Trade-off between soil pH, bulk density and other soil physical properties under global no-tillage agriculture

Introduction: Saffron is one of the most important economic plants in the Khorasan province. Awareness of soil quality in agricultural lands is essential for the best management of lands and for obtaining maximum economic benefit. In general, plant growth is a function of environmental factors especially chemical and physical properties of soil (20). It has been demonstrated that there was a positive and high correlation between soil organic matter and saffron yield. Increasing the yield of saffron due to organic matter is probably due to soil nutrient, especially phosphorous and nitrogen and also improvement of soil physical quality (6, 28, 29). The yield of saffron in soils with high nitrogen as a result of vegetative growth is high (8). Shahandeh (6) found that most of the variation of saffron yield depends on soil properties. Due to the economic importance of saffron and the role of soil properties on saffron yield, this research was conducted to find the relationship between saffron yield and some soil physical and chemical properties, and to determine the contribution of soil properties that have the greatest impact on saffron yield in the Ghayenat area. Materials and Methods: This research was performed in 30 saffron fields (30 soil samples) of the Ghayenat area (longitude 59° 10΄ 10.37˝ - 59° 11΄ 38.41˝ and latitude 33° 43΄ 35.08˝ - 33΄ 44΄ 02.78˝), which is located in the Khrasan province of Iran. In this research, 21 soil properties were regarded as the total data set (TDS). Then the principal component analysis (PCA) was used to determine the most important soil properties affecting saffron yield as a minimum data set (MDS) and the stepwise regression to estimate saffron yield. To estimate the yield of saffron in stepwise regression method, saffron yield was considered as a dependent variable and soil physical and chemical properties were considered to be independent variables. Results and Discussion: According to the PCA method, among the 21 studied properties, 7 out of them including calcium, iron, zinc contents, sand, calcium carbonate equivalent percent, mean weight diameter of aggregates (MWD) and manganese (Mn) had the higher Eigenvalues. Therefore, the above properties were introduced as the most important soil properties in saffron fields. Calcium carbonate had the negative effect on the availability of micro-nutrients (26). Christensen et al. (15) found that by increasing the calcium carbonate in soil due to high pH and formation of insoluble components, the uptake of micro-nutrients is especially limited. The results of stepwise regression method (equation 1) showed that soil acidity (pH), zinc content, bulk density, MWD, iron content, salinity (EC), organic carbon and available potassium in soil were the most important properties that affect the yield of saffron, so that the determination coefficient (R2) of the regression model was high (Table 2) and it can explain 74% of the variation of saffron yield. Y = 6924.51 – 1187.31 pH – 89.65 EC + 71.6 Fe – 826.02 Zn + 471.55 OC, + 5490.96 K + 1353.56 BD + 752.82 MWD (1) where Y: saffron yield (kgha-1), pH: soil acidity, EC: electoral conductivity (dSm-1), Fe: iron concentration (mgkg-1), Zn: zinc concentration (mgkg-1), OC: organic carbon (%), K: soil potassium (%), BD: soil bulk density (Mgm-3), and MWD: mean weight diameter of aggregates (MM). Based on the absolute values of standard s in the regression model (Table 3), pH value and then after Zn concentration had the most effect on saffron yield. In general, responses of different plants to soil pH is varied, and saffron grows satisfactory in pH = 7.8 (5). Soil pH influences the uptake of soil nutrients by plants (15), so that this parameter had the most effect on saffron yield and by increasing the soil pH, the yield of saffron decreases. According to the regression model, Zn concentration was the second parameter in saffron yield. Zn has the important role in structure of plant enzymes (30). After these 2 parameters, Bd, MWD, Fe concentration, EC, Organic carbon and K concentration in soil had more effect on saffron yield (Table 3). Conclusion: According to both PCA and regression methods, the concentration of iron and zinc and MWD were determined as the important and effective soil properties on saffron yield in the Ghayenat area. In addition, soil pH in stepwise regression method and calcium carbonate in PCA method were determined as the effective properties on saffron yield. Therefore, it is suggested that the parameters of Zn, Fe, and MWD along with soil pH and calcium carbonate which were regarded individually in two methods, were considered as the most soil properties in saffron yield.

