Vertisols Of Central India Research Articles

Chromium toxicity mediated by application of chloride and sulfate ions in Vertisol of Central India.

Chromium (Cr) is one of the toxic metals adversely affecting organisms including humans in the ecosystems, and it is present in considerable concentration in the tannery industrial effluent. Toxicity expression of Cr is suspected to be influenced considerably by other accompanying ions present in the effluent used for irrigation. In a screen house experiment, interactive effects of chloride and sulfate ions in a Vertisol on uptake of Cr by spinach crop were investigated and treatments imposed were three levels each of Cr (0, 50, 100mgkg-1), chloride (Cl-) (0, 25, 50mMkg-1), and sulfur (S) (0, 4, 8mMkg-1) in possible combinations. Plant growth parameters and leaf Cr concentrations were recorded to find out the effect of anions on Cr dynamics in the plant. Increasing the concentration of Cl- ions in soil reduced the Cr concentration in both root and shoot. Similarly, increasing the concentration of S from 4 to 8mMkg-1 also reduced the concentration and uptake of Cr. Application of sulfate ions augmented the plant growth and counters the negative effect of Cl- ions and Cr. Thus, the study revealed that the addition of S fertilizers could minimize the Cr toxicity in high Cr contaminated soils.

Sustaining Soil Health and Soybean Productivity with Partial Substitution of Nutrients through Gliricidia Green Manuring and Chemical Fertilizers in Vertisols of Central India

The present study was conducted to study the effect of partial substitution of nutrient through gliricidia with chemical fertilizers on soil health and soybean productivity in Vertisols under AICRP for Dryland Agriculture, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola-444104 (M.S.) during 2009-13. The experiment was laid out with nine treatments comprised of application of potassium through chemical fertilizers and gliricidia along with recommended dose of N and P (inorganic source) in a randomized block design with three replications. The pooled data indicated that application of 100% NP + 25 kg K ha-1 + biofertilizers had highest soybean grain yield followed by application of 50% N through glyricidia +50% N through inorganics+ biofertilizers + 25 kg K ha-1 which were on par with each other. The higher SYI and monetary returns were obtained with the application of substitution of 50 % N through gliricidia along with 50 % N through inorganics and biofertilizer which were statistically on par with application 100 % NP along with 25 kg K through chemical fertilizers. The results of the study also indicated significantly higher enhancement in soil organic carbon, residual soil fertility and nutrient uptake by soybean with the application of 50 % N through gliricidia along with 50 % N through inorganics and biofertilizer. Hence, it can concluded that for sustaining soil fertility and soybean productivity with higher economic returns, application of 50% N (25kg ha-1) through glyricidia +50% N through inorganics + biofertilizers + 25kg P2O5 + 25kg K2O ha-1 is recommended as an integrated plant nutrient supply system on Vertisols under dryland condition in central India.

Long-term sustaining crop productivity and soil health in maize–chickpea system through integrated nutrient management practices in Vertisols of central India

