Do organic farming practices improve soil physical properties?

Organic farming (OF) is a reemerging system that could address food security and adverse environmental footprints of conventional farming (CF). However, how OF affects the soil physical environment, an essential pillar for soil ecosystem service delivery, is not well understood. This paper (1) reviews published global literature up to 13 July 2023 regarding the impacts of OF on soil physical properties compared with CF and (2) underlines research needs. Literature indicates OF improves some soil physical properties relative to CF although studies on some properties were few. Specifically, OF increased wet aggregate stability, saturated hydraulic conductivity, and plant available water in 55% of studies. OF also increased mesoporosity (5–500 μm) and cumulative water infiltration. However, OF had mixed or no effects on soil compaction indicators (i.e. bulk density, penetration resistance). Not all studies reported both soil physical properties and soil organic C to assess how amendment-induced increase in soil organic C affected physical properties. Based on studies reporting both properties, physical properties such as wet aggregate stability were not significantly correlated (r = 0.12; p \u3e .10) with soil organic C. Variability in data and frequent tillage under OF likely obscured this relationship. Factors tended to affect OF impacts on physical properties in this order: amendment type \u3e duration \u3e others. Most OF studies (1) used animal manure amendments, (2) were long-term (\u3e10 years), and (3) were conducted in medium textured soils, highlighting the need for more comprehensive assessments of OF and soil physical properties under different management conditions. In general, OF improves some soil physical properties, which can contribute to OF sustainability

Soil properties limiting vegetation establishment along roadsides

Roadside vegetation provides a multitude of ecosystem services, including pollutant remediation, runoff reduction, wildlife habitat, and aesthetic scenery. Establishment of permanent vegetation along paved roads after construction can be challenging, particularly within 1 m of the pavement. Adverse soil conditions could be one of the leading factors limiting roadside vegetation growth. In this study, we assessed soil physical and chemical properties along a transect perpendicular to the road at six microtopographic positions (road edge, shoulder, side slope, ditch, backslope, and field edge) along two highway segments near Beaver Crossing and Sargent, NE. At the Beaver Crossing site, Na concentration was 81 times, exchangeable Na 66 times, and cone index (compaction parameter) six times higher at the road-edge position (closest to the paved road and with sparse vegetation) compared to positions with abundant vegetation (ditch or field edge). At the Sargent site, Na concentration was 111 times, exchangeable Na 213 times, and cone index up to two times higher at the road-edge position compared with ditch or field-edge positions. Likewise, electrical conductivity was higher and macroaggregation and water infiltration were lower at the road edge than at the ditch or field-edge positions. Soil properties improved with increasing distance from the road. Exchangeable Na percentage and cone index at the road-edge position exceeded threshold levels for the growth of sensitive plants. Thus, high Na concentration and increased compaction at the road edge appear to be the leading soil properties limiting vegetation establishment along Nebraska highways. Core Ideas • Roadside soil properties varied with microtopographic position along a transect perpendicular to paved road. • The road edge had highest compaction, Na, electrical conductivity, and pH. • The road edge had the lowest water infiltration and macroaggregation. • Roadside compaction, Na, and electrical conductivity exceeded threshold levels for plants. Includes supplementary material

Cover crop planting practices determine their performance in the U.S. Corn Belt

Cover crop growing periods in the western U.S. Corn Belt could be extended by planting earlier. We evaluated both pre-harvest broadcast interseeding and post-harvest drilling of the following cover crops: (a) cereal rye (Secale cereale L.) [RYE]; (b) a mix of rye + legumes + brassicas [MIX1], (c) a mix of rye + oat [Avena sativa L.] + legumes + brassicas (MIX2), (d) legumes [LEGU]) and (e) a no cover crop control. These were tested in continuous corn (Zea mays L.) [corn–corn] and soybean [Glycine max (L.) Merr.]–corn systems [soybean–corn] at three sites in Nebraska for their effect on cover crop productivity, soil nutrients, and subsequent corn performance. At the sites with wet fall weather, pre-harvest broadcasting increased cover crop biomass by 90%, to 1.29 Mg ha−1 for RYE and 0.87 Mg ha−1 for MIX1 in soybean–corn, and to 0.56 Mg ha−1 and 0.39 Mg ha−1 in corn–corn, respectively. At the drier site, post-harvest drilling increased biomass of RYE and MIX1 by 95% to 0.80 Mg ha−1 in soybean–corn. Biomass N uptake was highest in pre-harvest RYE and MIX1 at two sites in soybean–corn (35 kg ha−1). RYE and sometimes mixes reduced soil N, but effects on P, K, and soil organic C were inconsistent. In soybean–corn, corn yields decreased by 4% after RYE, and in corn–corn, by 4% after pre-harvest cover crops. Site-specific selection of cover crops and planting practices can increase their performance while minimizing impacts on corn

