Reduced Soil Bulk Density Research Articles

Effects of loosening combined with straw incorporation into the upper subsoil on soil properties and crop yield in a three-year field experiment

Subsoil management needs to be integrated into the current tillage regimes in order to access additional resources of water and nutrients and sustain crop production. However, arable subsoil is often deficient in nutrients and carbon, and it is compacted, affecting root growth and yield. In this study, crop yield and soil responses to loosening of the upper subsoil, without and with straw injection below the plough layer (25–34 cm), were studied during three crop cycles (2016–2018) in a field experiment near Uppsala, Sweden. Responses to straw injection after loosening were studied after single and triple consecutive applications of 24–30 Mg ha−1 during 2015–2017 to spring-sown barley and oats. Subsoil loosening combined with one-time or repeated straw addition (LS treatments) significantly reduced soil bulk density (BD) and increased porosity, soil organic carbon (SOC) and total nitrogen (N) compared with loosening (L) alone (one-time or repeated annually) and the control. In treatment L, the soil re-compacted over time to a similar level as in the control.Field inspections indicated higher abundance of earthworms and biopores in and close to straw incorporation strips. Aggregates readily crumbled/fragmented by hand and casts (fine crumbs) were frequently observed in earthworm burrows. The treatment LS improved soil properties (SOC and porosity) and water holding capacity, but had no significant influence on crop yield compared with the control.Crop yield in all treatments was 6.5–6.8 Mg ha−1 in 2017 and 3.8–4.0 Mg ha−1 in 2018, and differences were non-significant. Absence of yield effect due to treatments could be possibly due to other confounding factors buffering expression of treatment effects on yield. Lower relative chlorophyll content in leaves in the loosening with straw treatment during early growth stages, did not affect final crop yield. Subsoil loosening performed three times gave no further improvement in soil properties and grain yield compared with one-time loosening. There was no difference in yield between repeated subsoil loosening + straw and one-time treatment. It will be interesting to study the long-term effects of deep straw injection and evaluate its impact under other soil and weather conditions.

Long-Term Effects of Biochar Application With Reduced Chemical Fertilizer on Paddy Soil Properties and japonica Rice Production System

To clarify the effects of co-application of rice-straw biochar and different chemical fertilizer doses on paddy soil properties and japonica rice production in Northeast China, a located-field experiment was adopted for 5 years. The treatments included fertilization (F, no biochar, control) and rice-straw biochar (7.5 t ha−1) combined with different chemical fertilizer doses (100, 80, and 60% that of F) set as CF, CF1, and CF2, respectively. The results showed that the co-application of biochar and chemical fertilizers after 5 years reduced soil bulk density, increased soil total and capillary porosity, changed the soil solid–liquid–gas ratio (increased the liquid and air ratios and decreased the solid ratio), and increased soil macroaggregates (>0.25 mm) and aggregate stability, which enhanced the soil’s physical properties. Furthermore, the co-application improved soil pH and soil enzyme activity (urease, sucrase, and catalase) and had a significant effect on promoting SOM. The soil total N, P, and K of CF and CF1, were 23.48, %, 47.28%, and 26.59% and 9.47%, 43.98%, and 27.87% higher than those of the control, respectively. The soil available nutrients (N, P, and K) increased in the co-application treatment, shown as the nitrogen was promoted higher in the early growth of rice, while phosphorus and potassium were exhibited greater in the late growth. With the soil amendment, the co-application increased the rice plant height and dry matter accumulation, and the CF and CF1 increased yields by 5.78 and 2.41%, respectively, by increasing the rice effective panicles, grains per panicle, and seed-setting rate. The co-application of biochar and chemical fertilizers could significantly amend soil properties and reduce chemical fertilizer use to ensure rice–grain output, which has an important significance for enhancing sustainable soil and crop productivity.

Ecological resilience of physical plant-soil feedback to chronic deer herbivory: Slow, partial, but functional recovery.

