3-year Rotation Research Articles

Economic analysis of organic cropping systems under different tillage intensities and crop rotations

AbstractCosts of production and organic price premiums are defining factors influencing the economic viability of organic crop production systems. Different agronomic practices, such as crop rotation and tillage intensity, are known to affect the economic performance of the production systems. The aim of this study was to compare the impact of two crop rotation sequences (simplified and diversified) and two levels of tillage intensity (high and low) on the cost of production, gross return and gross margin of crops when grown under organic management in the semi-arid Brown soil zone of the Canadian Prairies. The 2-year simplified rotation sequence consisted of forage pea (Pisum sativum L.) grown as a green manure followed by hard red spring wheat (HRSW) (Triticum aestivum L.), while the 4-year diversified rotation sequence was forage pea green manure followed by flax (Linum usitatissimum L.) or yellow mustard (Sinapis alba L.), field pea or lentil (Lens culinaris L.) and HRSW. Our hypothesis that a more diversified crop rotation would increase profitability over a traditional simplified crop rotation was supported by the findings. However, the findings did not support our hypothesis that reducing tillage intensity, and the combination of tillage reduction and diversified crop rotation through a synergetic response, would further enhance profitability. Analysis of the breakeven prices and breakeven yields for crops indicated the importance of adopting diversified crop rotations and choosing crops with high organic price premiums as means to maximize the long-term profitability of organic cropping systems.

Leptosphaeria maculans Isolates Reveal Their Allele Frequency in Western Canada.

Blackleg, caused by Leptosphaeria maculans, is a major disease of canola in Canada, Australia, and Europe. For effective deployment of resistant varieties and disease management, it is crucial to understand the population structure of L. maculans. In this study, we analyzed L. maculans isolates from commercial fields in western Canada from 2014 to 2016 for the presence and frequency of avirulence (Avr) genes. A total of 1,584 isolates were examined for the presence of Avr genes AvrLm1, AvrLm2, AvrLm3, AvrLm4, AvrLm6, AvrLm7, AvrLm9, AvrLepR1, AvrLepR2, and AvrLmS via a set of differential host genotypes carrying known resistance genes and a PCR assay. Several Avr genes showed a higher frequency in the pathogen population, such as AvrLm6 and AvrLm7, which were present in >90% of isolates, whereas AvrLm3, AvrLm9, and AvrLepR2 showed frequencies of <10%. A total of 189 races (different combinations of Avr genes) were detected, with Avr-2-4-6-7-S, Avr-1-4-6-7, and Avr-2-4-6-7 as the three predominant races. When the effect of crop rotation was assessed, only a 3-year rotation showed a significantly higher frequency of AvrLm2 relative to shorter rotations. This study provides the information for producers to select effective canola varieties for blackleg management and for breeders to deploy new R genes in disease resistance breeding in western Canada.

Temporal Soil Bacterial Community Responses to Cropping Systems and Crop Identity in Dryland Agroecosystems of the Northern Great Plains

Industrialized agriculture results in simplified landscapes where many of the regulatory ecosystem functions driven by soil biological and physicochemical characteristics have been hampered or replaced with intensive, synthetic inputs. To restore long-term agricultural sustainability and soil health, soil should function as both a resource and a complex ecosystem. In this study, we examined how cropping systems impact soil bacterial community diversity and composition, important indicators of soil ecosystem health. Soils from a representative cropping system in the semi-arid Northern Great Plains were collected in June and August of 2017 from the final phase of a 5-year crop rotation managed either with chemical inputs and no-tillage, as a USDA-certified organic tillage system, or as a USDA-certified organic sheep grazing system with reduced tillage intensity. DNA was extracted and sequenced for bacteria community analysis via 16S rRNA gene sequencing. Bacterial richness and diversity decreased in all farming systems from June to August and was lowest in the chemical no-tillage system, while evenness increased over the sampling period. Crop species identity did not affect bacterial richness, diversity, or evenness. Conventional no-till, organic tilled, and organic grazed management systems resulted in dissimilar microbial communities. Overall, cropping systems and seasonal changes had a greater effect on microbial community structure and diversity than crop identity. Future research should assess how the rhizobiome responds to the specific phases of a crop rotation, as differences in bulk soil microbial communities by crop identity were not detectable.

