grown after four cover crop treatments: a leguminous mycorrhizal cover crop (pea: Pisum sativum L., Fabales: Fabaceae), a nonleguminous mycorrhizal cover crop (triticale: x Triticosecale Wittm. Ex A. Camus, Poales: Poaceae), a nonleguminous nonmycorrhizal cover crop (radish: Raphanus sativus L., Brassicales: Brassicaceae), and no cover crops (fallow). Soil inorganic N was highest in pea treatments and lowest in triticale treatments, while maize AMF colonization was greatest when grown after mycorrhizal cover crops compared to nonmycorrhizal or no cover crops. Cover crop legacies altered the emission of maize volatiles and fall armyworm larvae oriented toward odors emitted by maize grown after radish more frequently than triticale in olfactometer assays. Additionally, larvae performed better and consumed more leaf tissue when feeding on maize grown after radish and poorest on plants grown after triticale. When damaged by fall armyworm, maize grown after triticale expressed higher levels of lipoxygenase-3 (lox3), while plants grown after radish upregulated maize proteinase inhibitor (mpi) gene expression. Our results highlight the importance of appropriate cover crop selection and suggest that triticale could strengthen maize resistance to fall armyworm.

Soybean Relative Maturity, Not Row Spacing, Affected Interseeded Cover Crops Biomass

Adoption of cover crop interseeding in the northwestern Corn Belt in the USA is limited due to inadequate fall moisture for establishment, short growing season, additional costs, and need for adapted winter-hardy species. This study evaluated three cover crop treatments—no cover crop, winter rye (Secale cereale L.), and winter camelina (Camelina sativa (L.) Crantz)—which were interseeded at the R6 soybean growth stage, using two different soybean (Glycine max (L.) Merr.) maturity groups (0.5 vs. 0.9) and two row spacings (30.5 vs. 61 cm). The objective was to evaluate these treatments on cover crop biomass, soil cover, plant density, and soybean yield. Spring wheat (Triticum aestivum L.) grain yield was also measured the following year. The early-maturing soybean cultivar (0.5 maturity) resulted in increased cover crop biomass and soil cover, with winter rye outperforming winter camelina. However, the early-maturing soybean yielded 2308 kg·ha−1, significantly less compared with the later maturing cultivar (2445 kg·ha−1). Narrow row spacing had higher soybean yield, but row spacing did not affect cover crop growth. Spring wheat should not follow winter rye if rye is terminated right before seeding the wheat. However, wheat planted after winter camelina was no different than when no cover crop was interseeded in soybean. Interseeding cover crops into established soybean is possible, however, cover crop biomass accumulation and soil cover are limited.

Cover crops combined with soil tillage impact the spontaneous species density, richness and diversity in banana cover cropping systems

Soil tillage and cover crops impact spontaneous vegetation in agrosystems. Soil tillage destroys seedlings and can affect the soil seedbank. Cover crops compete with naturally occurring spontaneous species. Our aim was to gain insight into how soil tillage (here, the false seedbed technique) and cover crops impact the spontaneous vegetation in fallows preceding banana crops. In a fallowed field in Guadeloupe (French West Indies), two factors were combined in a split-plot design: the soil tillage modality before cover crop sowing (with or without the false seedbed technique) and the cover crop species (Crotalaria spectabilis, Pueraria phaseoloïdes, a 50/50 mix of Brachiaria decumbens + Brachiaria ruziziensis, a spontaneous vegetation control). On a monthly basis, in three permanent quadrats per sub-plot, all spontaneous species were identified and their numbers counted, while calculating the species richness and Shannon’s diversity index. The spontaneous vegetation dynamics contrasted depending on the treatment. From 7 months post-sowing the species density, richness and Shannon index were significantly lower in treatments with B. decumbens + B. ruziziensis and P. phaseoloïdes, while in treatments with C. spectabilis, the species density and richness were significantly higher with than without the false seedbed technique. These effects were probably related to differences in the competitive ability of the cover crop used and, to a lesser extent, to the false seedbed effects on the soil seedbank. This is the first study to show that under a tropical climate, sown cover crop species combined with different soil tillage modalities have substantial impacts on the species density, richness and diversity of the spontaneous plant community over a 1-year period. These results could help farmers in their weed control strategies by providing them with a deeper understanding of the effects of practices on the spontaneous plant community.

