Non-tilled Soil Research Articles

Sporulation and Dispersal of the Biological Control Agent Aspergillus flavus AF36 Under Field Conditions.

Aflatoxins are carcinogens produced by the fungi Aspergillus flavus and A. parasiticus that contaminate pistachio crops. International markets reject pistachio when aflatoxins exceed permitted maximum levels. Releasing the atoxigenic strain AF36 of A. flavus is the leading aflatoxin pre-harvest control method. The product AF36 Prevail, sorghum grains coated with AF36 propagules, has been used in California since 2017. However, a high percentage of grains of the Prevail fail to sporulate in orchards. Here, the effect of soil moisture on the percentage of AF36 product grains sporulating (SG) and the quantity of spores per grain using a sporulation index (SI) was determined. Under controlled conditions, SG was higher than 85% when soil moisture was 13% or more, and SI increased with increasing soil moisture from 8.4 to 21%. The highest AF36 sporulation occurred near the micro-sprinklers when the grains were not impacted by the irrigation water drops. Arthropod predation was responsible for lost product grains, which was more pronounced in non-tilled soil than in tilled soil. Dispersal of the AF36 spores decreased markedly with the height and distance from the inoculum source, following a pattern of diffusion equations. However, AF36 spores easily reached canopies of pistachios located 10 m from the inoculum source. Our results indicate that AF36 Prevail should be applied close to the irrigation line in the moist soil area but avoiding the areas where excess irrigation causes water accumulation. The biocontrol of aflatoxins in California's pistachio production areas was optimized by improving the field realization of the biological control agent.

Olive Tree Physiology and Productivity Responses under No-Tillage or Digestate Amendment in an Acid Clay Soil

In Mediterranean countries characterized by increasingly extended hot and dry periods, olive trees are often conventionally practiced in low fertility and rainfed soils. This study investigated over a 15-month period how conventional tillage, combined with or without incorporated solid digestate, and no tillage affected selected soil properties, photosynthetic activity and productivity of mature olive trees growing in highly clayey acid soil with an unbalanced nutrient content and Mn excess. Neither in soil nor in drupes were Mn, Fe, Cu and Al contents affected by the managements. However, in soil, exchangeable Mn that was always larger than 200 mg kg−1 threshold and unbalanced Ca, Mg, and K contents were evidenced in all treatments. Non-tilled soil showed the highest (p < 0.05) stomatal conductance and photosynthetic rate, and the highest (p < 0.05) fruits and oil yields. Instead, conventional tillage negatively (p < 0.05) affected plant physiology and productivity, likely due to the tilled increase in aeration, enhancing soil water loss and organic C mineralization. Conversely, digestate addition increased TOC, TN and EC. Stomatal conductance, the photosynthetic rate and plant yield significantly recovered (albeit not to no-tillage values) in tillage combined with incorporated digestate, suggesting that digestate-derived organic matter created soil conditions less constraining to plant growth and productivity than the conventional tillage did. Dealing with soil properties and climatic conditions is the key for adopting the best management practice for preserving plant productivity and soil fertility.

Effects of shallow non-inversion tillage on sandy loam soil properties and winter rye yield in organic farming

Due to an expected improvement of soil quality and soil water storage, the substitution of mouldboard ploughing by reduced tillage was identified as a potential climate change adaptation measure for organic farming in a relatively dry region with a humid continental climate. In a field trial on a sandy loam soil in eastern Germany, reduced tillage was carried out to 6 cm soil depth by means of a ring cutter and compared to mouldboard ploughing with 25 cm tillage depth. In the present study, the influence of ring cutter tillage on soil properties was investigated for the first time. The effects of shallow ring cutter tillage on soil physical parameters, soil organic matter distribution, soil mineral nitrogen content, total nitrogen uptake by the crop, root content, and grain yield of organically grown winter rye (Secale cereale L.) were analysed in the uppermost 20 cm of a sandy loam soil and compared to those of mouldboard ploughing.Under ring cutter tillage, soil bulk density was in 8–20 cm soil depth by up to 15% higher than under mouldboard ploughing. In 9–15 cm soil depth, ring cutter tillage resulted in smaller contents of coarse macropores and mesopores, more micropores, and an 11% smaller available water capacity compared to mouldboard ploughing. The total nitrogen uptake by winter rye was in the ring cutter treatment by up to 44% smaller than in the mouldboard plough treatment. Root content was up to 209% higher in 1–6 cm soil depth and up to 71% smaller in 8–20 cm soil depth after ring cutter tillage than after mouldboard ploughing. Winter rye yield declined by 22–43% in the ring cutter treatment relative to the mouldboard plough treatment.Shallow ring cutter tillage resulted in a root growth-restricting soil compaction in the non-tilled soil layers below 6 cm depth and led to a limitation of nitrogen mineralisation until spring. Both effects likely caused the considerable reduction of crop yield. The results suggest that shallow ring cutter tillage in organic farming seems to be not suitable for sandy loam soils as long as the risk of a soil compaction-induced limitation of root growth and nitrogen supply cannot be minimised.