Conventional (CT) and no‐tillage (NT) effects on soil physical properties and bromide (Br) movement were studied at two locations in North Carolina. The soils were a Norfolk sandy loam (fine‐loamy, siliceous, thermic Typic Paleudult) at a North American eastern Coastal Plain location and a Pacolet sandy clay loam (clayey, kaolinitic, thermic Typic Kanhapludult) at a Piedmont location. Bulk density (Db), macroporosity (Mp), and saturated hydraulic conductivity (Ks) were measured in the plant row (R) and trafficked (T) or untrafficked (N) interrow positions. Simulated rain was applied at two intensities to 1−m2 plots after KBr was surface applied. The first simulated rain (30 min) consisted of a low (1.27 cm h−1) or a high (5.08 cm h−1) intensity applied 24 h after Br application. One week later, the high rainfall rate was repeated on all plots. Soil samples for Br determinations were taken 2 days after each rain simulation event to a depth of 40 cm and at the end of the growing season to 120 cm. Soil physical properties were affected by both tillage and position. Bulk density was greater for NT than for CT and in the T compared with R and N row positions. Mp was significantly greater in NT than CT at Coastal Plain location, but the results were opposite at the Piedmont location. Saturated hydraulic conductivity was highly variable ranging from 0.36 cm h−1 to 14.4 cm h−1 at the Coastal Plain location and from 0.06 cm h−1 to 7.12 cm h−1 at the Piedmont location. Saturated hydraulic conductivity at T position was about 100% lower than Ks at N and R positions, but the effect of tillage system was not significant on Ks. The surface 10 cm of soil contained the greatest Br concentration for both tillage systems. For the first and second sampling dates, greater Br movement occurred under NT vs. CT. However, no significant differences were observed in Br movement in the end of season sampling. Because of the coarser soil texture, greater Ks and Mp at the Coastal Plain location, Br moved, to a greater depth at this site than at the Piedmont site.

Soil quality as influenced by land use history of orchards in humid subtropics

Four soil conditioners, SAMMNS, CCT01, Mineral, and Tebeigai were selected for this study. The effects of the four conditioners on soil pH, bulk density, organic matter, available nutrients, texture, microaggregates, Cd available in soil, and Cd content in brown rice were investigated using field-controlled cadmium tests conducted in cadmium-contaminated paddy fields in Pingxiang. The results showed that compared to the control, soil conditioners could increase pH, bulk density, and cation exchange capacity in soil. SAMMNS and CCT01 soil conditioners increased the amount of silt and clay, but that of sand decreased, whereas the Mineral and Tebeigai soil conditioners decreased silt and clay, and sand increased. In addition to the CCT01 soil conditioner, the application of soil conditioners increased large-scale agglomerates and reduced small-scale microaggregates. The effects of soil conditioners on soil physical and chemical properties promoted the conversion of Cd from contaminated soil from high activity to low activity, which reduced available Cd content in soil (5.21%-34.78%) and Cd content in brown rice (51.39%-68.06%). Correlation analysis showed that Cd content in brown rice was significantly positively correlated with available Cd and available phosphorus in soil, whereas it was negatively correlated with pH and bulk density in soil. Considering the effects of soil and brown rice on cadmium reduction and physicochemical properties, Tebeigai soil conditioner exhibited the best repair effects, followed by SENMES and Mineral soil conditioner.