Modeling cover crop biomass production and related emissions to improve farm-scale decision-support tools

CONTEXTCover crops deliver numerous ecosystem services including the capacity to sequester and store atmospheric CO2 offering promise as a natural climate solution. Farm system models must be able to accurately represent cover crop systems and estimate the associated net greenhouse gas emissions from this practice across agricultural contexts. OBJECTIVEThe objectives of this study were to: (1) parameterize new and existing cover crop species for DayCent – the biogeochemical model behind the decisions-support tool, COMET-Farm – using published data on cover crop biomass production, (2) validate differences between cover crop and control systems using published and long-term data from across the U.S. for SOC and N2O emissions, and (3) evaluate model performance and discuss improvements to cover crop data reporting to facilitate future testing. METHODSWe used published field experiment datasets from across the U.S. to estimate cover crop biomass production, SOC, and soil N2O emissions. We parameterized one new cover crop species in the model – sunn hemp (Crotalaria juncea L.) – and revised the parameters for existing model cover crop species using new biomass observations. We also validated the ability of the model to estimate changes in SOC and soil N2O emissions relative to a no cover crop control using empirical observations. RESULTS AND CONCLUSIONSFor data sets used in parameterization, DayCent reasonably captured observed trends in aboveground biomass C, N, and C:N ratios across six different cover crop species and mixtures, explaining 25–69%, 14–58%, and 29–50% of the variation, respectively, with a few exceptions. Using a smaller validation dataset for a subset of these cover crop species – cereal rye (Secale cereale L.) and vetch (Vicia spp.) – the model demonstrated less agreement between modeled and observed aboveground biomass. For SOC model validation, the observed mean SOC difference between cover crop and control treatments was 178.4 g m−2 and the mean modeled difference was 158.2 g m−2. Observed soil N2O emissions were highly variable impacting model performance, but DayCent did capture the general trend from field measurements for cover crops to suppress soil N2O emissions. SIGNIFICANCEOur results demonstrate that even under limited data availability, process-based models like DayCent can inform on farm-scale biogeochemical processes under cover cropping. These findings are critical as cover crops are more widely adopted in the United States for their climate and environmental benefits. However, more detailed reporting from empirical studies will improve model estimates and reduce uncertainty, particularly data pertaining to farm management, soil, climate, and location.

Management of Eleusine indica and Digitaria insularis with Herbicides in Association with Cover Plants

Aims: This study aimed to evaluate the control of Eleusine indica Gaertn. and Digitaria insularis (L.) Fedde through the combination of soil cover with green manure straw and herbicides applied in pre-emergence.&#x0D; Study Design: Each weed species was evaluated in different experiments. The experiments were set up in a greenhouse in a completely randomized design and arranged in a factorial scheme (5×4)+2, with four replications.&#x0D; Place and Duration of Study: Center of Agricultural Sciences, São Paulo, Brazil, from May 2019 to May 2020.&#x0D; Methodology: Seeds of Digitaria insularis and Eulesine indica were sown at a depth of 1 cm from the soil surface. Then, the pots were watered, and the straw of Cajanus cajan, Sorghum bicolor, Crotalaria juncea, Crotalaria spectabilis, and Crotalaria breviflora was deposited on the surface. The pre-emergence herbicides trifluralin (900 g ai ha−1), pendimethalin (1200 g ai ha−1), clomazone (1000 g ai ha−1), and s-metolachlor (1920 g ai ha−1) were applied one day after the weed seeds were sown. The percentage of weed control was evaluated at 10, 20, and 30 days after emergence (DAE). The plant shoot was cut at 30 DAE and the weight of dry biomass was determined. The control without herbicide and with soil cover crop and no herbicide and no soil cover were also evaluated.&#x0D; Results: Sorghum bicolor, Cajanus cajan, and Crotalaria breviflora were the most effective in controlling Eleusine indica when no herbicide was applied. Only Sorghum bicolor showed a satisfactory control of Digitaria insularis without the use of chemical management (above 80%). The association of pre-emergence herbicides with soil cover showed high control of weeds.&#x0D; Conclusion: The results showed that the association between chemical and cultural methods is an effective alternative to control Eulesine indica and Digitaria insularis.

