Single Cover Crops Research Articles

Cover crops improve soil structure and change organic carbon distribution in macroaggregate fractions

Abstract. Soil structure is sensitive to intensive soil management. It can be ameliorated by a reduction in soil cultivation and stimulation of plant and microbial mediators for aggregate formation, with the latter being a prerequisite and measure for soil quality. Cover crops (CCs) are part of an integrated approach to stabilize or improve soil quality. Thereby, the incorporation of diverse CC mixtures is hypothesized to increase the positive effects of CC applications. This study entailed an investigation of the legacy effect of CCs on soil aggregates after three crop rotations in the second main crop (winter wheat) after the last CC treatment. Four CCs (mustard, phacelia, clover, and oat) cultivated in pure stands and with a fallow treatment were compared to a mixture of the four CC species (Mix4) and a highly diverse 12-plant-species mixture (Mix12) in a long-term field experiment in Germany. The organic carbon (OC) distribution within macroaggregate fractions (16–8, 8–4, 4–2, 2–1, and <1 mm) and their aggregate stability were measured by dry- and wet-sieving methods, and the mean weight diameter (MWD) was calculated from water-stable aggregates. The results showed that, compared to the fallow, all CCs increased the MWD between 10 % and 19 % in soil under the following main crop. The average MWD increase over the fallow was slightly higher for CC mixtures (16 %) than for single CCs (12 %). Most of the OC (67.9 % on average) was stored in the <1 mm aggregate fraction, highest in the topsoil and decreasing with soil depth. The intermediate fractions (8–4 mm, 4–2 mm, 2–1 mm) stored 8.5 %, 10.5 %, and 11.0 % of the total OC, while 2.1 % was stored in the 16–8 mm fraction. Higher MWD improvement at the 20–30 cm depth also indicates additional benefits from a reduction in the cultivation depth. Structural equation modelling (SEM) suggests that single CCs were more likely to increase OC storage in small macroaggregates <1 mm, while CC mixtures were more likely to increase OC in the largest fraction (8–16 mm). Different individual CC species or mixtures exhibited varying involvement in the formation of different aggregate fractions. We provide evidence that litter quality, root morphology, and rhizosphere input, which affect microbial mediators of aggregate formation, might be the main reasons for the observed differences between CC treatments. Cover crops are valuable multifunctional tools for sustainable soil management. Here, we showed that they contribute to structure amelioration in arable soils. Increasing the functional diversity of plant species in CC mixtures could be a strategy to further enhance the positive effects of CCs in agroecosystems.

Long-term effects of cover crops on physical-hydric properties of compacted soil

The screening of cover crops is essential for improving the physical-hydric properties of compacted soils. This study aimed to evaluate the effects of mixed or single cover crops on improving the physical-hydric properties of compacted Oxisol. Species with tap-rooted and fibrous-rooted rooting patterns were evaluated. The species included pearl millet (Pennisetum americanum), pigeon pea (Cajanus cajan), sunn hemp (Crotalaria spectabilis), velvet bean (Mucuna pruriens), white oat (Avena sativa), black oat (Avena strigosa), rye (Secale cereale), black oat + forage turnip (Raphanus sativus), black oat + white lupin (Lupinus albus L.), and black oat + group pea (Pisum arvense L.). Mixing cover crops did not improve the physical properties of the soil. The tap-rooted pigeon pea effectively reduces bulk density and increases porosity and saturated hydraulic conductivity (Ksat) in compact soils. The selection of cover crops with characteristics that improve soil physical-hydric properties is crucial for compacted areas.

Growing cover crop mixtures are more sustainable than single cover crop in continuous cotton cropping: Comprehensive assessment from 3-year field experiment