Techno-Economic Viability of Agro-Photovoltaic Irrigated Arable Lands in the EU-Med Region: A Case-Study in Southwestern Spain

Solar photovoltaic (PV) energy is positioned to play a major role in the electricity generation mix of Mediterranean countries. Nonetheless, substantial increase in ground-mounted PV installed capacity could lead to competition with the agricultural use of land. A way to avert the peril is the electricity-food dual use of land or agro-photovoltaics (APV). Here, the profitability of a hypothetical APV system deployed on irrigated arable lands of southwestern Spain is analyzed. The basic generator design, comprised of fixed-tilt opaque monofacial PV modules on a 5 m ground-clearance substructure, featured 555.5 kWp/ha. Two APV shed orientations, due south and due southwest, were compared. Two 4-year annual-crop rotations, cultivated beneath the heightened PV modules and with each rotation spanning 24 ha, were studied. One crop rotation was headed by early potato, while the other was headed by processing tomato. All 9 crops involved fulfilled the two-fold condition of being usually cultivated in the area and compatible with APV shed intermitent shading. Crop revenues under the partial shading of PV modules were derived from official average yields in the area, through the use of two alternative sets of coefficients generated for low and high crop-yield shade-induced penalty. Likewise, two irrigation water sources, surface and underground, were compared. Crop total production costs, PV system investment and operating costs and revenues from the sale of electricity, were calculated. The internal rates of return (IRRs) obtained ranged from a minimum of 3.8% for the combination of southwest orientation, early-potato rotation, groundwater and high shade-induced crop-yield penalty, to a maximum of 5.6% for the combination of south orientation, processing-tomato rotation, surface water and low shade-induced crop-yield penalty.

Impact of logging on the biodiversity and composition of flora and fauna in the mangrove forests of Bintuni Bay, West Papua, Indonesia

The mangrove ecosystem of Bintuni Bay, West Papua, Indonesia is one of the largest in the world covering more than 250,000 ha. In the southern part of the bay, ± 82,120 ha of mangroves and surrounding area is managed and harvested under a 30-year rotation cycle to produce wood chips, with strict compliance to sustainable forest management standards. Flora and fauna have been continuously monitored for a period of 10 years (2009–2018), to assess the effectiveness of environmental management programs on the biological aspect. Mangrove flora and fauna recorded in the area comprise 28 true mangrove species representing 11 families along with 103 birds (40 families), 9 reptiles (6 families) and 7 mammals (5 families). Results confirm previous studies that secondary mangrove forest shows significant growth and recovery, with 5 true mangrove species consistently becoming dominant species in primary and secondary mangrove forest. Logging on mangroves significantly impacted the biodiversity of flora as Rhizopora apiculata become more dominant in secondary forest covering 69% of total species composition. Abundance and diversity of fauna in secondary forest was higher in younger forests as compared to older stands. About 18% of total fauna individual was categorized as keystone species. Fauna composition was not significantly impacted by logging most likely due to the abundance of habitat (untouched forest) remaining in the surrounding harvest area. With appropriate environmental management programs, impact of logging on mangrove forest can be minimized and the ecosystem could be restored effectively to provide adequate habitat for flora and fauna.

Yield and biomass quality of shrub willow hybrids in differing rotation lengths and spacing designs

To study the effects of planting design and harvest rotation on shrub willow bioenergy crops, 10 shrub willow genotypes were established in 2009 in side-by-side randomized complete block trials, one with a double-row design and the other a single-row design. Both double-row and single-row designs were established with the same stand density, ~14,000 plants ha−1. The single-row design was harvested four times on a 2-year rotation from 2009 to 2017. The double-row plots were harvested twice on a 4-year rotation. Biomass yield, growth parameters, wood composition, specific gravity, and calorific values were evaluated. Mean annualized yield over 8 years from the single-row design was 9.98 Mg ha−1 yr−1 whereas mean annualized yield for the double-row spacing design was 9.32 dry Mg ha−1 yr−1. Cumulative biomass production averaged across all genotypes from four biennial, single-row harvests resulted in 79.9 Mg ha−1 compared with two quadrennial double-row harvests of 74.5 Mg ha−1. A triploid hybrid, LA970253, produced the greatest mean annual yield in the single-row design of 14.0 dry Mg ha−1 yr−1, followed by another triploid, ‘Fabius’, which had the greatest yield in the double-row design of 12.5 dry Mg ha−1 yr−1. In both planting designs, hemicellulose and cellulose content increased over time, while lignin and ash content decreased. Calorific values ranged from 17.62 to 19.02 MJ kg−1 with no significant differences between designs or genotypes. The results from this study suggest that some genotypes respond better to shorter rotations, but over multiple rotations there is no difference in total yield.