Cover crop enzyme activities and resultant soil ammonium concentrations under different tillage systems

Increased interest in managing agroecosystems for soil health has led to adoption of conservation management practices such as cover cropping and no-tillage. There is a dearth of knowledge surrounding cover crop residue N cycling and release, impacting subsequent N availability for the cash crop after cover crop termination. The microbial degradation of plant material and subsequent nutrient release is mediated by extracellular enzymes. This study used litter bag methodology to investigate the enzyme activities of three cover crop residues (cereal rye (CR) (Secale cereale L.), hairy vetch (HV) (Vicia villosa Roth), and a CR/HV mixture) in two tillage systems (no-tillage and reduced tillage) during the cover crop decomposition period in a corn (Zea mays L.) agroecosystem. The dynamics and amounts of β-glucosidase (EC 3.2.1.21) and urease (EC 3.5.1.5) enzyme activities on cover crop residue were quantified to determine if enzyme activities or stoichiometry are dependent on litter quality or can indicate N cycling potential. Results revealed that cover crop and tillage significantly impacted urease and β-glucosidase residue enzyme activity dynamics and amounts (p < 0.05). β-glucosidase activity of CR, HV, and a CR/HV mixture decreased by 76 %, 81 % and 77 % during the 2016 decomposition period, respectively. On average, urease activities of cover crop residues and soil ammonium concentrations increased during this period. In 2017, urease activities significantly decreased in all treatments (p < 0.05). β-glucosidase enzyme activity significantly decreased from 38 days after termination to 123 days after termination in all cover crop and tillage treatments (p < 0.05). Urease activities were significantly higher in the tillage treatments compared to no-tillage at the beginning of the 2017 decomposition period (p < 0.05). Soil ammonium concentrations significantly increased by 38 % across all treatments in 2017 during the decomposition period and concentrations were 12 times higher in 2017 at corn maturity compared to 2016. These results indicate potential for cover crops to stimulate residue β-glucosidase activity, suppress urease activity and ammonification, and increase soil N immobilization during corn N demanding growth stages. Furthermore, this study indicates that growers should consider optimum cover crop winter biomass accumulation levels to avoid potential N immobilization.

Quantifying Root-Soil Interactions in Cover Crop Systems: A Review

Plant roots are an integral part of soil ecosystems and contribute to various services, including carbon and nutrient cycling, weathering, and soil formation. They also modify soil physical properties (e.g., soil water content, pore size distribution, and bulk density) and impact subsequent crops’ growth. Cover crops have been reported to improve soil and environmental quality by reducing nutrient losses, improving soil water content, and increasing soil organic matter. Understanding the complex interactions between cover crop roots and soil (RS) is of utmost importance. However, cover crop RS interactions have not been critically reviewed. In this article, we investigated the nature of cover crop physical RS interactions and explored the emerging technologies for their study. We also assessed technologies that may be readily applied to the study of physical RS interactions in cover crop systems and discussed ways to improve related research in the future.

Dryland cover crop soil health benefits are maintained with grazing in the U.S. High and Central Plains

Cover crops are important for soil conservation efforts but can compete with cash crops for limited water in dryland agricultural systems. Grazing cover crops may provide additional income to improve the profitability of cover cropped systems, but the effect of grazing cover crops on soil health remains poorly understood in semi-arid regions. We conducted on-farm research to examine the short-term effects of grazed and un-grazed spring-planted cover crops compared to full summer fallow on soil health metrics and wheat yields across ten no-till, dryland producer fields over two years in eastern Colorado, western Kansas and western Nebraska, USA. Soils were evaluated at cover crop termination following two to three months of growth for differences in a suite of soil physical and chemical properties. Grazed and un-grazed cover crops increased soil aggregation relative to summer fallow by 30−50%. Surface bulk density (0−5 cm) decreased by 4% with un-grazed cover crops, while bulk density under grazed cover crop was similar to fallow. Soil moisture in the top180 cm depth was reduced by 4–22 % with cover crops, with the greatest water depletion occurring below 30 cm, and grazing did not appear to affect soil moisture compared to un-grazed cover crops. Both cover crop treatments reduced wheat yields by roughly 20 %. The short-term improvements to key soil health metrics with cover crops were largely maintained with grazing, indicating the potential for livestock integration as a management option to offset the short-term yield impacts of cover crop moisture use in water-limited environments.