Modeling the Dynamics of Soil Organic Matter Accumulation from Leaf Litterfall as Affected by Tillage Practices in Mango Orchard

This study was undertaken to determine long-term soil organic matter (SOM) accumulation dynamics from added mango leaf litter (MLL) into tilled (MT) and non-tilled soil (MnT) through integrated field experiment (bio-physico-chemical edaphic properties) and system dynamics modeling. Field data shows that the coarse (Lf) and fine (Fn) fractions of SOM have no significant difference (p > 0.05) between MT and MnT during the dry season. In contrast, there is a significant difference (p < 0.01) in the Fn fraction between MT and MnT during the wet season. The total N, available P, exchangeable K, as well as the collembola, bacteria, and fungi in the soil were also assessed. Of these parameters, the available P and exchangeable K have a significant difference between the MnT and MT during the dry season. In comparison, the total N and collembola significantly differed during the wet season. The results of the field experiment were used in the parametrization to build the SOM accumulation model. The 20-year simulation showed that the incorporation of MLL into the soil through tillage increased SOM from 3.09% to 3.13%, with an average of 2.78 ± 0.018%. In the non-tilled orchard, SOM also increased from 3.09% to 4.23%, with an average of 3.59 ± 0.035%. This SOM level can sustain the fertility and productivity of the mango agroecosystem. The increase in SOM is accounted for by the coarse fraction both in tilled and non-tilled plots. Given the foregoing, with minimum tillage, mango orchards can be developed into crop-based systems.

Nitrogen uptake and biochemical activity in maize rhizosphere during growth on acidic and neutralized soils

This work aimed to understand the effects of liming and no tillage on the pH stability and inorganic N uptake in the rhizosphere of maize plants on an acidic soil depleted in organic matter, reclaimed by liming and no tillage in a long-term field trial. We analyzed the inorganic N dynamics, respiration, microbial biomass and enzyme activities in the rhizosphere and bulk soil of maize plants grown in rhizoboxes on acidic soil under conventional tillage or no tillage management with or without liming and amendment (sugar beet foam and red gypsum). Analysis of inorganic N in the rhizosphere showed preferential NH4+-N uptake and reduced NO3−-N uptake by maize plant grown on acidic non tilled soil. With few exceptions, soil respiration, microbial biomass and enzyme activities were higher in the maize rhizosphere than in bulk soil. Soil respiration and enzyme activities were generally higher in the rhizosphere of non-tilled soils, whereas microbial biomass was higher in the rhizosphere of the amended soils. The study, based on rhizobox, showed effectiveness of sugar beet lime and red gypsum in the neutralization of the pH value in the rhizosphere during the early stages of maize growth, and the limited capacity of the plant to neutralize the acidic soil pH value in the rhizosphere of the non-amended soil. Positive interactive effects of tillage and liming were observed on the biochemical activity in the plant rhizosphere that could contribute to explain the positive effects of this management practice on the soil fertility observed at field scale on the long term.

Biological and synthetic approaches to inhibiting nitrification in non-tilled Mediterranean soils