Ecological resilience to ungulate overbrowsing is an important issue in forest ecosystems. After chronic herbivory, the recovery rate of understory vegetation and its related functions can be slow even with decreasing grazing intensity; thus, detecting elasticity during alternative successional trajectories is fundamental to understanding state perturbations. In this context, we focused on physical plant-soil feedback (functional interactions between plant growth and soil physical conditions) and evaluated elasticity and recovery processes according to deer density. The effects of 40 years of chronic herbivory by sika deer (average density 14.7 individuals km-2 ) on the recovery of understory plant communities and associated changes in soil physical properties in headwater catchments were assessed. Using 8 years of catchment-wide exclusion (fenced) and reduction (only culled; average 4.3 individuals km-2 ) treatments, plot sampling was conducted in 2010 (before treatment) and 2018 (after treatment). The recovery of vegetation and soil physical properties were evaluated, and functional plant-soil relationships and spatial variability were assessed to detect recovery processes during alternative successional trajectory. Woody species increased only under the exclusion treatment and the average soil bulk density was lower than that under reduction treatments. Soil bulk density was negatively correlated with root biomass in the fenced catchment, and root biomass was positively associated with woody species richness. Reduced soil bulk density (~0.5g cm-3 ) was observed with greater root biomass and woody species richness on upper hillslopes in the deer-excluded catchment where plant coverage was minimal. Successional failure under the reduction treatment suggested slow recovery with a depressed threshold according to deer density, indicating a clockwise hysteretic response to deer density. Unlike plant coverage during the earlier period of overbrowsing, woody species root development led the recovery of functional physical plant-soil feedback; however, this was probably limited by the higher soil erosion rate in riparian areas and an under-developed herb layer. Our results highlight an alternative recovery trajectory of physical plant-soil feedback driven by an alternative plant element (woody roots) to recovery trajectory with increasing plant cover. However, riparian erosion and herb layer would still suppress recovery. Therefore, recovery might be slower at the landscape scale.

Effects of the application of different improved materials on reclaimed soil structure and maize yield of Hollow Village in Loess Area.

In order to solve the soil problem of poor structure and low fertility after the abandoned homestead reclamation of Hollow Village in Loess Area and to improve the quality of the reclaimed soil in Hollow Village, a five-year field experiment was conducted here. In this experiment, the following seven treatments were applied: no modified material (CK), maturing agent (TM), fly ash (TF), organic fertilizer (TO), maturing agent + fly ash (TMF), maturing agent + organic fertilizer (TMO) and fly ash + organic fertilizer (TFO), and the effects of different improved materials on soil properties and crop yield were studied. The results showed that: soil organic matter (SOM) and total nitrogen contents increased significantly after the application of different improved materials, which promoted the cementation and aggregation of water-stable microaggregates (< 0.25 mm), and the water-stable macroaggregates showed an increasing trend. In the 0–0.15 m soil layer, the proportion of water-stable macroaggregates under TM, TF, TO, TMF, TMO, and TFO treatment increased by 328.2%, 130.0%, 87.8%, 81.1%, 36.7%, and 12.2% compared with CK, respectively. Meanwhile, TF, TO, TMF, TMO, TFO treatments significantly increased the mean weight diameter (MWD) and geometric mean diameter (GMD) values, reduced soil bulk density, the stable aggregate index (ELT) and fractal dimension (D) values (P < 0.05), and the stability of soil structure and the capacity of soil moisture retention has been significantly improved. The SOM content had a significant positive correlation with MWD, GMD, and > 2 mm water-stable aggregates and a significant negative correlation with the ELT, D, and water-stable microaggregates. In particular, the organic–inorganic coupling treatment of TFO showed the highest SOM content, soil moisture content, water-stable macroaggregates and maize yield, which was the most appropriate amendment for improving the reclaimed soil structure and fertility of Hollow Village in Loess Area.

Sensor-based Irrigation Scheduling, Soil Physical Properties and Wheat Productivity under Different Organic Amendments

ABSTRACT Sensor-based irrigation scheduling in field crops like wheat for achieving optimum yield with minimum use of water needs investigation under different amendment practices. The present study was thus conducted to investigate the effect of four irrigation regimes i.e., soil moisture indicator (red level of indication, SMI), tensiometer (35 k Pa), IW/Pan-E 0.9, and IW/Pan-E 0.6 in main plots and four organic amendments i.e., farm yard manure (FYM), rice straw mulch, hydrogel and without amendments in subplots on soil physical properties and wheat productivity. The field experiment was laid out in split plot design with three replications during rabi 2020–21 at Research Farm, Department of Soil Science, PAU, Ludhiana. The use of SMI shows promising results in respect of scheduling irrigation in wheat as similar biological yield with same amount of water was achieved as that observed for recommended practice i.e., IW/PAN-E = 0.9. The results further indicate that the use of amendments, particularly FYM, leads to reduction in soil bulk density by 4%, while the soil moisture content at field capacity and water-holding capacity by 14% and 9.3%. It is, thus, concluded that scheduling irrigation based on SMI along with FYM in wheat is a suitable practice for northwest India.