Cover cropping combined with nitrogen (N) application reduction is considered as an attractive practice due to increasing resources use efficiency while improving soil health and cash crop productivity. Yet comprehensive assessment studies have rarely been reported from energy, environmental, economic and ecological perspectives under different cover cropping systems. Therefore, a field experiment was conducted during 2019–2022 with four N application rates (i.e., 0 (N0), 112.5 (N1), 168.75 (N2) and 225 (N3, as a control) kg N hm−2) under four cover cropping systems (i.e., continuous cotton (CC), Orychophragmus violaceus with cotton (OC), Vicia villosa with cotton (VC), and an Orychophragmus violaceus and Vicia villosa mixture with cotton (MC) relay intercropping). Field observations were incorporated into a life cycle assessment to evaluate the environmental footprint, energy flow, ecosystem service value and economic and ecosystem economic benefits. Relay intercropping cover crops can reduce the carbon footprint per unit area (CFa) by 36.7%, increase the ecosystem service value by 64.4% and ecosystem economic benefits by 7.8% compared with the CC system, in which MC system had better performance than OC and VC systems at above aspects. N application rates notably increased net energy, CFa, NFa, ecosystem service value, and ecosystem economic benefits. After considering the comprehensive index of energy, environment, the economy and the ecosystem economy, the sustainability performance index of MCN2 (Orychophragmus violaceus and Vicia villosa mixture/cotton relay intercropping with 168.75 kg N hm−2) combination increase by 51.7% compared to all treatments average. Taken together, the study results demonstrated that introducing cover crop mixture into monoculture cotton was more sustainable and cleaner cotton production practice than sing cover crop or fallow in the Yellow River basin and other regions with similar ecological conditions.

Use of winter cover crops improves maize productivity under reduced nitrogen fertilization: a long-term study

ABSTRACT The objective was to evaluate the effect of winter cover crops on the agronomic performance of maize during five crop seasons in a clayey Inceptisol with reduced mineral nitrogen (N) inputs. The treatments were seven single cover crops: white oats (Avena sativa L.), black oats (Avena strigose Schreb.), ryegrass (Lolium multiflorum L.), canola (Brassica napus L.), vetch (Vicia sativa L.), fodder radish (Raphanus sativus L. and red clover (Trifolium pratense L.); a mix (black oats + vetch and a fallow. During summer, in succession to the cover crops, maize was grown under no-tillage. The attributes were evaluated in two stages of maize development: flowering (morphological components and physiological maturation (yield components). Differences in morphologica and yield variables were observed in all crop seasons, with emphasis on grain yield, number of grains per row (NGR and ear length (EL). The use of vetch showed greater contribution to the development of maize in relation to the other cover crops used, promoting an increase in stem diameter (SD), E and NGR in all crop season and directly reflecting in higher grain yield. On the other hand, when maize was grown under cover crops commonly used in southern Brazil, such as ryegras and white oats, the yield was similar to fallow. The results showed that vetch promoted higher maize yields, probably by N mineralization and reinforce the hypothesis that cover crops in the off-season can aggregate benefits to crops in succession, especially in terms of nutrition.

Weed Control Ability of Single Sown Cover Crops Compared to Species Mixtures

To achieve efficient weed control through cover cropping, the plant species chosen needs particular consideration. Combing different cover crop (CC) species in mixtures may increase the number of provided ecosystem services, including reliable suppression of weeds. We tested the weed suppression ability of single CC species and CC mixtures in a field trial during the autumn-to-winter growing season of 2016 and 2017. Anethum graveolens L. (dill), Raphanus sativus var. oleiformis Pers. (oilseed radish), Avena strigosa Schreb. (black oat), Carthamus tinctorius L. (safflower), Vicia sativa L. (vetch) and Phacelia tanacetifolia Benth. (phacelia) were sown in monocultures, as well as in mixtures with three or six species. Treatments with favorable establishment and above-average biomass yields tended to suppress weeds by showing lower weed dry matter and weed numbers. The highest weed control efficacy within the monocultures was reached in 2017 by black oat and oilseed radish with 72% and 83%, respectively. The mixture treatments reached a generally lower soil cover, aboveground dry matter and weed control efficacy (with an average of 57% in 2017). Even though mixtures were not as effective as the best performing single sown CCs, species combinations increased resilience against adverse weather conditions, an advantage to achieving efficient weed control over a long-term period. Therefore, species composition within mixtures is more relevant than the number of species included.

Modeling phosphorus reduction strategies from the international St. Clair-Detroit River system watershed

Nutrient loading from nonpoint sources has degraded water quality in large water bodies globally. The water quality of Lake Erie, the most productive of the Laurentian Great Lakes bordering the United States and Canada, is influenced by phosphorus loads from the Detroit River that drains an almost 19,000 km2 international watershed. We used the Soil and Water Assessment Tool (SWAT) to evaluate a range of management practices to potentially reduce total phosphorus (TP) and dissolved reactive phosphorus (DRP) loads. Scenarios included both single practices and bundles of multiple practices. Single practice scenarios included fertilizer rate reduction (Rate) and sub-surface placement (PL), filter strips (FL), grassed waterways, cover crops (CC), wetlands (WT), controlled drainage, and changes in tillage practices. Bundle scenarios included combinations of Rate, PL, FL, CC, and WT with three adoption strategies: application on all applicable areas, on 55% of randomly selected applicable areas, and on 55% of high phosphorus yielding applicable areas. Results showed that among the single practice scenarios, FL, WT, PL, CC, and Rate performed well in reducing both TP and DRP loss from agricultural dominated sub-watersheds. Over all, the CC, FL, WT bundle performed best, followed by the CC, PL, WT bundle, reducing the load up to 80% and 70%, respectively, with 100% implementation. However, targeting high phosphorus yielding areas performed nearly as well as 100% implementation. Results from this work suggest that there are potential pathways for phosphorus load reduction, but extensive implementation of multiple practices is required.