BackgroundThe increasing demand for food production has led to a tenfold increase in nitrogen (N) fertilizer use since the Green Revolution. Nowadays, agricultural soils have been turned into high-nitrifying environments that increase N pollution. To decrease N losses, synthetic nitrification inhibitors (SNIs) such as 3,4-dimethylpyrazole phosphate (DMPP) have been developed. However, SNIs are not widely adopted by farmers due to their biologically limited stability and soil mobility. On the other hand, allelopathic substances from root exudates from crops such as sorghum are known for their activity as biological nitrification inhibitors (BNIs). These substances are released directly into the rhizosphere. Nevertheless, BNI exudation could be modified or even suppressed if crop development is affected. In this work, we compare the performance of biological (sorghum crop) and synthetic (DMPP) nitrification inhibitors in field conditions.ResultsSorghum crop BNIs and DMPP prevented an increase in the abundance of ammonia-oxidizing bacteria (AOB) without affecting the total bacterial abundance. Both nitrification inhibitors maintained similar soil NH4+ content, but at 30 days post-fertilization (DPF), the sorghum BNIs resulted in higher soil NO3− content than DMPP. Even so, these inhibitors managed to reduce 64% and 96%, respectively, of the NO3−-N/NH4+-N ratio compared to the control treatment. Similar to soil mineral N, there were no differences in leaf δ15N values between the two nitrification inhibitors, yet at 30 DPF, δ15N values from sorghum BNI were more positive than those of DMPP. N2O emissions from DMPP-treated soil were low throughout the experiment. Nevertheless, while sorghum BNIs also maintained low N2O emissions, they were associated with a substantial N2O emission peak at 3 DPF that lasted until 7 DPF.ConclusionsOur results indicate that while sorghum root exudates can reduce nitrification in field soil, even at the same efficiency as DMPP for a certain amount of time, they are not able to prevent the N pollution derived from N fertilization as DMPP does during the entire experiment.Graphic

Dynamics of Glyphosate and Aminomethylphosphonic Acid in Soil Under Conventional and Conservation Tillage

This study investigates the adsorption and dissipation of glyphosate and the formation/dissipation of AMPA in non-tilled (NT) and conventionally tilled (CT) soil at 0–5 and 5–20 cm depth. Glyphosate adsorption was mainly related to the different NT and CT soil properties (clay and amorphous Al oxides), whereas an effect of the soil management could not be identified. Glyphosate dissipation was initially fast, and it slowed down later. The initial glyphosate concentration in NT soil at 0–5 cm was significantly lower than the dose applied due to the interception by the weeds and crop residues. AMPA began to form early after treatment and persisted longer than glyphosate. The DT50 range was 8–18 days for glyphosate and 99–250 days for AMPA. Longer glyphosate and AMPA DT50 were observed in NT soil compared to CT soil but, for glyphosate, the difference was significant only at 5–20 cm. Higher glyphosate and AMPA concentrations were detected in NT than in CT soil at the end of the study at 0–5 cm. The differences in glyphosate and AMPA DT50 and persistence were mainly attributable to the influence of different NT and CT soil characteristics. However, other factors could have contributed to the different glyphosate and AMPA dynamics between the soils, like glyphosate wash-off from crop residues on NT soil with the rainfall, the delayed glyphosate return to the soil by weed root exudation or weeds decomposition, and the NT soil compaction which may have reduced the microbial degradation of glyphosate at low concentrations.Graphic abstract

One-shot classification-based tilled soil region segmentation for boundary guidance in autonomous tillage

In recent years, machine vision has been frequently used to estimate local paths for autonomous tractors. The incorporation of deep learning-based techniques to its methodology is expected to induce robust performance under practical field conditions. Typical tillage of autonomous tractors requires the tilled soil region detection to provide the local paths, which are usually determined based on the boundaries between tilled and non-tilled soil. However, tilled soil regions usually exhibit different feature distributions by field (domain) in terms of factors like soil characteristics, crop type, and method of tillage. This makes the development of deep learning-based systems with highly generalizable performance difficult. In this study, this issue is addressed by proposing a few-shot learning (FSL)-based effective tilled soil region segmentation, which is utilized to detect tilled soil region in 2D perspective scenes to provide tillage path guidance to autonomous tractors. The proposed approach used an image patch classification-based field region segmentation pipeline as the backbone and a one-shot classification model was designed to classify each image patch as tilled or non-tilled soil. The tilled soil region is then segmented by clustering the image patches belonging to the corresponding classes. The results demonstrate that one-shot classification exhibits a classification accuracy exceeding 0.9 over the entire dataset obtained from various fields, including new data, while the typical classification method exhibits a classification accuracy of approximately 0.74 on new data. Further, segmentation is successfully performed on the detected tilled soil regions belonging to various domains. In conclusion, the proposed method can provide the relative feature difference between tilled and non-tilled soils, allowing for expansion to new data without fine-tuning. This robust field region segmentation can be utilized practically as an essential skill to support the tillage path decision for an autonomous tractor.