Effects of Cotton Stalk Returning on Soil Enzyme Activity and Bacterial Community Structure Diversity in Cotton Field with Long-term Saline Water Irrigation

Long-term saline water irrigation will increase soil salinity, adversely affect soil physical and chemical properties, and change the diversity of soil bacteria. Straw returning can improve the soil microenvironment and subsequently affect soil enzyme activity and bacterial community structure diversity. This experiment used two types of irrigation water salinity:fresh water (FW, 0.35 dS·m-1) and saline water (SW, 8.04 dS·m-1). Under each irrigation water salinity, the amount of cotton straw applied was 0 and 6000 kg·hm-2 (represented by FWST and SWST, respectively). The results showed that:compared with those under fresh water irrigation, saline water irrigation significantly increased the soil salt, bulk density, total carbon, and available phosphorus but significantly decreased available potassium content. Under saline water irrigation, straw returning significantly increased the soil total carbon, total nitrogen, available potassium, and available phosphorus but reduced soil bulk density. Compared with those under fresh water irrigation, soil sucrase, alkaline phosphatase, and catalase activities under saline water irrigation decreased by 57.24%, 35.15%, and 3.91%, respectively, whereas urease activity increased by 26.73%. However, straw returning significantly increased sucrase, alkaline phosphatase, and catalase activities but decreased urease activity. Saline water irrigation decreased the relative abundance of Acidobacteriota, Actinobacteriota, Bacteroidota, Verrucomicrobiota, and Firmicutes and increased the abundance of Gemmatimonadota and Myxococcota. Under saline water irrigation, straw returning significantly increased the relative abundance of Actinobacteriota, Bacteroidetes, Firmicutes, Crenarchaeota, Sphingomonas, Dongia, and Steroidobacter. NMDS results also showed that saline water irrigation and straw returning changed the bacterial community structure. In conclusion, straw returning can improve soil nutrient content, reduce soil bulk density and salinity, and then change soil enzyme activity and bacterial community structure diversity. The change in soil bacterial community composition was mainly affected by soil salinity and bulk density. Therefore, straw returning can improve soil fertility and help maintain the health of soil ecosystem. This study revealed a relationship between soil enzyme activities and bacterial communities, which provides a theoretical basis and mechanism for applying cotton stalk to regulate the soil enzyme and micro-ecological environment.

Restoration of degraded sodic soils through silvipastoral systems in the Indo‐Gangetic Plains

AbstractExcessive salts in degraded sodic soils aggravate the bio‐physicochemical properties of soils that need to be remediated and restored in a judicious way. The present study envisages smothering harmful effects of sodic soils and maintaining soil fertility through need‐based silvipastoral systems. We report on a three‐times replicated field experiment with 13 treatments comprised of three agroforestry tree species Acacia nilotica, Casuarina equisetifolia, and Eucalyptus tereticornis planted during 2005 on highly sodic soil of pH 10.6 and exchangeable sodium percentage (ESP) of 89 in the Indo‐Gangetic Plains. Fodder grass species viz. Chloris gayana, Panicum maximum, and Pennisetum purpureum were planted under each of the 10‐year‐old tree species. The maximum biomass production of understory grasses was recorded from A nilotica + C. gayana silvipastoral system while the highest nutritive value in terms of N. P, K, and crude protein content (%) was recorded in A. nilotica + P. purpureum. A strong correlation between photosynthetically active radiation (PAR) and understory grasses was observed. Significantly higher tree growth and biomass yield were recorded under silvipastoral systems over silvicultural system. A significant reduction in soil bulk density and increase in soil porosity, infiltration rate, and water holding capacity (WHC) were recorded in silvipastoral systems over silviculture and control due to reduced sodicity, addition of leaf litter, increase in microbial activities due to tree and grassroots, better plant growth, and fine root decay. Reduction in soil pH, exchangeable sodium percent (ESP), and increase in soil organic carbon were more pronounced under silvipastoral systems over the silviculture. The highest reduction in these parameters was recorded under the A. nilotica + C. gayana silvipastoral system. Similarly, soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP), and dehydrogenase activities were higher under silvipastoral systems over the silvicultural system The highest MBC was recorded in C. equisetifolia + C. gayana which was 302.8% higher than the control. However, highest MBN and dehydrogenase activities were recorded under A. nilotica + C. gayana silvipastoral system. Hence, on the basis of total biomass yield and improvement in soil bio‐physicochemical properties A. nilotica + C. gayana silvipastoral system could be a highly ameliorative and productive system for the restoration of degraded sodic soils.