Long-term sustainability concerns are growing in agriculture owing to over and under application of fertilizers and poor management of available resources which are resulting into soil health deterioration and declining crop productivity. Balanced and integrated use of organic and inorganic fertilizers is the most logical concept for managing and sustaining long term soil health and crop productivity. Hence, a long-term field experiment was conducted from 2012 to 2017 to develop integrated nutrient management (INM) practices for sustaining crop productivity and maintaining soil health under maize (Zea mays L.) chickpea (Cicer arietinum L.) cropping system in Vertisols of central India. Twelve treatments that comprised of various combinations of general recommended dose (GRD) of NPK, farmyard manure (FYM), poultry manure (poultry manure), urban compost (UC), maize residue (MR), glyricidia loppings (GL) and soil test crop response (STCR) based NPK with target yield 5.0 and 1.50 Mg ha1 in maize and chickpea, respectively were tested. The experiment was conducted following a Randomized Complete Block Design (RCBD) set up with three replications and Simple Random Sampling (SRS) technique of sampling. The results indicated that the grain yield and system yield were observed to be significantly higher with 75% NPK of STCR + FYM at 5 Mg ha1 treatment and recorded an increase of 20.9% and 13.08% in mean grain yield of maize and chickpea, respectively over GRD. The combined analysis results illustrated significant (P < 0.0001) year x nutrient management interaction effect on grain yield with N input (R2 = 0.80) and N uptake (R2 = 0.91). Stepwise multiple regression model also showed that the N input and N uptake significantly (P < 0.05) influenced the system yield under different INM practices. However, apparent nutrient balance was negative for N and K in all treatments except higher level of FYM treatment (FYM at 20 Mg ha1) while P balance was positive under balanced and complete nutrition through organic and inorganic treatments over the years. A significant increase was observed in the various soil health indicators (physical, chemical and biological) under balanced and integrated use of organic and inorganic fertilizers. FYM, poultry manure and urban compost improved the physical properties of soil like mean weight diameter (MWD), water stable aggregates (WSA), bulk density and porosity. The application of higher level of FYM (20 Mg ha1) significantly increased the soil organic carbon (SOC) (6.30 g kg1), SOC stock (11.8 Mg ha1), carbon sequestration rate (213.1 kg ha1 year1), KMnO4-N (121.7 mg kg–1), Olsen-P (23.8 mg kg–1) and NH4OAc-K (273.5 mg kg–1) concentration in surface soil as compared to GRD and control treatments. The soil enzymes, dehydrogenase (DHA), alkaline phosphates (Alk-P) and fluorescein diacetate (FDA) were enhanced significantly with the application of FYM at 20 Mg ha1 and STCR based 75% NPK + FYM at 5 Mg ha1. The STCR based 75% NPK along with FYM at 5 Mg ha1 treatment recorded highest sustainable yield index (SYI) 0.84 and 0.92 with maximum guaranteed yield of 6.19 and 1.99 Mg ha1 in maize and chickpea, respectively. The results indicate that the chickpea yield was more sustainable as compared to the maize.

Soil organic carbon, dehydrogenase activity and fluorescein diacetate as influenced by contrasting tillage and cropping systems in Vertisols of Central India

Soil organic carbon, dehydrogenase activity and fluorescein diacetate as influenced by contrasting tillage and cropping systems in Vertisols of Central India

Effects of Bt-cotton on biological properties of Vertisols in central India

ABSTRACTGrowing areas under transgenic crops have created a concern over their possible adverse impact on the soil ecosystem. This study evaluated the effect of Bt-cotton based cropping systems on soil microbial and biochemical activities and their functional relationships with active soil carbon pools in Vertisols of central India (Nagpur, Maharastra, during 2012–2013). Culturable groups of soil microflora, enzymatic activities and active pools of soil carbon were measured under different Bt-cotton based cropping systems (e.g. cotton-soybean, cotton-redgram, cotton-wheat, cotton-vegetables and cotton-fallow). Significantly higher counts of soil heterotrophs (5.7–7.9 log cfu g−1 soil), aerobic N-fixer (3.9–5.4 log cfu g−1 soil) and P-solubilizer (2.5−3.0 log cfu g−1 soil) were recorded in Bt-cotton soils. Similarly, soil enzymatic activities, viz. dehydrogenase (16.6–22.67 µg TPF g−1 h−1), alkaline phosphatase (240–253 µg PNP g−1 h−1) and fluorescein di-acetate hydrolysis (14.6–18.0 µg fluorescein g−1 h−1), were significantly higher under Bt-cotton-soybean system than other Bt- and non-Bt-cotton based systems in all crop growth stages. The growth stage-wise order of soil microbiological activities were: boll development > harvest > vegetative stage. Significant correlations were observed between microbiological activities and active carbon pools in the rhizosphere soil. The findings indicated no adverse effect of Bt-cotton on soil biological properties.

Impact of Long-Term Application of Sewage on Soil and Crop Quality in Vertisols of Central India.

Shortfall of rain and the decreased groundwater level force farmers to use poor quality water for crop production in developing countries. In this study, the quality of agricultural produce and soil health affected by sewage water (Patranala) irrigation was evaluated. Sewage sediment, soil and crop samples were analyzed for physico-chemical properties. Sewage water found to contain trace concentration of heavy metals. However, long-term application of this water for crop production could build up a significant amount of trace metals in both soil and sediments. The DTPA extractable heavy metals ranged Cu 2.7-7.59, Cd 0.04-0.06, Pb 1.29-2.05, Cr 0.01-0.04, Ni 0.24-1.03 and Zn 0.63-2.59mgkg-1 soil. The heavy metal risk assessment (hazard quotient, HQ) was calculated and found that HQ for these metals in the crops under study was in safe limits. From the study, it is concluded that growing vegetables using sewage water of Patranala is safe, but periodic monitoring to be carried out to avoid food chain contamination.