Depth distribution of soil organic matter and burrowing activity of earthworms—mesocosm study using X-ray tomography and luminophores

Earthworms feed on organic matter present at the soil surface or within the soil. Thus, its distribution in the soil profile is likely to greatly influence earthworm behavior and, in turn, their burrow system. To test this idea, two anecic and two endogeic earthworm species were introduced into repacked soil cores (depth = 30 cm) upper half filled with a top soil containing 4% organic matter (0–15 cm) and lower half filled with a deep soil at 2% organic matter (15–30 cm). Earthworm behavior was studied using X-ray tomography combined with luminophores (colored particulate tracers of 63–125 μm size) placed at 0, 3, and 12 cm depth, a method widely used in sediment ecology. We observed that anecic and endogeic earthworms had contrasting reactions to the conditions with only endogeic species burrowing more intensively in the upper part. From a quantitative point of view, only a few percent of luminophores were displaced. However, luminophore displacements also provided qualitative information to complement the tomography: (i) endogeic species and especially Aporrectodea caliginosa bioturbated the most soil close to the surface (3 cm depth) and (ii) the two anecic species influenced the luminophore distribution differentially with Lumbricus terrestris displacing significantly more luminophores, whatever their initial depth, than Aporrectodea nocturna due to intense surface cast activity. Beyond methodological developments, our study found that endogeic earthworms burrow more in zones with higher organic matter contents and this explains why they are mainly found close to the soil surface in non-tilled soils.

Incorporation of Rice Residues Through Tillage Enhances Soil Organic Matter Accumulation in Rice Land

Soil organic matter (SOM) is a critical determinant of the fertility status and productivity of soil, yet SOM status in rice land is degrading. This study was conducted through integrated in situ experimentation (collembola, bacteria, fungi, moisture, temperature, N, P, K) and modeling to determine how to enhance SOM in rice land. An approach to increase SOM by incorporation of rice residues (straw and stubble) through tillage was done. While previous SOM assessment only looked into fine particles (< 0.05 mm, Fn), this study includes both fine and coarse (0.05–2 mm, Lf) SOM fractions. Incorporation of rice residues by tillage increased Lf by 27% (P < 0.001 at 0.05α) while it decreased Fn by 7% (P = .006 at 0.05α). Long-term projection of SOM status generated using system dynamics (SD) modeling showed higher accruals of Lf in the tilled soil due to the physical fragmentation of rice residues. The accumulation of Fn in non-tilled soil was attributed to the synergistic effect of collembola, bacteria, and fungi on the further decomposition of available Lf. Incorporation of 15 T ha–1 yr–1 of rice residues showed accrual of SOM at a rate of 0.03% yr–1. SOM state was observed to decline at –0.003% yr–1 when rice residue incorporation was reduced to 10 T ha–1 yr–1 with a rate of –0.003% yr–1, and –0.04% yr–1 when the residues were further cut down to 5 T ha–1 yr–1. Continuous practice of rice residue incorporation at 20 T ha–1 yr–1 showed tenable SOM accrual and projected to contain > 4.0% within 25 yr. Contrary to previous work, this study showed that incorporating rice residues through tillage enhanced the Lf fraction and, consequently, increased the total SOM.

Comparison of the Effects of Different Crop Production Systems on Soil Physico-Chemical Properties and Microbial Activity under Winter Wheat

In many areas, organic crop production systems have been shown to contribute to maintaining good soil condition. The organic production system has been recommended as an alternative to conventional agriculture. However, in order to recommend this practice in new regions, it is necessary to obtain information about its effects and consequences in local environmental conditions. The research was completed during 2016–2018 in Osiny (Lublin region, Poland) on a field experiment established 26 years previously in a Haplic Luvisol soil. The research was aimed at comparing the effects of long-term use of tilled soil with organic (ORG) and conventional (CON) crop production systems with those in non-tilled soil under permanent grass (PRG) as a control. This comparison was done on the basis of changes in the values of soil properties as follows: Total porosity (TP), total organic matter (OM), particulate organic matter (POM), humic substances (HS), water-extractable carbon (WEC), microbial biomass carbon pool (MBC) and dehydrogenase activity (DH). Soil samples were collected from experimental fields (each treatment 1 ha) under winter wheat and permanent grass each year from 0–5, 5–10, 15–20 and 30–35 cm depths. Over the three year study period, it was found that permanent grass and the organic crop production system contributed to increased soil OM, POM, HS, WEC and MBC contents and DH activity compared to the CON system, especially in the top soil layer, 0–5 cm. To obtain a clearer picture of soil quality change our study examined for the first time the metabolic potential index (MPI) as a ratio of dehydrogenase activity to the soluble organic carbon content. The MPI values confirmed the increase of metabolism in ORG soil as a consequence of management practices compared with CON soil. The obtained correlations showed strong mutual relationships within properties of the heterogeneous soil complex. The results show the positive effects of the ORG management system causing soil condition improvement which is based on organic fertilization, enriching the soil with a large amount of plant residues in creating positive changes in the soil quality in contrast to the CON system.