Russian thistle (Salsola tragus L.) control with soil-active herbicides in no-till fallow

AbstractThe benefits of no-till fallow, which include reduced soil erosion, improved soil health, and increased stored soil water, are in jeopardy because of the widespread development of glyphosate resistance in Russian thistle. The objective of this research was to evaluate the efficacy of soil-active, residual herbicides for Russian thistle control in no-till fallow. The combinations of sulfentrazone + carfentrazone and flumioxazin + pyroxasulfone, and metribuzin alone were each applied in late fall, late winter, and split-applied in late fall and late winter at three sites: Adams, OR, in 2017–2018; Lind, WA, in 2018–2019; and Ralston, WA, in 2019–2020. All treatments provided good to excellent control of the initial flush of Russian thistle when assessed in mid-May, except the late-fall application of metribuzin at all three sites, and the late-fall application of sulfentrazone + carfentrazone at Adams. Cumulative Russian thistle densities, evaluated monthly throughout the fallow season, were lowest for the sulfentrazone + carfentrazone treatments, except for the late-fall application at Adams. However, flumioxazin + pyroxasulfone and metribuzin provided greater control of tumble mustard and prickly lettuce than did sulfentrazone + carfentazone. Sulfentrazone + carfentrazone, flumioxazin + pyroxasulfone, and metribuzin can all be used for Russian thistle control in fallow. To reduce the risk for crop injury to subsequently planted winter wheat, a late-fall application of sulfentrazone + carfentrazone may be the preferred treatment in low-rainfall regions where winter wheat–fallow is commonly practiced. A late-winter application may be preferred in higher rainfall regions where a 3-year rotation (e.g., winter wheat–spring wheat–fallow) is common. Flumioxazin + pyroxasulfone should be considered if other broadleaf weeds, such as tumble mustard or prickly lettuce, are of concern. The use of these soil-applied herbicides will reduce the need for the frequent application of glyphosate for Russian thistle control in no-till fallow.

Survival of Xanthomonas cucurbitae in Different Crop Rotations, Plant Debris, and Weeds in Pumpkin Fields

This study was conducted to evaluate the effectiveness of crop rotation in managing Xanthomonas cucurbitae, the causal agent of Xanthomonas leaf spot, in pumpkin fields. The study was conducted using ‘Howden’ pumpkin, a susceptible pumpkin cultivar, at four sites with no history of cucurbit production. All sites were planted with pumpkins in the first year of crop rotations. The disease developed at all four sites. In a 3-year rotation with nonhost crops, the severity of Xanthomonas leaf spot in pumpkin plots was significantly (P &lt; 0.05) lower than those of plots in the 2-year rotation with nonhost crops and continuous pumpkin production. Furthermore, X. cucurbitae was recovered from pumpkin plant debris 15 months after harvesting pumpkins in commercial fields, and the pathogen was viable. X. cucurbitae was also isolated from asymptomatic weeds in pumpkin fields. In a greenhouse inoculation of weeds with X. cucurbitae, however, Xanthomonas leaf spot developed only on leaves of burcucumber (Sicyos angulatus) and velvetleaf (Abutilon theophrasti) weeds. In the infested soil with X. cucurbitae, the bacterium was not recovered after 15, 42, and 56 days at 22, 12, and 4°C, respectively. The results showed that crop rotation alone does not provide adequate protection of pumpkin plants against X. cucurbitae.