Effect of Long-Term Biodegradable Film Mulch on Soil Physicochemical and Microbial Properties.

Biodegradable mulches have become the focus of attention, as pollution caused by leftover plastic mulch material becomes increasingly severe. However, the impact of biodegradable mulches to the soil needs to be further investigated. An experiment was conducted to evaluate the impact of no-mulch, biodegradable film mulch (BM) and polyethylene film mulch (PM) on the soil’s physical, chemical and biological properties after six years (2013–2019) of mulching in garlic growing season in a garlic-maize rotation. Results showed that the soil bulk density of the 10–20 cm soil layer under BM decreased by 12.09–17.17% compared with that under PM. The soil total nitrogen content increased significantly by 14.75–28.37%, and the soil available phosphorus and potassium content increased by 64.20% and 108.82%, respectively. In addition, BM increased the soil’s microbial, soil urease, and soil catalase activities compared with those for PM. To sum up, BM can reduce soil bulk density, and long-term use of BM does not cause a decrease in soil nutrient content and microbial activity. On the contrary, it can improve soil quality. This study helps accumulate data for the environmental safety evaluation of BM and provides theoretical and technical support for the large-scale promotion of biodegradable mulches.

Impact of Subsoiling on Cultivated Horizon Construction and Grain Yield of Winter Wheat in the North China Plain

In order to explore the effects of subsoiling tillage measures on the construction of soil cultivated horizon and the yield and water use efficiency of winter wheat in the North China Plain, three tillage methods, including no tillage (PZ), rotary tillage (PR), and subsoiling (PS), combined with straw returning measures were implemented in the winter wheat season in Xinxiang, Henan Province from 2016 to 2018. The effects of tillage measures on the improvement of cultivated land quality and the water saving and yield increase of winter wheat were investigated. The results showed that compared with no-tillage treatment, subsoiling significantly reduced soil bulk density by 8.88% and increased soil porosity by 13.04% in 20–40 cm soil layer; significantly reduced soil compaction by 56.96% in 0–40 cm soil layer; subsoiling combined with straw returning significantly increased soil organic carbon content in plough layer of winter wheat, whereas rotary tillage decreased soil organic carbon content. Subsoiling is more conducive to soil moisture movement to the deep layer after irrigation or rainfall, and the water consumption of subsoiling is the largest in the whole growth period of winter wheat. Subsoiling could better coordinate the relationship between water consumption and yield, which increased yield by 34.48–38.10% and water use efficiency by 19.57–21.96% compared with no-tillage treatment, respectively. Therefore, subsoiling before sowing combined with straw returning was beneficial to the reasonable construction of soil cultivated horizon, and significantly improved the yield and water use efficiency of winter wheat under the climatic conditions in the North China Plain.

Potentials of straw return and potassium supply on maize (Zea mays L.) photosynthesis, dry matter accumulation and yield

Maize (Zea mays L.) is considered one of the most important grains in the world. Straw return has the effect of reducing soil bulk density and increasing soil porosity. Straw returning and potassium fertilizer can supplement soil potassium content. The improvement of soil structure and the optimization of soil nutrient levels provide a good environment for high yield and high efficiency of maize. Therefore, three field experiments were carried out over a three-year period (2018–2020) to study the effects of straw returning on photosynthesis, dry matter accumulation and yield of maize 'Xianyu 335' under two different fertilization methods and four potassium application levels. The results showed that straw returning and potassium application had significant effects on the above indicators. The above indicators were significantly improved by deep tillage straw returning compared with no tillage straw returning. Increasing potassium supply can promote the effect of straw returning. The photosynthesis, dry matter accumulation and yield parameters of maize treated with straw returning and deep tillage combined with 60 kg/hm2 potassium fertilizer (SFK60) reached the highest in the three harvest seasons. The corn planting profit of SFK45 treatment is the highest, which is $1868.92 per ha. Therefore, SFK45 is an effective way to ensure stable and high yield of corn and maximize farmers' income.

Effects of Plant Mulch and Vine Care on the Growth and Yield of Cucumber (Cucumis sativus L.)