Cover crop productivity and subsequent soybean yield in the western Corn Belt

Cover crops (CC) in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] rotations may prevent N loss and provide other ecosystem services but CC productivity in the western Corn Belt is limited by the short growing season. Our objective was to assess CC treatment and planting practice effects on CC biomass, spring soil nitrate concentrations, and soybean yield at two rainfed sites in eastern and one irrigated site in south-central Nebraska over 4 yr. Cover crop treatments (cereal rye [Secale cereale L.] [RYE] and a mix of rye, legume, and brassica species [MIX]) were planted by broadcast interseeding into corn stands in September (pre-harvest broadcast) or drilling after corn harvest (post-harvest drilled) and terminated 2 wk before planting soybean. Cover crop biomass and N uptake varied between years, but generally at the eastern sites, pre-harvest broadcasting produced more biomass than post-harvest drilling (1.64 and 0.79 Mg ha−1, respectively) and had greater N uptake (37 and 24 kg ha−1, respectively). At the south-central site, post-harvest drilling produced more than pre-harvest broadcasting (1.44 and 1.20 Mg ha−1, respectively). RYE had more biomass than MIX (1.41 and 1.09 Mg ha−1, respectively), but the same N uptake. Soil nitrate reductions after CC were small. In 3 of 12 site-years, soybean yielded less after pre-harvest CC. Yield reductions were not correlated to CC biomass, but were likely due to greater weed pressure. High CC productivity is necessary for high N uptake, and requires site-specific selection of planting practice and CC treatments

Corn residue baling and grazing impacts on corn yield under irrigated conservation tillage systems

Crop residue grazing or baling is common in the western Corn Belt. However, its impacts on subsequent crop yields under different irrigation levels and tillage systems are unclear. We investigated the impacts of corn (Zea mays L.) residue baling and cattle grazing on soil compaction, water content, and corn yield under full and limited irrigated no-till in Nebraska during three years. In Years 2 and 3, an additional tillage treatment (strip till) was implemented to evaluate its effects on grain yield under the above treatments. Residue removal effects on compaction and water content did not vary with irrigation level. Grazing (3.68 animal units ha−1) minimally impacted compaction and soil profile water content compared to no removal. Baling increased cone index by 34–53% in the 0-to-12.5-cm depth and decreased water content by 6 cm compared to no removal. Residue removal effects on yield did not depend on irrigation. Residue removal impacts depended on tillage in Year 3 only. Full irrigation increased corn yields up to 11% compared to limited irrigation. Strip till increased yield by 11% compared to no-till in Year 2 only. Baling and grazing had no effect on corn yield in Year 1, but baling and grazing increased yield by 9% compared to no removal in Year 2, likely due to lower water content. In Year 3, grazing and baling increased yield by 9% under no-till but not strip till. Overall, grazing had minimal impacts while baling increased yield and compaction and decreased water content with few variations due to irrigation or tillage