RESEARCH REGARDING THE EFFICIENCY OF SOYBEAN CULTIVATION IN DIFFERENT TILLAGE SYSTEMS AND THEIR INFLUENCE ON SOIL COMPACTION, ACCUMULATION AND WATER STORAGE

In the last years there has been a slight increase in average annual temperatures, as well as a high fluctuation in the distribution of rainfall, thus the reduction of the effects of atmospheric and pedological drought is part of the reasons that determine the orientation towards new variants of soil tillage. The experiment conceived and performed at ARDS Turda includes four variants of soil tillage: plow with the turn of the furrow (CS), chisel (MT), disk (MD) and no tillage (NT), in a 3-year crop rotation of soybean - winter wheat - maize. The momentary water reserve was higher in the MD and NT system compared to the CS, MT. The specific resistance of the soil to penetration (Rp) in NT, MD are higher compared to the CS and MT systems. Soybeans can be cultivated in a MT, the yield difference compared to the CS is 107 kg/ha. Compared to CS (66.5 L/ha) significant reductions of diesel consumption are made in the MD system (21 L/ha) and in the NT (31.7 L/ha).

Improving effects of vertebral column manipulator on lower instrumented vertebrate tilt and lumbar mobility of lenke 5C patients for follow-up of minimum 2 years

ObjectiveTo compare the lower instrumented vertebra (LIV) related parameters and lumbar function in the long-term follow-up of Lenke 5C adolescent idiopathic scoliosis patients treated with vertebrate column manipulator (VCM) or simple rod derotation (SRD) maneuver. Methods43 Lenke 5C patients treated with VCM or SRD maneuver were retrospectively enrolled without randomization. The clinical and radiographic data were completely documented. Thorough comparisons of relevant variables were performed at three different time points (preoperative, immediately postoperative, 2-year follow-up) between the two groups. ResultsThe curvatures of all patients were satisfactorily corrected with good sagittal achieved. No severe postoperative complications occurred. The postoperative LIV rotation of VCM group was significantly smaller than SRD group (7.12° ± 4.16° vs 11.64° ± 5.40°, P < 0.01). The LIV-tilt of VCM group were significantly better improved immediately after surgery (5.58° ± 3.60° vs 7.96° ± 5.89°, P = 0.021) and at 2-year follow-up (4.78° ± 3.11° vs 8.59° ± 5.51°, P < 0.01). Meanwhile, there was a spontaneous improvement of postoperative LIV-tilt in VCM group but an aggravation in SRD group. The relevant parameters that correlated with LIV-tilt were postoperative LIV rotation (r2 = 0.336, P < 0.001), 2-year LIV rotation (r2 = 0.410, P < 0.001) and 2-year coronal imbalance (r2 = 0.282, P < 0.001). In addition, VCM group conserved more lumbar mobility (46.90° ± 17.34° vs 30.91° ± 14.27°, P < 0.01). ConclusionsVCM system on Lenke 5C patients could improve the LIV rotation, LIV-tilt and the risk of trunk decompensation and distal adding-on more efficaciously than SRD maneuver in follow-up, as well as conserving more lumbar mobility.

Medical Education Reform in China: The Shanghai Medical Training Model.

Medical Education Reform in China: The Shanghai Medical Training Model.

Decline in Soil Microbial Abundance When Camelina Introduced Into a Monoculture Wheat System.

Camelina [Camelina sativa (L.) Crantz] of the Brassicaceae family is a potential alternative and oilseed biofuel crop for wheat (Triticum aestivum L.)-based cropping systems of the Inland Pacific Northwest (PNW) of the United States. We investigated the effect of this relatively new rotational crop on soil microbial communities. An 8-year cropping systems experiment was initiated in 2007 at Lind, WA, to compare a 3-year rotation of winter wheat (WW)-camelina (C)-fallow (F) to the typical 2-year WW-F rotation. All phases of both rotations (total = 20 plots) were present every year to allow valid statistical analysis and data interpretations. Monoculture WW-F is the dominant system practiced by the vast majority of farmers on 1.56 million ha of cropland in the PNW drylands that receive <300 mm average annual precipitation. Microbial abundance and community composition were determined using phospholipid fatty acid analysis (PLFA) from soil samples collected during 3 consecutive years beginning in 2010. The abundance of fungi, mycorrhizae, Gram positive and negative bacteria, and total microbial abundance all declined over the 3-year period in the WW-C-F rotation compared to the WW-F rotation. All microbial lipid biomarkers were significantly less in fallow compared to WW of the WW-C-F rotation. The 2-year WW-F rotation demonstrated few differences in microbial lipid abundance and community structure between the rotation phases. Microbial abundance declined and community structure shifted in the 3-year WW-C-F rotation likely due to the combination of a Brassica crop followed by a 13-month-long fallow. The results of this study suggest that camelina in combination with a fallow period may disrupt microbial communities that have become stable under historical WW-F monocropping. Such disturbances have the potential to affect soil processes that have been provided by wheat-adapted microbial communities. However, the disruption appears to be short-lived with the microbial abundance of WW in the WW-C-F rotation, returning to similar levels observed in the WW-F rotation.