Impact of Distillery Effluent on Soil Carbon and Nitrogen Dynamics in a Vertisol of Central India

ABSTRACTDistilleries produce a huge quantity of effluents, popularly known as spent wash (SW), which when bio-methanated produce post-methanation effluents (PME). A field experiment on soybean–wheat system was conducted for five consecutive years in a Vertisol of central India to evaluate the effect of distillery effluent (DE) on soil carbon and nitrogen dynamics. Ten treatment combinations consisting of control, 100% NPK + Farmyard Manure (FYM), and graded level of SW and PME were applied. Total carbon content of soil increased significantly with applications of FYM and DE. SW was found superior in enhancing carbon content of soil in comparison to PME. Farmyard Manure contributed more carbon toward the recalcitrant pool, whereas DE contributed more carbon toward the active and slow pool. Nitrogen (N) availability was significantly improved with the application of DE. Balanced application of DE may act as amendment for increasing C and N stocks in Vertisol.

Soil Enzymatic Activities as Influenced by Lead and Nickel Concentrations in a Vertisol of Central India.

A pot-culture was conducted in Completely Randomized Design with three replicates to study the effect of Pb and Ni on enzymatic activities in a Vertisols. Results indicated that increasing in the levels of Pb from 0, 100, 150 and 300mgkg-1 soil significantly reduced the dehydrogenase activity (DHA) 38.9, 32.1, 30.9, 18.1µg triphenylformazang-1 soil 24h-1; acid phosphatase activities 73, 61, 58, 55µg PNPg-1 soil h-1 and alkaline phosphatase activities 80.7, 69.4, 66.2 and 64.0µg PNPg-1 soil h-1, respectively. Application of Ni up to 100mgkg-1 had significantly improved the soil enzymatic activities and thereafter there was no such change up to the highest level (300mg Nikg-1). Among soil enzymatic activities, DHA was more sensitive to Pb application. The findings generated through this study can be useful for managing waste water for safe disposal as well as sustainable crop production.

Symbiotic Efficiency of Slow and Fast-Growing Soybean Rhizobia of Central India

Soybean rhizobia are pre-dominantly slow growing but fast growing strains that evolved from natural populations have been reported globally including from several locations in India but have not been evaluated. The symbiotic effectivity of three slow and three fast-growing rhizobial strains isolated from Vertisols of Central India was evaluated on soybean var. 9752 in sterilized sand microcosms in a green-house. At 40 days growth, there was variation in nodulation parameters and growth of soybean with both types of rhizobia but overall, the slow growers were superior to fast growers with respect to nodule number (56%), nodule dry matter (25%), shoot dry matter (11%) and total nitrogen uptake (22%). The slow-growers (genetic homology to Bradyrhizobium japonicum) fixed ~ 25% more nitrogen than fast-growers with homology to Rhizobium (Agrobacterium) radiobacter. The results have very important implications for strain selection during biofertilizer production to maximize biological nitrogen fixation.

Inter/mixed cropping of lentil (Lens culinaris) in late sown wheat (Triticum aestivum L.) for higher productivity and profitability of wheat in vertisols of Central India

Inter/mixed cropping of lentil (Lens culinaris) in late sown wheat (Triticum aestivum L.) for higher productivity and profitability of wheat in vertisols of Central India

Soil Hydro-thermal Regimes as Affected by Different Tillage and Cropping Systems in a Rainfed Vertisol