The intensity and frequency of inter‐row management in vineyards are highly diverse and depend on local environmental conditions and the wine grower's attitude and experience. Reasons for different management include water conservation, weed and pest control, biological activity promotion and soil fertility and biodiversity preservation. We studied different soil cover management in 16 paired vineyards located at eight sites in the Leithaberg and Carnuntum regions of eastern Austria. To this end, we compared inter‐rows with medium intensity (Periodically Mechanically Disturbed) and low intensity (Permanent Green Cover). We investigated the effects of these different management intensities on soil organic carbon, bulk density, saturated and unsaturated hydraulic conductivity, pore size distribution and percolation stability in the upper soil layer from 3 to 8 cm. Soil organic carbon and percolation stability were significantly higher and soil bulk density was significantly lower in vineyards with permanent green cover. No significant differences were observed for saturated hydraulic conductivity, pore size distribution and plant available water. This may be attributed to a minor effect as a result of the time lag of up to 2 years since the last tillage. Regression analysis to predict plant‐available water for local vineyard soils also showed that texture, total organic carbon and bulk density were suitable predictor variables. These results suggest that both investigated inter‐row management systems support a good soil structure for winegrowers. Organic carbon content and parameters interacting with organic carbon may still be improved with permanent vegetation cover systems; however, the positive effects on plant available water are limited.

Rice (Oryza sativa L.)-wheat (Triticum aestivum L.) a dominant cropping system in Punjab Region, Northwestern India, overtime is believed to have negative effect on the soil and water quality. The present study was conducted in an ongoing long-term experiment at the research farm of the School of Organic Farming, Punjab Agricultural University, Ludhiana, to compare the effect of different cropping systems on soil physico-chemical properties. Ten treatments (cropping systems) were laid in a Randomized Complete Block Design (RCBD). The treatments were rice-wheat (CS1), maize-wheat (CS2), basmati rice-wheat-cowpea green manure (CS3), maize-mustard-cowpea green manure (CS4), maize-potato-spring groundnut (CS5), maize-peas-spring groundnut (CS6), maize+ cowpea (fodder)-maize fodder-oats fodder-sathi maize fodder (CS7), sorghum multicut fodder-barseem fodder (CS8), maize (cobs/fodder)-potato-onion (CS9), and baby corn-potato-okra (CS10). Soil samples were collected from four soil depths (0-7.5, 7.5-15, 15-22.5, and 22.5-30 cm) under each cropping system and analyzed for particles size, soil pH, EC, soil organic carbon, aggregate associated carbon, bulk density, porosity, water stable aggregates, MWD, and penetration resistance. Significantly lower soil pH was reported in CS4 and CS8 compared to other cropping systems. Soil EC was significantly higher in CS5 and CS10 while lowest in CS4. Soil organic carbon (SOC), aggregate-associated carbon (AAC), and mean weight diameter (MWD) were significantly higher in CS7 and CS4. Soil bulk density (BD) and penetration resistance (PR) were significantly higher in CS1 and lowest in CS4. SOC was 19% higher in CS7 and BD was 16% lower in CS4 compared to CS1. Soil porosity and water-stable aggregates (WSA) were also found significantly higher in CS4 and CS7 whereas lowest in CS1. The increase in soil depths significantly increased the soil pH, BD and PR, whereas decreased the soil EC, SOC, AAC, porosity, MWD, and WSA. The cropping systems (CS4, CS7, CS8, CS6, CS5, CS3) with green manure/legume/fodder crops in rotation resulted in better physico-chemical properties through the addition of organic matter to the soil compared to cereal-cereal rotations.

Grazing cover crops (CCs) on no-till (NT) croplands in western and central Kansas could increase the profitability of crop production in these water-limited environments. However, little information exists about potential soil compaction associated with grazing CCs in these cropping systems. From 2019 to 2021, two studies investigated the effects of grazing CCs on soil bulk density and penetration resistance in NT cropping systems. At the Kansas State University HB Ranch near Brownell, KS, CCs grazed with yearling heifers were compared to ungrazed CCs and fallow under NT or occasional tillage (OT). In another study, CCs grazed with yearlings or cow-calf pairs were compared to ungrazed CCs across seven site-years on producer fields in western Kansas (Alexander and Hays) and central Kansas (Marquette 1 and 2). Soil bulk density and penetration resistance measurements were made at the time of subsequent grain crop planting following CCs. At Brownell, CC management, tillage, and their interaction had no significant effect (P > 0.05) on soil bulk density. Across years, bulk densities with fallow, ungrazed CCs, and grazed CCs were 1.11, 1.15, and 1.15 g/cm3at the 0- to 2-inch soil depth, respectively. Soil bulk densities with NT and OT were 1.14 and 1.14 g/cm3 at the 0- to 2-inch soil depth, respectively. Similarly, CC grazing had no significant effect on soil bulk density and penetration resistance across the seven on-farm sites-years. At the western Kansas locations, soil bulk density averaged 1.23 g/cm3 at the 0- to 2-inch soil depth with grazed or ungrazed CCs. At the central Kansas locations, soil bulk density averaged 1.31 and 1.36 g/cm3 at the 0- to 2-inch soil depth for grazed and ungrazed CCs, respectively. Bulk density measured at 2- to 6-inch depth was not different between grazed and ungrazed CC in either study. At Alexander, penetration resistance was 0.52 and 0.52 MPa with grazed and ungrazed CCs, respectively. Penetration resistance was 0.36 and 0.34 MPa with grazed and ungrazed CCs, respectively, at Marquette 1. Results showed that grazing CCs never increased soil bulk density or penetration resistance compared to ungrazed CCs. Based on these findings, grazing CCs on NT fields can be a strategy for producers to balance profitability and soil health.