Effect of Soil Management and Training System on Negroamaro Wine Aroma.

This study aimed to assess the impact of two soil managements and training systems on yield and wine aroma compounds of Negroamaro variety grown in a warm climate region (southern Italy). Cover crop (CC) and soil tillage (ST) as soil management, whilst bilateral Guyot (BG) and monolateral Guyot (MG) as training systems were compared. Free and bound volatile fractions were evaluated by GC-MS. ST and CC as well as BG and MG significantly affected yield parameters. In particular, yield was higher in ST and BG than in CC and MG, respectively; moreover, it was found to be positively influenced by interaction between BG and ST. Regarding aroma compounds, significant interactions between soil management and training system factors were observed. In case of free volatiles, the most positive interaction was found between BG and ST, whereas, for bound volatiles, the best interaction was represented by MG with both soil tillage and cover crop. Vine leaf area and development over vine growth stages along with water stress levels played an important role in determining the aroma profile as well as yield parameters. In conclusion, the training system significantly interacted with soil management and affected most of important aroma compounds in Negroamaro wine.

Nutrient stoichiometry of a plant-microbe-soil system in response to cover crop species and soil type

AimsThe theory of ecological stoichiometry mostly builds on studies of natural terrestrial ecosystems, whereas only limited stoichiometry information is available in response to agronomic practices.MethodsWe designed a greenhouse experiment in order to disentangle the specific role of cover crop identity and soil characteristic in affecting nutrient stoichiometry of a plant-microbe-soil system.ResultsNutrient ratios of cover crop biomass were species-specific and the growth rate explained, for most species considered, the stoichiometric differences in response to soil type. In contrast, the nutrient stoichiometry of soil microbes was more homeostatic and did not respond to either cover crop identity or soil type. Compared to bare soil, the presence of cover crop enhanced microbial phosphorus immobilization in the clay-rich soil, whereas it promoted microbial carbon biomass and microbial nitrogen immobilization in the sandy-rich soil. A greater microbial cumulative respiration in clay soils, where a higher microbial biomass C at the beginning of the incubation was observed, suggested a major role of soil type, compared to cover crop identity, in affecting microbial metabolism.ConclusionsBy understanding the stoichiometric constraints in the plant-microbe-soil system, our findings can help to implement agro-ecological practices by selecting appropriate cover crop species in relation to soil type in order, for example, to avoid nutrient limitation due to microbial nutrient immobilization.

Combinations of Plant Species for Rotation With Onion Crops: Effects on the Light Fraction, Carbon, and Nitrogen Contents in Granulometric Fractions of the Soil Organic Matter

The conversion of conventional tillage system (CTS) into no-tillage system (NTS) for onion crops with use of soil cover crops increases carbon and nitrogen contents in the soil aggregates. The objective of this work was to evaluate the effects of combinations of different plant species and soil management systems using rotation with soil cover crops for onion crops on the light organic matter (LOM), carbon (C), and nitrogen (N) contents in the organic matter granulometric fractions in soil macroaggregates and bulk soil. A nine-year experiment (2007-2016) was conducted using the treatments (T): maize-onion in NTS (T1); soil cover crops (winter)-onion in NTS(T2); maize-winter grasses-onion in NTS (T3); velvet bean-onion in NTS (T4); millet-soil cover crops (winter)-onion in NTS (T5); velvet bean-rye-onion in NTS (T6); maize-onion in CTS (T7); intercropped soil cover crops (summer)-onion in NTS (T8). C and N contents in the LOM, particulate organic C and N (POC and PON), and mineral- associated C and N (MOC and MON) were evaluated in soil macroaggregates (8.0 to 2.0 mm) and bulk soil (&lt;2.0 mm) from the 0–5 cm, 5–10 cm, and 10–20 cm layers. High diversity and combinations of plant species in T2-T6, and T8 resulted in higher POC and MON contents in aggregates, and higher MOC and PON contents in bulk soil, when compared to T1 and T7. T2 was a better option to increase LOM and POC contents in aggregates (0-5 cm). The evaluation of POC (0–5 cm), PON, and MON (0-10 cm) contents in soil aggregates showed more significant differences between the treatments than the contents found in bulk soil. The onion crops under NTS combined with use of rotations with soil cover crops were more efficient to improve the evaluated soil attributes than those under CTS.