Winter cover crop root biomass yield in corn and soybean systems

Cover crop (CC) roots are critical for soil ecosystem service delivery including soil stabilization, C and nutrient cycling, soil health improvement, and others. However, most CC studies only evaluate CC aboveground biomass yield, neglecting the belowground portion of the plant. The objectives of this study were to quantify the impacts of (a) CC planting (pre- and post-harvest) dates and (b) early (2–4 wk before main crop planting) and late (at main crop planting) CC termination with and without corn (Zea mays L.) residue removal on root biomass yield. We assessed the effects of CC planting or termination dates on root biomass yield for surface 10 cm of soil at four sites through sampling at CC termination and separating roots from soil with a hydropneumatic elutriation system. Pre-harvest CC planting had limited and variable impacts on root biomass yield compared with post-harvest planting. Corn residue removal had no impact on root biomass yield. However, CC termination date had effects at the Irrigated but not at the Rainfed site. At the Irrigated site, late-terminated CCs doubled root biomass yield in both years compared to early terminated and no CC. At this site, under late-terminated CCs, root biomass yield was 2.8 Mg ha–1 attributed to their higher aboveground biomass yield and later termination. At the Rainfed site, root biomass yield was 1.6 Mg ha-1. Overall, late termination of CCs can increase root biomass yield; however, early planting into the cash crop did not consistently increase root biomass yield under the conditions of this study

Increasing rye cover crop biomass production after corn residue removal to balance economics and soil health

Low or variable cover crop (CC) biomass production could limit CC benefits. Longer CC growing periods via late termination could increase CC benefits, especially under limited crop residue return. We studied whether early (2–3 wk before planting)- or late (at planting)-terminated winter rye (Secale cereale L.) CC maintains soil properties, crop yields, and farm income under 0%, 25%, 50%, 75%, and 100% corn (Zea mays L.) residue removal in rainfed and irrigated no-till in the U.S. Great Plains after 6 yr. Early-terminated CCs produced \u3c 1 Mg ha-1 of biomass while late-terminated CCs averaged 1.6 Mg ha-1 at the rainfed site and 3.0 Mg ha-1 at the irrigated site. At the rainfed site, CC termination date did not affect soils, but ≥ 75% residue removal reduced soil organic matter (OM) fraction concentrations and 100% reduced mean weight diameter of water-stable aggregates (MWD) in the 0–5 cm depth. At the irrigated site, late-terminated CC increased MWD by 0.22 mm and OM concentration by 5.1 g kg-1 compared with no CC. At the same site, 100% residue removal reduced microbial biomass, while ≥ 50% removal reduced OM concentration by 7.6 g kg-1, available water, and MWD by 0.75 mm relative to no removal. Cover crops only partially offset the adverse effects of residue removal if biomass production was 3 Mg ha-1 yr-1. Corn yield was generally unaffected. High residue removal rates offset CC-induced reduction in net income. Overall, late-terminated CC partially maintains soil health indicators following residue removal and minimally impacts crop yields and economics

Cover crops and soil health in rainfed and irrigated corn: What did we learn after 8 years?

Duration of cover crop (CC) management, CC biomass production, and other factors could impact how CC affects soil health. We studied the 8-year cumulative impacts of winter rye (Secale cereale L.) CC on soil physical, chemical, and biological properties in rainfed and irrigated no-till corn (Zea mays L.)-based systems in the western US Corn Belt. Average annual CC biomass production was 0.56 ± 0.51 Mg ha−1 at the rainfed site and 0.98 ± 0.95 Mg ha−1 at the irrigated site. After 8 years, CC improved particulate organic matter (POM) and mean weight diameter of waterstable aggregates (MWD) compared with no CC in the 0–5 cm soil depth at both sites. Cover crop increased total POM concentration by 2.8 mg g−1 at the rainfed site and by 13.4 mg g−1 at the irrigated site, while it increased MWD by 0.39 mm at the rainfed site and by 0.79 mm at the irrigated site. Also, CC increased soil C at a rate of 0.125 Mg ha−1 year−1 in the 0–5 cm depth but only at the rainfed site. Cover crop affected neither water infiltration nor available water but improved microbial biomass. Changes in other properties were site-dependent. Cover crop improved many soil properties after 8 years even though measurement taken after 4 years showed no significant effect of CC, which indicates CC slowly impacts properties in this environment. Low CC biomass production and high biomass input from corn-based systems may explain the slow soil response. In general, winter rye CC enhances near-surface soil properties in the long term