Winter Triticale: A Long-Term Cropping Systems Experiment in a Dry Mediterranean Climate

Triticale (X Triticosecale Wittmack) is a cereal feed grain grown annually worldwide on 4.2 million ha. Washington is the leading state for rainfed (i.e., non-irrigated) triticale production in the USA. A 9-year dryland cropping systems project was conducted from 2011 to 2019 near Ritzville, WA to compare winter triticale (WT) with winter wheat (Triticum aestivum L.) (WW) grown in (i) a 3-year rotation of WT-spring wheat (SW) -no-till summer fallow (NTF) (ii) a 3-year rotation of WW-SW-undercutter tillage summer fallow (UTF) and (iii) a 2-year WW-UTF rotation, We measured grain yield, grain yield components, straw production, soil water dynamics, and effect on the subsequent SW wheat crop (in the two 3-year rotations). Enterprise budgets were constructed to evaluate the production costs and profitability. Grain yields averaged over the years were 5816, 5087, and 4689 kg/ha for WT, 3-year WW, and 2-year WW, respectively (p &lt; 0.001). Winter triticale used slightly less water than WW (p = 0.019). Contrary to numerous reports in the literature, WT never produced more straw dry biomass than WW. Winter wheat produced many more stems than WT (p &lt; 0.001), but this was compensated by individual stem weight of WT being 60% heavier than that of WW (p &lt; 0.001). Spring wheat yield averaged 2451 vs. 2322 kg/ha after WT and WW, respectively (p = 0.022). The market price for triticale grain was always lower than that for wheat. Winter triticale produced an average of 14 and 24% more grain than 3-year and 2-year WW, respectively, provided foliar fungal disease control, risk reduction, and other rotation benefits, but was not economically competitive with WW. A 15–21% increase in WT price or grain yield would be necessary for the WT rotation to be as profitable as the 3-year and 2-year WW rotations, respectively.

Expected carbon emissions from a rubber plantation in Central Africa

The development of agriculture on degraded lands is increasingly seen as a strategy to boost food availability and economic productivity while minimizing environmental degradation and loss of forests. To understand the effects of agricultural production on forest carbon, we quantify the aboveground carbon (AGC) of a degraded forest in northeast Gabon (the Olam Rubber Gabon concession) designated for development to a rubber plantation. Combining field measurements from 19 1-ha tree plots and aerial LiDAR, we estimate forest AGC stocks and emissions under four development scenarios: no development, 30-year rubber rotation, extended rubber rotation (replanting of plantation in stages at 30 and 40 years), and 30-year oil palm rotation. On average, the degraded forest in the study area stored 123.8 Mg C ha−1, a mean AGC lower than the Gabon average (141.6 Mg C ha−1) but substantially higher than the 75 Mg C ha−1 threshold recommended by the High Carbon Stock protocol. Converting secondary forest to plantation might incur high environmental opportunity costs from lost carbon sequestration through forest succession and growth. In this study, we estimate that a rubber plantation can sequester similar amounts of AGC as secondary forest by the end of a 30-year rotation; however, the time-averaged AGC of regenerating secondary forests under no development would be 184% higher than a mature rubber plantation with a 30-year rotation, 169% higher than an extended rubber rotation, and 512% higher than a 30-year oil palm rotation. When degraded forest is developed for agriculture, measures should be taken to avoid emissions and prolong carbon retention. We specifically estimate carbon retention from extended harvest rotations and conserving high carbon value areas as set-asides and highlight recommendations from the literature such as minimizing soil disturbance and creating rubber timber products (e.g. furniture). To minimize carbon emissions from agriculture, crop plantation area should be minimized at national and regional scales in highly forested countries, and new plantations should be coupled explicitly with effective forest restoration actions, through suitable regulation and planning, to mitigate or compensate for their climate and biodiversity impacts.