Soil water retention and hydraulic conductivity dynamics following tillage

Soil bulk density (ρb) may be purposely reduced in agricultural fields using tillage to improve hydraulic properties. However, tillage alters the soil structure, resulting in unstable soils. As the soil stabilizes, ρb increases over time. While this is known, studies on soil hydraulic properties in tilled soils, including comparisons between tilled and non-tilled soils, commonly assume a rigid soil structure. This study presents changes in soil water retention and saturated hydraulic conductivity (Ksat) as ρb increased dynamically with time following tillage at a loam-textured field site. Over the summer of 2015, soil cores were collected at several depths below the surface following precipitation events. Soil water retention curves and Ksat were determined using pressure cells and the constant head method, respectively. Tillage reduced ρb to 0.94 g cm−3. Changes in ρb increased with depth, reaching a ρb of 1.11 g cm−3 in the 0–5 cm layer, and a ρb of 1.42 g cm−3 at the deepest tilled layer. Soil water retention curves were markedly steeper for samples with higher ρb, indicating an overall increase in water retained at a soil matric potential (Ψ) of −33 kPa. Evaluation of two modeling approaches for water retention as a function ρb indicated that changes in water retention with increases in ρb could be reasonably estimated if a matching point was used. No clear relationship between Ksat and ρb was obvious for ρb < 1.06 cm3 cm−3, but for ρb > 1.06 cm3 cm−3, Ksat decreased markedly (order of magnitude) as ρb increased. Hydraulic properties varied strongly depending on time since tillage and soil depth, and results have implications for models of tilled soils, as well as for studies comparing tilled and non-tilled soils.

Integration of residual herbicides with cover crop termination in soybean

AbstractCover crops have increased in popularity in midwestern U.S. corn and soybean systems in recent years. However, little research has been conducted to evaluate how cover crops and residual herbicides are effectively integrated together for weed control in a soybean production system. Field studies were conducted in 2016 and 2017 to evaluate summer annual weed control and to determine the effect of cover crop biomass on residual herbicide reaching the soil. The herbicide treatments consisted of preplant (PP) applications of glyphosate plus 2,4-D with or without sulfentrazone plus chlorimuron at two different timings, 21 and 7 d prior to soybean planting (DPP). Cover crops evaluated included winter vetch, cereal rye, Italian ryegrass, oat, Austrian winter pea, winter wheat, and a winter vetch plus cereal rye mixture. Herbicide treatments were applied to tilled and nontilled soil without cover crop for comparison. The tillage treatment resulted in low weed biomass at all collection intervals after both application timings, which corresponded to tilled soil having the highest sulfentrazone concentration (171 ng g−1) compared with all cover crop treatments. When applied PP, herbicide treatments applied 21 DPP with sulfentrazone had greater weed (93%) and waterhemp (89%) control than when applied 7 DPP (60% and 69%, respectively). When applied POST, herbicide treatments with a residual herbicide resulted in greater weed and waterhemp control at 7 DPP (83% and 77%, respectively) than at 21 DPP (74% and 61%, respectively). Herbicide programs that included a residual herbicide had the highest soybean yields (≥3,403 kg ha−1). Results from this study indicate that residual herbicides can be effectively integrated either PP or POST in conjunction with cover crop termination applications, but termination timing and biomass accumulation will affect the amount of sulfentrazone reaching the soil.

Submicroscopy of Aggregates of Luvic Phaeozems under Different Land Uses in the Southeast of the Buenos Aires Province, Argentina

Soil aggregates are key elements of soil structure that play an important role in several soil processes. One of the major factors that affect soil structure are the anthropogenic activities. Such modifications can be studied by different scales of analysis, macro, meso and microscale; and measured through different soil properties. The aim of our work is to perform description at submicroscopic scale of the soil aggregates matrices of Luvic Phaeozems affected by the different uses in the southeastern part of Buenos Aires, Argentina. The descriptions were made taking into account: (a) characteristics of aggregates matrix, (b) elemental composition of matrix and (c) organics components (plant residues, other carbon components) and microbiogical components. In natural and forested soils, the content of organic carbon in the aggregate matrices is higher, while in cultivated soils there is a decrease, which results in a decrease in their structural stability. The observations under MEB and the EDAXs have contributed to defining the morphological characteristics of the aggregate matrices from granular porous organic ones in non-tilled soils to compact ones in cultivated plots.