The present investigation was aimed to study the short-term effect of different tillage and cropping systems on soil hydro-thermal properties under conservation agriculture (CA) practices. The field experiment consists of three different tillage systems [viz., conventional tillage (CT), reduced tillage (RT) and no-tillage (NT)] and four cropping systems [viz., soybean (Glycine max) + pigeon pea (Cajanus cajan) intercropping (2:1), soybean – wheat (Triticum durum), maize (Zea mays) + pigeonpea intercropping (1:1), and maize – gram (Cicer arietinum)]. Results indicated that the surface layer (0-5 cm depth) recorded higher moisture content that decreased with increasing soil depth. The data on soil moisture retention at field capacity (FC) was not significantly influenced by tillage and cropping systems. Among different tillage systems, NT (38.9%, v/v) and RT (38.2%, v/v) recorded higher water content at field capacity than CT (37.5%, v/v). Similar to field capacity, soil moisture retention at permanent wilting point (PWP) was not influenced either by tillage or by cropping systems. Tillage and cropping systems had no significant effect on soil temperature recorded during rabi season. It was observed that tillage system, depth and their interaction (tillage × depth) had a significant effect on volumetric heat capacity in dry and saturated soil. Results showed that reduced tillage (0.68%) and no-tillage (0.67%) registered significantly (P < 0.05) higher soil organic carbon (SOC) than CT (0.62%) in the 0-5 cm layer. Study results reinforce the significance of CA practices, which is not only affecting soil hydro-thermal properties (soil moisture, temperature and volumetric heat capacity) but also favourably influencing bulk density, porosity and SOC in a Vertisol of Central India.

Interactive effect of cadmium and zinc on chromium uptake in spinach grown in Vertisol of Central India

A pot culture experiment was conducted to study impact and interaction of multi-metals on growth, yield and metals uptake by spinach (variety All Green). Three levels of each chromium (0, 50 and 100 mg/kg), cadmium (0, 1 and 2 mg/kg) and zinc (0, 10 and 20 mg/kg) in combinations (total treatments 3 × 3 × 3 = 27) were applied in a Vertisol (5 kg). The results showed that increasing the concentration of chromium, cadmium and zinc in soil enhanced the respective metal concentrations in spinach root and shoot. When cadmium at 2 mg/kg along with chromium at 100 mg/kg soil was applied, chromium concentration and uptake were decreased in root and shoot. Meanwhile, zinc application had no significant effect on chromium uptake and concentration in spinach biomass. From the results, it was concluded that cadmium at higher dose had an antagonistic effect over chromium. On the other hand, in chromium, cadmium and zinc combinations particularly at their higher levels, a competition among each other was found. Therefore, the findings could be used as guidelines for controlling and management of heavy metals pollution in farmland.

Water and nutrient management effects on water use and yield of drip irrigated citrus in vertisol under a sub-humid region

Scarcity of water and nutrients in orchards are the major causes of low productivity and decline of citrus in tropics. With a hypothesis that the optimal amount of water and nutrients application through drip irrigation (DI) could save substantial irrigation and fertilizers comparative to that under traditional basin irrigation (BI) with band placement of fertilizer (BPF), this study was conducted in citrus in vertisol of central India. Three DI regimes: I1, I2 and I3 scheduled at 50% class-A pan evaporation rate (Ep), 75% Ep, and 100% Ep along with three fertilizer doses: F1, F2 and F3 at 50% recommended dose of fertilizer (RDF, N:P2O5:K2O=600 g:200 g:100 g), 75% of RDF and 100% of RDF were applied to mandarin plants respectively. BI with band placement of fertilizer (BPF) at 100% RDF was taken for comparison. All the drip-fertigation treatments (except I1F1) produced higher plant growth and fruit yield, with better quality fruits compared with BI+BPF. The highest fruit yield (16.39 t ha−1), water use efficiency (3.9 kg m−3) and fertilizer use efficiency (87.3 kg kg−1) were observed in I2F2. The concentrations of N, K and Fe in leaves were significantly higher in I2F2 compared to other treatments. The leaf photosynthesis, stomatal conductance (Gs) and transpiration were the highest in I3F3. However, leaf water use efficiency (LWUE, photosynthesis/transpiration) was the highest in I2F2. The overall results of this study demonstrated that the application of optimum quantity of water and fertilizers (I2F2) through DI could be a productive and water efficient option in citrus production in vertisol.