Effect of tillage and crop rotations on pore size distribution and soil hydraulic conductivity in sandy clay loam soil of the Indian Himalayas

Crop rotation and residue management effects under no till on the soil quality of a Haplic Cambisol in Alice, Eastern Cape, South Africa

Progressive soil compaction is a disadvantage of intensive tillage. Compaction exerts a negative impact on the physical properties of soil and decreases crop performance. The adverse effects of soil compaction can be mitigated by replacing conventional tillage with simplified tillage techniques. Simplified tillage exerts a protective effect on soil, reduces production costs and preserves agricultural ecosystems. The aim of this study was to determine the influence of compaction and different tillage methods on the bulk density and moisture content of soil. The experimental factors were as follows: Soil compaction before sowing (non-compacted control treatment and experimental treatments where soil was compacted after the harvest of the preceding crop) and four different methods of seedbed preparation in a three-field rotation system (winter oilseed rape, winter wheat, spring barley). The influence of compaction on the bulk density and moisture content of soil varied across the rotated crops and their developmental stages. Soil compaction had no significant effect on the analyzed parameters in the cultivation of winter oilseed rape. In treatments sown with winter wheat, soil compaction resulted in significantly lower soil density and significantly higher soil moisture content. In plots sown with spring barley, soil compaction led to a significant increase in the values of both parameters. The average bulk density of soil after various tillage operations in the examined crop rotation system ranged from 1.49–1.69 g·m−3 (winter oilseed rape), 1.47–1.59 g·m−3 (winter wheat), 1.47–1.61 g·m−3 (spring barley). The bulk density and moisture content of soil were lowest after conventional tillage (control treatment) and higher after simplified tillage. Regardless of soil compaction, the greatest reduction in winter oilseed rape yields was noted in response to skimming, harrowing and the absence of pre-sowing plowing. Spring barley yields were higher in non-compacted treatments, whereas the reverse was observed in winter wheat. Chisel plowing and single plowing induced the greatest decrease in wheat yields relative to conventional tillage. Single plowing significantly decreased the grain yield of spring barley relative to the tillage system that involved skimming and fall plowing to a depth of 25.

There is a lack of understanding of how associations among soil properties and management-induced changes control the variability of greenhouse gas (GHG) emissions from soil. We performed a laboratory investigation to quantify relationships between GHG emissions and soil indicators in an irrigated agricultural field under standard tillage (ST) and a field recently converted (2 yr) to no-tillage (NT). Soil cores (15-cm depth) were incubated at 25 degrees C at field moisture content and 75% water holding capacity. Principal component analysis (PCA) identified that most of the variation of the measured soil properties was related to differences in soil C and N and soil water conditions under ST, but soil texture and bulk density under NT. This trend became more apparent after irrigation. However, principal component regression (PCR) suggested that soil physical properties or total C and N were less important in controlling GHG emissions across tillage systems. The CO2 flux was more strongly determined by microbial biomass under ST and inorganic N content under NT than soil physical properties. Similarly, N2O and CH4 fluxes were predominantly controlled by NO3- content and labile C and N availability in both ST and NT soils at field moisture content, and NH4+ content after irrigation. Our study indicates that the field-scale variability of GHG emissions is controlled primarily by biochemical parameters rather than physical parameters. Differences in the availability and type of C and N sources for microbial activity as affected by tillage and irrigation develop different levels and combinations of field-scale controls on GHG emissions.