Finding the Technological Sweet Spot: The Smallholder Conservation Agriculture Maize Seeder

The seeder is integral to smallholder agricultural production. This technology seeks to lessen farmer labor requirements, meter seeds accurately, and minimize excessive soil disturbance. Hand seeders play a central role in conservation agriculture (CA) for the smallholder farmer as a means to plant through residue cover and penetrate non-tilled soil surfaces. Two trials in maize (Zea mays, L.) residue and soybean (Glycine max, L.) residue were conducted to test seven seeders of increasing mechanization levels: five hand operated, one mechanized, and one tractor-drawn control. The experiment site was in Mt. Gilead, Ohio, at the Eastern end of the US “Corn Belt” that had been under continuous no-till production for seven years. Experimental conditions at the site sought to mimic smallholder conditions through seeding and hand harvesting. Seeders were evaluated based on plant population establishment, crop growth stage, crop heights and final maize grain yield. The hand seeders were further evaluated based on their economic viability and usability – key challenges to the ultimate adoption of new seeding technologies. The study found that the seeders tested performed equally to the control, the John Deere MaxEmerge Conservation planter, the crop-seeding capacity and price evaluation identified the Haraka rolling planter ill-suited for smallholders while the OSU Greenseeder proved highest qualitative performance. In conclusion, all evaluations indicate that a medium level of mechanization is appropriate and necessary to be successful in a smallholder CA system although continued research is necessary.

Effect of Vegetative Buffer Strips on Herbicide Runoff From a Nontilled Soil

Buffer strips can reduce herbicide runoff from cultivated fields due to the ability of vegetation to impede the flow of surface runoff, promote infiltration, and adsorb herbicides. Conservation agriculture has many environmental advantages, but the transition phase from a conventional to a conservation system is a critical period, especially for surface runoff. In 2015, a field in Italy that was transitioning from conventional to conservation agriculture was tested to analyze the efficacy of different types of buffer strips in reducing the runoff of three herbicides compared with no-buffer plots. At each runoff event, water volume was measured and terbuthylazine, metolachlor, and mesotrione concentrations were determined. Buffer strips were able to reduce the number of runoff events by 63% to 83%. The runoff volumes were significantly reduced in the presence of buffer strips, whereas no differences were found between different types of buffer strips. Among herbicides, mesotrione was not detected in runoff water samples. The highest losses of terbuthylazine and metolachlor were from plots without buffer strips during the first three runoff events. All types of buffer strips significantly reduced the total losses of terbuthylazine and metolachlor in the monitored runoff events, with a reduction of more than 99%. This study confirmed that buffer strips are a very effective mitigation system against surface water pollution by herbicides, even in agronomic situations that promote runoff.

Straw Production, Carbon and Ash Content Variations after Ten Cycles of Recurrent Selection in Bread Wheat Grown under Tilled and Non-tilled Soils

The objective of this work was to determine the change for straw production, carbon and ash content in vegetative tissues through ten cycles of recurrent selection in bread wheat, evaluated under tilled (CT) and non-tilled (NT) soils. Twenty-four wheat genotypes, four for each one of the 0, 2, 4, 6, 8 and 10 cycles of recurrent selection (RS), were used in this study. Experiments were established during two successive seasons. Ash content was expressed on dry mass basis. To estimate the carbon content, we based our calculation on the assumption that organic matter is 50% carbon. Straw dry weight was measured. For each trait, a linear mixed model (regression) was fitted to the experimental data. In response to the number of selection cycles, the ash content percentage increased under CT and decreased under NT. Carbon content decreases under CT, but increases under NT. The sequestered straw carbon and the straw production significantly decrease under CT meanwhile there was no change under NT. The observed increase for straw ash content would be related to the highest rate of transpiration in the more advanced recurrent selection cycles. Consistent with these results, the percentage of straw carbon content decreased because of the mobilization of reserves from the stems and leaves to the grains.