Population ecology of soybean-rhizobia in diverse crop rotations in Central India

Ensuring adequate populations of effective rhizobia in soil is essential to guarantee optimum nodulation and nitrogen fixation in legumes. The population of soybean-rhizobia and the proportion of slow and fast growers were enumerated in Vertisols of central India in different crop rotations for three years during 2013-15. Soils were from soybean-based (soybean-wheat and soybean-chickpea) and cereal-based rotations (maize-wheat, rice-wheat and maize-chickpea) rotations. Soybean-based rotations stimulated the rhizobial population by 22-fold compared to cereal rotations. Lowest populations were in the summer but increased in soybean rotations by 13.3-fold after the rainy season to 2743cellsg−1 soil at maximum vegetative growth. In the cereal rotations, the increase was by 1.7-fold to 61cellsg−1 soil. Long-term integrated nutrient management, by annual application of farmyard manure in soybean along with chemical fertilizers, improved the rhizobial numbers by 1.5-fold over chemical fertilization alone and by 2.9-fold over unfertilized treatments. Increased crop growth by chemical fertilizers also stimulated rhizobial populations by 1.9-fold over unfertilized soybean. The proportion of slow-growing soybean rhizobia was lower in soybean-based rotations (38%) compared to cereal-based rotations (62%), showing that continued soybean growth led to a greater proliferation of fast-growing rhizobia. Application of farmyard manure did not change the proportion of slow growers. The proportion of slow growers was ∼15% more in winter compared with the summer populations. The slow growers were symbiotically superior, producing greater dry matter and nodule mass (+12%), with more biologically fixed nitrogen (+18%) than the fast growers. Results highlight the importance of crop rotation with cereals, application of organic amendments along with chemical fertilizers and selection of slow-growing rhizobia as inoculants.

Short-term effect of conservation agriculture practices on soil quality of a vertisol in central India

A field experiment was conducted to assess the effect of contrasting tillage systems viz., no-tillage, reduced tillage and conventional tillage with four cropping systems viz., soybean + pigeon pea (2:1), soybean - wheat, maize + pigeon pea (1:1) and maize - chickpea on yields and soil quality in a Vertisols of Central India. Surface soil samples were collected and analyzed for physicochemical properties. Correlation analysis of seven soil physicochemical attributes showed a significant correlation in eight (P < 0.01) and four (P < 0.05) attribute pairs out of the 49 soil attribute pairs. The results revealed that the soil properties such as soil reaction (pH), electrical conductivity, organic carbon, mean weight diameter, available nitrogen, available phosphorus and available potassium were influenced by tillage and cropping systems. Evaluation of soil quality using soil quality index (SQI) under different tillage and cropping system showed that soil quality was better in maize + pigeon pea (1:1) and soybean + pigeon pea (2:1) under reduced tillage and no tillage as compared to the other systems. The tillage that caused destructive effects on soil quality should be discouraged for long-term cultivation to maintain good soil health for sustainable agricultural production. The value of SQI was positively and significantly correlated with soybean grain equivalent yield for all the tillage and cropping system. This indicates that the index parameters may be used for computing the soil quality under different management practices.

Crop Residue Retention and Nutrient Management Practices on Stratification of Phosphorus and Soil Organic Carbon in the Soybean–Wheat System in Vertisols of Central India

ABSTRACTThe long-term crop residue retention coupled with external nutrient inputs are crucial for maintaining soil phosphorus (P) and soil organic carbon (SOC) in Vertisols of Central India. A study was conducted to evaluate the long-term effect of three wheat residue management practices (residue burning, incorporation, and surface retention) in combination with three supplementary nutrient inputs (SNI) [control, fertilizer, and farmyard manure (FYM)] on stratification of P and SOC in the soybean–wheat system in Vertisol. The wheat residue either incorporated or retained on the soil surface increased the availability of P and SOC content as compared to the common practices of residue burning. Residue retention or incorporation increased stratification of P and soil organic carbon over the residue burning. Irrespective of the nutrient treatments, greater stratification ratio of SOC and P were registered under wheat residue incorporation or retention compared to residue burning. It is evident from the study that wheat residue incorporation or retention plus addition of FYM could be an effective strategy for increasing the soil fertility in a soybean–wheat system of Vertisols of Central India.