Organic wastes have a positive impact on soil physical and chemical properties in the agroecosystems. However, its main effects on soil organic carbon (SOC) or total organic carbon, TOC (SOC and coal-C) contents as well as their effects on soil physico-chemical properties are still unclear. Two types of organic wastes (maize straw and manure) were utilized in dryland affected by mining activities to quantify their relative effect on soil physico-chemical properties. Regression analysis was used to assess the relationship between the soil physical properties, SOC, and TOC as well as their respective contributions to improving these properties. Treatments included control (CK), straw (S), low manure (LM), medium manure plus straw (S-MM), and high manure plus straw (S-HM). The results showed that SOC, soil bulk density, mean weight diameter (MWD), soil total porosity, soil penetration resistance, saturated hydraulic conductivity, and soil infiltration rate were strongly influenced by the application of organic wastes. A stronger linear relationship between SOC and the MWD, (R2 = 0.93, p < 0.05) compared to that between TOC and MWD indicated the important role of SOC in improving soil aggregation relative to the effect of TOC. According to the principal component analysis (PCA), the application of organic wastes had stronger effects on SOC contents and physical properties than TOC (SOC and coal-C). These findings advance our understanding of the actual effect of organic wastes on soil physical properties and SOC in dryland affected by mining activities and could inform fertilizer management decisions to improve soil properties.

Crambe grain yield and oil content affected by spatial variability in soil physical properties

Background: The application of composts to agricultural soil is a well-established practice with evidence showing multiple benefits within the field and beyond through changes in a number of soil functions. With soil health and function becoming increasingly important it is critical to understand the impact of soil management on function and changes in soil carbon, both within the root growth zone and, more importantly, within soil below the plough pan, an area of increasing interest.Methods: A long-term compost application trial was established in 2004 under continuous spring barley with 3 differing compost application rates and a unamended control treatment. Following establishment in 2004 all treatments, except the control, received 50 t ha-1 of municipal green compost, no amendments in 2005, low (35 t ha-1), medium (100 t ha-1), and high (200 t ha-1), applications in 2006 and 2007 before continuous 35 t ha-1 annual applications from 2008 to 2022. Plot structure is a randomised block design with soil being a sandy silt loam cultivated under minimum tillage practices. Intact soil cores were collected from both surface soils (~20mm) and subsoils (~300mm) for each plot in spring 2022 prior to compost application, cultivation, and sowing. Full water release data was collected including characterisation of the least limiting water range (LLWR), the available water beyond which mechanical impedance restricts root elongation (2.0 MPa). Additionally, soil resilience tests were performed to simulate trafficking with impacts on soil bulk density quantified and data on wet aggregate stability, visual evaluation of soil structure, and hydraulic conductivity were also collected.Results: Within surface soils, medium and high compost application rates increased hydraulic conductivity when compared to control plots, the low compost application rate decreased hydraulic conductivity when compared to unamended plots. Surprisingly, within subsoil, compost application was found to significantly impact hydraulic conductivity (P<0.04) with hydraulic conductivity shown to be higher within the medium rate compost application treatment. A significant difference in water stable aggregates (WSA) within surface soils was observed between treatments (P<0.01) and a significant difference in soil bulk density (BD) between treatments (P<0.01) with BD decreasing with increasing compost levels. No significant differences in sub soil bulk density were observed between treatments (P=0.131) however WSA was found to be significantly different in sub soils between treatments (P<0.01). Data on carbon, soil water release characteristics, and nutrient status will also be presented highlighting the long-term benefits of compost application.Conclusions: Results show that the surface application of compost under minimum tillage practice and the production of continuous spring barley can influence subsoil functions with wider ecosystem benefits.

Tillage-induced seasonal changes in soil physical properties affecting soil CO 2 evolution under intensive cropping