Uticaj jarih useva gajenih nakon ozimih međuuseva na stanje sabijenosti zemljišta

The aim of the paper was to determine the influence of cover crops (CC) and cultivated crops in the subsequent sowing period (maize, soybean and sudan grass) on the physical properties of the soil, and above all on the soil compaction.Research was carried out at the Rimski Šančevi experimental station. Type of soil - chernozem. The winter CC consisted of the combined intercrops: winter pea (Pisum sativum ssp. Arvense L.) + triticale ((×Triticosecale Wittm. ex A. Camus) (PT) and single-species CC winter pea (P)and control (without CC). Plowing of CC and control plots was carried out in the last week of May 2018, and the sowing of maize, soybean and sudan grass was carried out in early June. Soil compaction was analyzed on the basis of collected data on the resistance of cone penetration into the soil and the immediate moisture content of the soil. The penetration resistance of the cone into the soil was determined using an electric penetrologger Eijkelkamp Penetrologger. Measurement of the resistance was carried out to a depth of 80 cm and expressed in MPa. Based on the conducted research, the smallest percentage content of soil moisture at depths of up to 20 cm was determined for maize varieties (PT) of 10.5% vol.and the highest on the control plot (without CC) (25.7% vol.), as a consequence of the absence of the CC, but also the dense structure of Sudan grass and reduced evaporation from the production area. The lowest Cone index (CI) was measured on a plot also with sudan grass, on the soil preceded by the cultivation of the winter pea as cover crop ( 2,3), while the highest index (3,6) was measured in the soybean crop on variants (PT). The specific resistance to penetration of the cone was varied both on varieties of inter CC (PT), single CC (P) and control, as well as in different cultivated species in the subsequent sowing period. The highest value of the specific resistance in the depth 0-20 cm was found in soybean (PT) 2.76 MPa, and also increased compation in the same crop in the layer (20-40 cm). On the basis of the obtained values it can be concluded that maize least affects soil compaction, unlike soybean, while in relation to the cover crops it is determined that the winter pea has the least impact on soil compaction.

Contribution of Cover Crops to the Productivity of Maize‐Based Conservation Agriculture Systems in Zimbabwe

ABSTRACTResearch in Latin America has shown numerous benefits of rotations with cover crops under conservation agriculture (CA) to manage N and weeds; however, information from Zimbabwe is limited. The objective of the study was to investigate the benefits of rotating maize (Zea mays L.) with different leguminous and nonleguminous cover crops on maize yield, weed management, and decomposition rates of residues. A study was conducted at University of Zimbabwe (UZ), Domboshawa Training Centre (DTC), and two sites at Henderson Research Station (HRS) with contrasting soil types (clay and sand) from 2008 to 2014. Nine different cover crops were rotated with maize and compared with maize monocropping. During the 2012 to 2013 and 2013 to 2014 cropping seasons, a litter‐bag experiment was set within the experiment at UZ and DTC to investigate residue decomposition rates. Decreases in weed numbers of up to 94% were observed in maize–black sunnhemp (Crotalaria juncea L.) treatment at DTC. At UZ, maize after jack‐bean [Canavalia ensiformis (L.) DC.] (7823 kg ha−1) showed up to 61% more yield than continuous maize (4851 kg ha−1). Maize yields after fodder radish (Raphanus sativus L. var. oleiformis Pers.) were, in most cases, not significantly different from those of uniform maize. Decomposition rates were faster in leguminous residues, with velvet‐bean [Mucuna pruriens (L.) DC. var. utilis (Wall. ex Wight) Baker ex Burck] residues being generally the fastest and therefore not suitable for ground cover. Despite the positive effects of rotations, not a single cover crop was identified that provided all the benefits. There is need to characterize niches for specific cover crops within the farming system to assist farmers in their choices and spatial arrangements of cover crops on their farms.