Cover crops reduce soil resistance to penetration by preserving soil surface water content

Replacement of bare fallow in rotations by cover crops is a promising tool to reduce crusting, although the interactions with the soil moisture and the effect of the cover crop species are still not well understood. The objective of this work was to determine how cover crops modify the soil surface response to penetration and their relation with the soil water content. Two winter cover crops, barley (Hordeum vulgare L.) and vetch (Vicia sp. L.), were compared with a bare fallow treatment in a 10-year field experiment in central Spain. Soil resistance to penetration and soil water content were intensively measured (76 sampling dates) at two surface depths, using two types of surface penetrometers. Under the barley cover crop, the number of very dry events was reduced by around 20%, compared to the bare fallow. The soil resistance to penetration was closely related to the surface soil water content (R2 = 0.65) and cover crops affected it through soil moisture modification. In this line, the greater mulch provided by barley cover crop respect to vetch, increased the soil water content prior to main crop seeding, resulting in less resistance to penetration during this critical period. The good performance of barley resulted in a reduction of more than 60% of the soil resistance to penetration between the 3rd and 8th year of the experiment (7.2–2.9 kg cm−2, respectively). Even under bare fallow, soil strength was decreased after ten years with reduced tillage. Therefore, the maintenance of cover crop residues over surface soil together with reduced tillage enhanced the soil surface conditions and steadily reduced the risk of crust formation. Expected enhancement of main-crop germination, water infiltration, soil aeration and erosion mitigation may be attained by cover-cropping in degraded soils.

Cover crop influence on soil water dynamics for a corn–soybean rotation

AbstractCrop production is reduced by insufficient and/or excess soil water, which can significantly decrease plant growth and development. Therefore, conservation management practices such as cover crops (CCs) are used to optimize soil water dynamics, since CCs can conserve soil water. The objective of this study was to determine the effects of CCs on soil water dynamics on a corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation at three soil depths over 3 yr. The study was conducted at the Chariton County Cover Crop Soil Health Research and Demonstration Farm (CCSH) in Missouri. Initial CC establishment occurred in 2012. Volumetric soil water content (VWC) was monitored at 15‐min intervals with calibrated Waterscout SM100 soil moisture sensors (Spectrum Technologies) at three depths (10, 20, and 30 cm) in 2016, 2017, and 2018. Cover crop soils maintained numerically higher VWC values compared with no CC (NCC) at both 10‐ and 20‐cm depths throughout the study period where the differences were significant in some weeks. The subsurface soil water recharge was greater in CC soils at both 10‐ and 20‐cm depths compared with NCC in March 2017. The results imply that CC soils have maintained higher VWC levels during vegetative period of the CC growth where the differences were significant in some weeks compared with NCC at all three soil depths. These findings can be used to promote CC adoption for better soil water storage and develop CC management plans for corn–soybean rotations on claypan soils.

Influence of Recurrent Rolling/Crimping on Cover Crop Termination, Soil Strength and Yield in No-Till Cotton

Rollers/crimpers have been used to terminate cover crops typically with supplemental herbicide application to speed-up termination. Due to environmental concerns, there is a need to reduce herbicide use. In the Southern USA, the cash crop is typically planted three weeks after a rolled cover crop reaches more than 90% kill rate which eliminates competition with the cash crop for water and nutrients. A three-year replicated field experiment was initiated in the fall of 2014 to determine the effects of recurring rolling by experimental rollers/crimpers in terminating a cereal rye cover crop in central Alabama and how multiple rolling affected soil strength. Experimental 2-stage (one smooth drum and one crimping drum), 4-stage (one smooth drum and three crimping drums), spiral, and smooth rollers were tested to roll rye 1, 2, and 3 times (conducted at the same day). A smooth roller with mounted spray boom applying glyphosate rolling once was also evaluated, and untreated rye was the control. Rye was terminated at the milk growth stage and was evaluated one, two and three weeks after rolling. At one week after rolling, the highest rye kill rate was obtained with rolling three times by the 4-stage (96%), 2-stage (92%), spiral roller (81%); rolling once by the smooth roller with glyphosate (94%) compared to the untreated rye at 37%. At two weeks after rolling no differences among rollers were found (91% to 98%); the untreated rye was 54%. Similarly, at three weeks after rolling no differences were detected among rollers (99% to 100%); the untreated rye was 86%. Rolling 2 or 3 times compared with rolling one time did not cause soil compaction. However, at the 15 cm depth cone index (CI) did exceed 2 MPa (a critical value of root penetration restriction); although this CI increase was solely related to decrease in gravimetric soil moisture content (GMC). In addition, over three growing seasons, the seed cotton yield was not affected by rolling treatments with the average yield of 3601 kg ha−1 (1512 kg ha−1 of cotton lint).