Long-term Conservation Tillage Effect on Soil Organic Carbon and Available Phosphorous Content in Vertisols of Central India

Efficient nutrient management in conservation tillage is one of the major concerns in vertisols as residue retention on soil surface and reduction in tillage operation can have a major impact on nutrient dynamics and stratification. The present study examined profile distribution of soil organic carbon (SOC) and available phosphorous under long-term (12 years) imposition of four different tillage systems, namely conventional tillage (CT), mouldboard tillage (MB), reduced tillage (RT), no tillage (NT) and three nitrogen levels, viz. N50%, N100% and N150%. In 0- to 5-cm soil layer, highest and lowest SOC was observed in NT (8.8 g kg−1) and CT (5.9 g kg−1), whereas in 5- to 15-cm soil layer, higher SOC was observed in MB. The stratification ratio of SOC was higher in NT (2.20) followed by RT (1.93), MB (1.68) and CT (1.51). Higher available phosphorous concentration (12.8 g kg−1) was recorded in NT with N50% followed by NT with N100%. Over the year, no significant effect of tillage on soybean and wheat yield was observed. However, effect of N level on yield was significant. Overall, conservation tillage practice imposed no penalty on yield of soybean–wheat system, while it saved energy and time by reducing the number of tillage operations.

Effect of soil-test-based long-term fertilization on soil health and performance of rice crop in Vertisols of central India

The present investigation was carried out to study the effect of soil-test-based long-term fertilization on soil health and performance of rice crop in Vertisols of Central India. The experiment was started in 2007–08 consisting six treatments viz. Control (No fertilizers), General Recommended Dose (GRD) (12060-40), STCR based for 4 t ha−1 target, STCR based for 5.5 t ha−1 target, STCR based for 4 t ha−1 target + 5 t FYM ha−1 and STCR based for 5.5 t ha−1 target + 5t FYM ha−1 and with four replications. The crop cultivar of rice MR-219 was grown with different treatments and performance in terms of grain yield and straw yield were recorded at harvest of the crop. The soil chemical and biological properties were assessed by analyzing the soil samples after harvest of the crop collected from 0–15 cm depth. Experimental data was statistically analyzed by the standard analysis of variance technique appropriate to randomized block design to test the significance of treatment effects. The results of the study revealed that, balanced fertilization based on soil test recorded higher yield of rice over general recommended dose of fertilizers.

Rooting behaviour of chickpea (Cicer arietinum) as affected by soil compaction levels in Vertisol of central India

Soil compaction may restrict deep root growth and adversely affect plant access to sub-soil layer. Therefore it is important to study rooting behaviour of crops to soil compaction that are imparted on it naturally or artificially. The objective of this study was to determine the effect of soil compaction levels by varying the soil bulk density (BD) on rooting parameters and to model the root growth to understand the dynamics of rooting behaviour of chickpea (Cicer arietinum L.). Compaction level treatments, i.e. BDs were (i) 1.2, (ii) 1.4, (iii) 1.5 and (iv) 1.6 Mg/m3. When BD was increased from 1.2 Mg/m3 to 1.6 Mg/m3, there was 58% and 44% reduction in plant height of JG 11 and JG 130, respectively. There was 59% and 45% reduction in root length of JG 11 and JG 130, with increase in BD from 1.2 Mg/m3 to 1.6 Mg/m3. On an average, an increase in BD by 0.1 unit resulted in 19.34 and 19.11% decrease in root main axis length of JG 11 and JG 130, respectively. There was a negative correlation between root penetration rate and soil BD (R2 = 0.88). The critical growth limiting BD for chickpea was found to be 1.89 Mg/m3 in our study. The logistic growth model was fitted well with the observed dataset obtained from study with R2 of 0.98** (P &lt; 0.01). In this study, the chickpea variety JG 130 proved to be better than JG 11 while selecting chickpea cultivars for highly compacted soils.

Tillage and Manure Induced Changes in Carbon Storage and Carbon Management Index in Soybean–Wheat Cropping System in the Vertisols of Central India

Conservation tillage as part of conservation agriculture is regarded as a potential mitigation strategy to enhance the sink for atmospheric carbon in agriculture. Though, conservation tillage has been tested for its efficacy in other parts of the globe, very few information exists with regard to its C sink potential in Indian context, particularly for Vertisols of central India. Therefore, the present study was undertaken in the Vertisols of Bhopal to assess the effect of conservation tillage with or without application of manure, on carbon sequestration and carbon management index in soybean–wheat cropping system. After 4 year cropping cycle, it was observed that conversion from conventional to conservation tillage with application of manure (2.0 Mg ha−1 FYM-C) every year showed the highest impact on soil carbon sequestration and carbon management index. Under a particular manure treatment, carbon storage was higher under no-tillage in the 0–5 cm soil depth, whereas it was higher under reduced tillage in the 5–15 cm soil layer.