Field experiments were conducted in the 2015 cropping seasons on farmer’s farm, Abeokuta, Ogun State, Nigeria to study the effects of plant mulch and vine care on soil properties, leaf nutrient content, growth, and yield cucumber (Cucumis sativus L.). Plant mulch was applied as zero mulch (0 t ha-1), Tithonia diversifolia (10 t ha-1), Chromolaena odorata (10 t ha-1 ) and vine care as no stake staked and trellised. It was a 3 x 3 factorial experiment arranged in a randomized complete block design with three replicates. Pre-experiment soil samples and soils from each plot at the end of the experiment were collected for soil physical and chemical analysis, plant growth and yield parameters were measured, and leaf nutrient analysis was carried out. Both Tithonia and Chromolaena mulches significantly (P ≤ 0.05) reduced soil bulk density and temperature and increased soil moisture content and total porosity. They also significantly (P .≤ 0.05) increased soil OC, pH, N, P, K, Ca, Mg, leaf P, K, Ca and Mg concentrations, growth, and cucumber yield compared with the control. The application of vine care further enhanced the performance of cucumbers. Staked and trellised methods performed better than the control in most growth and yield parameters examined. Cucumber fruit yield was increased by plant mulch (Tithonia 84.3%, Chromolaena 39.7%) and vine care (trellised 54.2%, staked 26.2%) compared with control. Application of Tithonia mulch and trellising cucumber vines was found suitable for cucumber production

Assessing the synergistic impacts of poultry manure and biochar on nutrient-depleted sand and sandy loam soil properties and sweet potato growth and yield

Summary Poultry manure (PM) has been shown to boost crop productivity. However, little is known about its favorable interactions with wood biochar (B) on sweet potato (Ipomoea batatas L.) growth and yield, and soil qualities. Hence, a 2-year field trial was conducted in the southwest Nigeria at two locations (Owo – site A and Obasooto – site B) to co-apply PM and wood B as soil amendments to boost sweet potato productivity and soil quality. The experiment consisted of a 3 × 4 factorial layout with three replications. PM and B significantly reduced soil bulk density and improved porosity and moisture content with their rate of application when compared to the control. As PM and B applications increased from 0 to 10.0 t ha−1 and 0 to 30.0 t ha−1, respectively, soil chemical properties and sweet potato growth and tuber yield increased. Co-application of 10.0 t ha−1 PM and 30.0 t ha−1 B increased tuber yield by 220% compared to treatments without PM or B. Significant synergistic interactions between PM and B were observed for all parameters. In comparison with other treatments, co-applying PM and B to sweet potato soils is a viable sustainable option for increasing sweet potato productivity and soil sustainability.

Impact of Natural Rubber Tire Waste Charcoal on Selected Soil Physical Characteristics of Tea Growing Soils

The present study assessed the impact of application of natural rubber tire waste charcoal (NRTWC) on selected physical characteristics of tea cultivated soils which belongs to Red Yellow Podzolic great soil group. Natural rubber tire waste charcoal was applied as a soil amendment at different rates (0%, 1%, 1.6%, 2.2% and 2.8% w/w). Physical attributes of soil; bulk density, particle density, porosity, texture and aggregate stability were assessed at 10 and 20 weeks after application of NRTWC. Natural rubber tire waste charcoal significantly improved physical characteristics of soil by reducing soil bulk density, and increasing particle density, porosity and aggregate stability. Natural rubber tire waste charcoal treated soils showed significantly (p ≤ 0.05) lower bulk densities for the application rates of 2.2% and 2.8% (1.21 and 1.17 gcm-3 respectively) compared to the control (1.39 gcm-3) at 10 weeks after application. Significantly (p ≤ 0.05) lower particle density was observed for the application rate of 2.8% (2.52 gcm-3) than the control at 20 weeks after application. The increased porosity with time might be attributed to the increased of soil organic matter content with the application of NRTWC. The highest porosity change was observed at 1 % treatment (from 44.9% to 48.8%) and the lowest was at 2.8% (from 49.4% to 56.3%). Despite no significant (p ≥ 0.05) difference was reported in particle size distribution in soil treated with NRTWC, there was a noticeable decreased in sand percentage and increased in either silt or clay percentages at 20 weeks after application. Soil aggregate stability was found to be significantly increased (p ≤ 0.05) in all treatments at 10 and 20 weeks after NRTWC application compared to the control. However, further investigations are needed before recommending the addition of NRTWC as an amendment to tea growing soils.