Sugarcane root system: Variation over three cycles under different soil tillage systems and cover crops

Machinery traffic combined with soil management processes in the establishment of sugarcane areas degrades the soil structure, limiting root development and yield of the crop. The use of conservation tillage systems and cover crops can reduce such effects and improve its soil physical quality. Therefore, a field study was conducted over three agricultural years to assess the development of the sugarcane root system planted under different soil tillage systems and cover crops during three crop cycles. The study was carried out in 2014 in Ibitinga (São Paulo, Brazil) in an experimental design in split-plot scheme, with three repetitions and three soil tillage systems (no-tillage, minimum tillage and minimum tillage with deep subsoiling) combined with four cover crops (sorghum, millet, peanut and sunn hemp), plus one control treatment consisting of conventional tillage and no cover crop use. The root system attributes (dry biomass, density, volume, length, and surface area) were evaluated every three months during the 2015/2016, 2016/2017, 2017/2018 crop years, in the 0.0−0.2 m, 0.2−0.4 m and 0.4−0.6 m layers. Although few significant differences were obtained in the root system of the sugarcane between the different soil tillage systems and use of cover plants, the accumulation of roots was evidenced during the second cycle of the crop, mainly due to the contribution of new roots, arising from the ratoons of the plants. Differences in the dry biomass of the roots were obtained in the minimum and minimum tillage with deep subsoiling, only at the time of harvesting the first crop cycle (cane plant, 395 days after planting) and in the second cycle, 665 days after planting. The highest concentration of root dry biomass was obtained in the 0.0−0.2 m surface layer, containing between 36 % and 62 % of roots. However, the significant differences of root dry biomass between the soil tillage and cover crops occur in the clayey layer at 0.30−0.6 m, where the management effects affected the root system. During the first three sugarcane cycles, the 0.0−0.2 m surface layer concentrated the highest amount of dry biomass of the roots, representing between 36 % and 62 % of the roots present in the first 0.6 m deep.

Smart Harrowing—Adjusting the Treatment Intensity Based on Machine Vision to Achieve a Uniform Weed Control Selectivity under Heterogeneous Field Conditions

Harrowing is mostly applied with a constant intensity across the whole field. Heterogeneous field conditions such as variable soil texture, different crop growth stages, variations of the weed infestation level, and weed species composition are usually not considered during the treatment. This study offers a new approach to sensor-based harrowing which addresses these field variations. Smart harrowing requires the continuous adaptation of the treatment intensity to maintain the same level of crop selectivity while ensuring a high weed control efficacy. Therefore, a harrow was equipped with a sensor-system to automatically adjust the angle of the harrow tines based on a newly developed decision algorithm. In 2020, three field experiments were conducted in winter wheat and spring oats to investigate the response of the weed control efficacy and the crop to different harrowing intensities, in Southwest Germany. In all experiments, six levels of crop soil cover (CSC) were tested. The CSC determines the balance between crop damage and weed removal. Each experiment contained an untreated control and an herbicide treatment as a comparison to the harrowing treatments. The results showed an increase in the weed control efficacy (WCE) with an increasing CSC threshold. Difficult-to-control weed species such as Cirsium arvense L. and Galium aparine L. were best controlled with a CSC threshold of 70%. However, 70% CSC caused up to 50% crop biomass loss and up to 2 t·ha−1 of grain yield reduction. With a CSC threshold of 20% it was possible to control up to 98% of Thlaspi arvense L. The highest crop biomass, grain yield, and selectivity were achieved with an CSC threshold of 20–25% at all locations. With this harrowing intensity, grain yields were higher than in the herbicide plots and a WCE of 68–98% was achieved. Due to the rapid adjustment of tine angle, the new sensor-based harrow allows users to apply the most selective harrowing intensity in every location of the field. Therefore, it can achieve equal weed control efficacies as using herbicide applications.