Hardpan in skeletal soils: Statistical approach to determine its depth in a cherry orchard plot

AbstractSkeletal soils are not suitable for agriculture, and often are allocated to marginal uses such as cherry orchards for timber production. These require some agricultural practices (irrigation, soil tillage or weed control) which can contribute to the development of a hardpan. Compacted layers can adversely affect timber production, so subsoiling works are required. This study examined the effect of six years of tillage on hardpan formation in a skeletal soil by means of mechanical impedance measurements with a dynamic penetrometer cone (dynamic cone test), a method that is quick and easy to use, but can suffer from interference by stones. Mechanical impedances along the soil profile were measured in four plots differing in tillage (with or without) and drip irrigation (with or without) treatments. Exploratory data analysis together with statistical inference techniques related to linear general models were applied. The presence of a transitional layer on top of the hardpan is suggested in the non-tilled plot and soil depth that can be explored easily by roots has increased by 20 cm.

Nitrogen management for zero till wheat with surface retention of rice residues in north-west India

In intensive rice–wheat systems of north-west (NW) India, surface retention of rice residues in wheat has been recommended instead of burning. Optimum nitrogen (N) management for zero till (ZT) wheat sown into rice residues may to differ from that of conventional practice (in-situ burning of residues followed by intensive tillage prior to sowing). Therefore, we conducted several on-farm and on-station field experiments in 2007–2008 to 2012–2013 to evaluate N management practices for ZT wheat sown into rice residues using the Happy Seeder. The optimum N rate for wheat planted into rice residues in fields with no or only a short history of rice residue retention was 120kgNha−1, the current recommendation for conventional practice. Short-term (up to 20 d) soil N mineralization was lower in undisturbed soil than disturbed soil, while the total amount of N mineralization was similar after 40d, suggesting that over the crop season, total soil N mineralization may be similar in tilled and non-tilled soil. Ammonia volatilization loss from urea broadcast over the residue covered surface, followed by irrigation, was low (<2kgha−1) regardless of time of urea application. Band placement of 20% of the fertilizer N as diammonium phosphate at seeding, and topdressing of the remaining 80% as urea in two equal doses before first and second irrigations produced higher grain yield and N use efficiency than other treatments. However, surface residue retention reduces the rate of soil drying and in some situations this delays the time of the second irrigation and thus N fertilizer application beyond the optimum time. Therefore, the effect of banding various proportions of the urea N between the rows at sowing was investigated. The results showed that, on a loam soil, up to 75% of the recommended N fertilizer can be applied at sowing, 24kgNha−1 as DAP with the seed and 66kgNha−1 as urea drilled between every second wheat row, without loss of yield. In conclusion, a better applied N management strategy for ZT wheat than currently practiced is drilling of 24kgNha−1 as diammonimum phosphate into the soil at seeding followed by two top-dressings of 48kgNha−1 each just prior to first and second irrigations.

Agricultural practices indirectly influence plant productivity and ecosystem services through effects on soil biota.

It is well established that agricultural practices alter the composition and diversity of soil microbial communities. However, the impact of changing soil microbial communities on the functioning of the agroecosystems is still poorly understood. Earlier work showed that soil tillage drastically altered microbial community composition. Here we tested, using an experimental grassland (Lolium, Trifolium, Plantago) as a model system, whether soil microbial communities from conventionally tilled (CT) and non-tilled (NT) soils have different influences on plant productivity and nutrient acquisition. We specifically focus on arbuscular mycorrhizal fungi (AMF), as they are a group of beneficial soil fungi that can promote plant productivity and ecosystem functioning and are also strongly affected by tillage management. Soil microbial communities from CT and NT soils varied greatly in their effects on the grassland communities. Communities from CT soil increased overall biomass production more than soil communities from NT soil. This effect was mainly due to a significant growth promotion of Trifolium by CT microorganisms. In contrast to CT soil inoculum, NT soil inoculum increased plant phosphorus concentration and total plant P content, demonstrating that the soil microbial communities from NT fields enhance P uptake. Differences in AM fungal community composition resulting, for instance, in twofold greater hyphal length in NT soil communities when compared to CT, are the most likely explanation for the different plant responses to CT and NT soil inocula. A range of field studies have shown that plant P uptake increases when farmers change to conservation tillage or direct seeding. Our results indicate that this enhanced P uptake results from enhanced hyphal length and an altered AM fungal community. Our results further demonstrate that agricultural management practices indirectly influence ecosystem services and plant community structure through effects on soil biota.