Effect of Smashing Ridge Tillage Depth on Soil Water, Salinity, and Yield in Saline Cotton Fields in South Xinjiang, China

To explore the potential of smashing ridge tillage irrigation, it is necessary to investigate how smashing ridge tillage technology with mulched drip irrigation affects soil water, salinity, and cotton yield in saline fields. We conducted a two-year (2020–2021) field experiment to study the effects of different smashing ridge tillage depths on soil bulk density, moisture, salinity, dry matter production, yield, and its constituents (effective bolls, 100-bell weight). There were three smashing ridge tillage depths: A (20 cm), B (40 cm), and C (60 cm), with traditional tillage as the CT. The results showed that all of the smashing ridge tillage could reduce soil bulk density, improve the utilization and uptake of deep soil water during the rapid growth period, and reduce the soil salt content. Compared with the CT treatment, the average soil bulk density of the 0–60 cm soil layer in treatments A, B, and C in 2020 and 2021 decreased by 3.05%, 5.87%, 10.09%, and 1.65%, 4.48%, and 8.49%, respectively. The average soil water content in the 0–120 cm soil layer at the flowering and boll stage decreased by 3.68%, 6.28%, 9.04%, and 3.59%, 6.52%, and 9.98%, respectively; the soil salt content in the 0–120 cm soil layer at the boll opening stage decreased by 4.21%, 6.75%, 11.95%, and 5.47%, 24.25%, and 54.13%, respectively. Cotton dry matter production and yield tended to increase with an increasing depth of smash ridge tillage. Treatment C obtained the maximum dry matter production, seed cotton yield, effective bolls, and 100-boll weight. The dry matter production at the boll opening stage was significantly increased by 17.16% and 15.91%, and the yield was significantly increased by 65.24% and 84.14% in treatments C in 2020 and 2021, respectively, compared to CT. The smashing ridge tillage of 60 cm can optimize the structure of the soil tillage layer and also reduce soil salinity and increase yield, which is the suitable depth of smashing ridge tillage for saline cotton fields in the south of Xinjiang. The findings of the study can provide some theoretical basis and practical experience for the improvement of saline soils and sustainable agricultural development in South Xinjiang, China.

Optimal biochar application rates for mitigating global warming and increasing rice yield in a subtropical paddy field

Summary Application of biochar to rice has shown to elicit positive environmental and agricultural impacts due to its physicochemical properties. However, the relationship between greenhouse gas (GHG) emissions, rice yield, and soil nutrient status under biochar amendment remains unclear. In this study, rice yield and methane (CH4) and nitrous oxide (N2O) emissions were quantified in response to biochar application rate (0, 10, 20, and 40 t ha−1) to early and late subtropical rice cropping systems. We found that application of 10 t of biochar ha−1 to early rice reduced average CH4 emission fluxes, while all biochar application rates diminished average emissions in late rice paddy. Total global warming potential (GWP) and GHG intensity (GHGI) were inherently greater in late rice than early rice cropping. In early rice, GWP and GHGI were found to be similar between soil control, 10 and 20 t of biochar ha−1 treatments, although the largest occurred in the 40 t of biochar ha−1 treatment, whereas in late rice cropping, they were not affected by biochar application rates. Compared to the nil-biochar application, biochar application at varied rates did not affect rice yield. However, compared to 10 t biochar ha−1, increasing biochar application rate to 40 t ha−1 significantly decreased total rice yield (sum of early and late cropping). Generally, application of biochar increased soil salinity and total Fe and Fe2+ content while reducing soil bulk density. Temporal effects of biochar application were noted on CH4 emission flux, soil temperature, and soil Fe2+ and Fe3+ in early rice; and soil temperature, salinity, NH4+-N, NO3−-N, and soil Fe2+ and Fe3+ in late rice. This study confirms that the application of biochar at the lower rate of 10 t ha−1 is optimal for maintaining rice yield while reducing GHG emissions. Moreover, the study demonstrates the potential benefit of biochar in sustainable subtropical rice production.

Soil carbon sequestration and soil quality change between no-tillage and conventional tillage soil management after 3 and 11 years of organic farming

ABSTRACT The aim of this study was to evaluate the long-term effect of no-tillage systems in organic farming on soil carbon sequestration and soil quality, which is associated with nutrient availability. The experiment was conducted on a low-input organic farm since 2009, using a randomized complete block design with four replications. Two treatments, conventional tillage (CT) and no-tillage (NT), were tested. Soil samples were obtained after crops were harvested in 2012 and 2020 from four different soil depth layers between 0‒30 cm, and the physical and chemical properties of soil samples were measured. Data were analyzed using ANOVA with Tukey tests (α = 0.05), while the correlation was analyzed based on Pearson correlation. At 0–2.5 cm and 2.5–7.5 cm depths, soil bulk density (BD) in the NT treatment was 30% and 8% lower, respectively, in 2012, and 25% and 14% lower, respectively, in 2020 compared with the CT treatment. The NT treatment could enhance the soil organic carbon (SOC) better than CT treatment at the same depth, sequestering a greater amount of carbon in the soil. Compared with the CT treatment, SOC concentration in the NT treatment was 76% and 12% higher, respectively, in 2012, and 103% and 38% higher, respectively, in 2020. In 2012, the SOC stock showed a significant difference between NT and CT treatments only at the 0–2.5 cm soil depth, with the value being 24% higher in the NT treatment than in the CT treatment. However, in 2020, the SOC stock was 50% and 19% higher in the NT treatment than in the CT treatment at 0–2.5 cm and 2.5–7.5 cm depths, respectively. The SOC also could significantly expand cation exchange capacity (CEC) and the availability of some nutrients in the soil. However, the relationship between was weak in 2020. Moreover, the NT treatment showed better progression of humification than CT. Finally, long-term NT systems in low-input organic farming could reduce soil bulk density and enhance soil carbon sequestration and soil quality. However, this system must be complemented with the conventional approach to maintain nutrient balance for long-term management.

The effect of organic waste application on some soil physical properties, growth and yield of red rice between conventional and aerobic irrigation system on raised-beds

The objective of this study was to evaluate the effect of organic waste application on some soil physical properties, growth and yield of red rice between conventional and aerobic irrigation systems on permanent raised-beds. The experiment was carried out in May to August 2020, under Split Plot design with two factors namely techniques of rice cultivation (conventional, T1; aerobic irrigation system, T2) as main plots, and organic wastes (L0=without organic waste, L1=rice husk, L2=rice husk ash, L3=rice husk ash and cattle manure) as the subplots. Results indicated that both treatment factors affected some physical properties of the soil, growth, and yield of red rice. Some variables showed significant interaction namely soil bulk density, red-rice height, leaf number and dry straw weight. Changing rice cultivation technique from conventional to aerobic irrigation system significantly reduced soil bulk density, especially under application of rice husk ash together with cattle manure or without cattle manure, resulting in the highest red rice grain yield of 37.78 g/clump whereas under conventional without organic wastes, grain yield was only 21.27 g/clump. On average, changing from conventional technique to aerobic irrigation system could increase red rice grain yield by 40.13%.

Soil carbon stocks and water stable aggregates under annual and perennial biofuel crops in central Ohio

Biofuels have the potential to mitigate global warming by partially replacing fossil fuels. Long-term cultivation of bioenergy crops may affect soil quality and C exchange between the soil-plant-atmosphere continuum depending upon crop type and duration of cultivation. Thus, studies are needed to compare the impact different bioenergy crops have on soil organic carbon (SOC) stocks to estimate the net C mitigation potential of these crops. This study reports on changes in soil properties and C stocks after eight years of annual no-till (NT) corn (Zea mays L.), sorghum (Sorghum bicolor L.), perennial switchgrass (Panicum virgatum L.), miscanthus (Miscanthus x giganteus), and polyculture prairie cultivation in central Ohio. Perennial biofuel crops (PBCs) improved soil health by reducing soil bulk density, increasing soil porosity, and improving soil aggregate stability compared to those under annual bioenergy crops (ABCs). Changes were most prominent in the surface 0–10 cm soil layer. Bulk density decreased by 14.4% and 12.8% under PBCs and 6.0% and 5.7% under ABCs in the 0–10 cm and 10–20 cm depths, respectively. Water stable aggregate values in the PBC systems were 29.6% (0–10 cm) and 23.0% (10–20 cm) greater than those in the ABC systems with maximum and the minimum values observed under miscanthus (95.1%) and corn (70.2%). PBC systems retained 71% of overall aggregates within the > 4.75 mm size fraction after wet sieving and 2% in the < 0.25 mm size fraction, compared to ABCs retaining 20% and 28% of total aggregates within these two aggregate size fractions, respectively. C and N accumulation were greater in macroaggregates (>0.25 mm) compared to microaggregates (<0.25 mm). The SOC stock within the first eight years of the study decreased by 8.25 Mg C ha−1 (annual rate of −1.03 Mg C ha−1 y−1) for the ABC systems. In contrast, the SOC stock under PBCs for the first eight years increased by 7.94 Mg C ha−1 at an annual rate of 0.99 Mg C ha−1 y−1. These data indicate that PBCs enhanced SOC stocks and provided the dual benefit of increasing SOC stock and improving soil properties. The rate and cumulative amount of SOC sequestration were the highest under miscanthus and the least under sorghum. However, more information is needed on the C life-cycle of biofuel crops and profile C changes to evaluate the net C mitigation potential.

Effects of subsoiling rotational patterns with residue return systems on soil properties, water use and maize yield on the semiarid Loess Plateau

In recent years, conservation rotational tillage has been proposed to regulate soil physicochemical properties and improve soil productivity. However, the response of soil productivity to different rotational tillage with residue return systems remains unclear. Based on this concept, a long-term experiment (2007–2019) concerning conservation rotational tillage with residue-returned was established with four tillage treatments: (1) no-tillage was set at the first year, conventional tillage was set at the second year, and the third year was set with subsoiling (NCS); (2) the first year was set with no-tillage then rotated with subsoiling in the second year (NS); (3) the first year was set with subsoiling then rotated with conventional tillage in the second year (SC); (4) subsoiling (S) was set each year as the control, and all tillage took place after the residue return. After a 12-year in situ tillage experiment, NCS and SC significantly reduced soil bulk density (BD) by 7.4 % and 13.2 %, respectively, and increased soil porosity by 8.8 % and 14.6 %, respectively, in the 0−20 cm soil depth. Meanwhile, NCS, NS and SC increased the macroaggregates by 27.4 %, 22.4 % and 30.0 %, respectively, at the 0−40 cm soil depth, and NCS significantly increased aggregate stability compared with S. For the effect of different tillage practices on soil nutrients, SC slight increased annual average soil organic (SOC) and total nitrogen (TN) by 4.5 % and 7.2 % compared with S. In addition, the soil water balance showed a negative trend of consumption, but NCS, NS and SC mitigated water consumption at the 0−200 cm soil depth, especially in dry years. The 12-year spring maize cultivation consumed soil water storage at a 120−420 cm soil depth, especially in ST, which increased this factor by 28.7 %–34.1 % when compared with others. In normal year, NCS significantly increased yield by 3.7 %–10.4 % compared with others. Considering the effect of the long-term experiment, NCS increased the annual average yield, WUE and PUE by 5.2 %, 4.7 % and 5.6 % compared with S, respectively. Based on the comprehensive Z-index score, the NCS with residue return was selected as the recommended agricultural management measure suitable for the climate-similar region of the Loess Plateau.

Effects of organic fertilizer application on crop yield and soil properties in rice-wheat rotation system: A meta-analysis

To clarify the effects of organic fertilizer application on crop yield and soil properties in rice-wheat rotation system in China, we carried out a meta-analysis to quantitatively evaluate the effects of organic fertilizer types (ordinary organic fertilizer, biochar, and straw), fertilization regimes (organic fertilizer alone, organic fertilizer + partial chemical fertilizer, and organic fertilizer + full amount of chemical fertilizer), and experiment duration (short term, medium term, and long term) on soil properties and the yield of rice and wheat, as well as their responses to soil conditions (acid, neutral, basic). Results showed that the application of organic fertilizer had similar yield-increase effect on rice yield (3.1%) and wheat yield (3.0%) compared to chemical fertilizer application alone. The effect of organic fertilizer application on soil quality was more obvious, significantly reducing soil bulk density by 5.7%, and increasing the concentrations of soil organic matter, total nitrogen, total phosphorus, alkali-hydrolyzable nitrogen, available phosphorus, available potassium, microbial biomass carbon, and microbial biomass nitrogen by 11.7%-38.4%. Among different types of organic fertilizer, the effects of ordinary organic fertilizer and biochar on soil properties improvement were better than straw. Compared to the organic fertilizer application alone, the effects of organic fertilizer combined with chemical fertilizer on crop yield was better, but poorer on soil property improvement. With the increasing duration of organic fertilizer application, crop yield and soil fertility gradually increased. Under the condition of acid soil, the effect of organic fertilizer application on crop yield was the best. The annual yield of rice and wheat showed significant negative correlation with soil bulk density, but a significant positive correlation with the concentrations of soil total nitrogen, available phosphorus, available potassium, and microbial biomass nitrogen.