Future crop tree release treatments in neotropical forests – an empirical study on the sensitivity of the economic profitability

Silvicultural treatments are a common tool for increasing commercial timber production. Their impact on the growth or mortality of the remaining stand is well researched. This study focuses on the economic aspects of silvicultural treatments in neotropical forests. We have selected liberation treatments and consider them to be investments that are expected to pay for themselves through the additional growth of released trees and corresponding timber prices following a 30-year rotation period. The study is based on empirical data collected on experimental sites of 10 km2 in Belize, Guyana, Suriname, Trinidad and Tobago. To determine the timber price or additional growth required to cover the treatment costs, we used a reverse approach based on net present values. The treatment costs range between US$4.5 and US$8.9 per released tree. The additional growth required per released tree to cover the expenses for silvicultural treatments depends on treatment costs and achievable timber prices and varies from 0.02 to 3.5 m3. Conversely, if a potential increase in growth is assumed, timber prices must be between 34 and 578 US$ m-3 to at least cover the cost of treatments. We found a high sensitivity of profitability related to the additional growth, the timber prices to be achieved, and the discount rate chosen, which significantly increases the financial risk of silvicultural treatments as an investment tool. The decision whether to use silvicultural treatments or not is often solely guided by the expected improvement in tree growth. We, however, show that growth alone is insufficient as a decision criterion. While treatment costs are known when the decision to implement the measures is made, future timber prices and harvesting costs as well as the additional growth actually achieved are subject to uncertainties. These uncertainties have a decisive influence on the economic risk assessment, which is reflected in the choice of the internal interest rate. Our study demonstrates that investments in silvicultural treatments involve a considerable financial risk and that the decision to carry out silvicultural treatments should always be the subject of a thorough investment calculation.

Returns to Vietnamese smallholder farmers from managing acacia plantations for sawn wood over 4-10 year rotations

Since 1990, forest area in Vietnam has increased by around 15%, and now comprises more than 42%. The increase is mainly due to the establishment of short rotation Acacia plantations, which assist in the rehabilitation of under-utilised lands, and can be grown in short rotations by smallholder farmers for a range of uses. Presently, a high demand for woodchips encourages farmers to maintain short rotations for pulplogs and provides them with a relatively quick return from their forestry land. The Vietnamese Government has recognised an opportunity to increase sawlog production for a rapidly expanding furniture industry. The main objective of this study was to understand if small-scale Acacia plantations, managed for both pulp- and sawlog production, could provide an attractive return to smallholder farmers. Forecast earnings from the models indicated that opportunities exist for smallholders to improve their financial returns. With minimal additional inputs, plantations with a thinning intervention treatment at 3-years would be more profitable than unthinned ones, irrespective of whether the plantations were harvested in year 4 through to year 8. In 4 to 8-year rotations, the 6-year thinned operation was modelled as being the most profitable. When plantation models were extended to 10-years, the returns were even higher because of the greater volume of larger diameter higher value sawlogs. Sensitivity modelling found shorter rotation returns were highly sensitive to factors influencing income, whereas 10-year rotations were shown to be more resilient, although the growers would need to manage their risk profile, as well as acquire the knowledge and management skills required to effectively manage longer rotations. Outcomes from the study suggest that growing for sawlogs is a better option for farmers, in terms of the internal rate of return. A transition from short to longer rotations will require support for farmers, in terms of: (1) risk management, (2) training in longer rotation management, and (3) greater social acceptance of longer rotations.

Long-term impact of grain legumes and nutrient management practices on soil microbial activity and biochemical properties

ABSTRACT Sustainability of rice-wheat rotation is questioned with soil degradation and depleting natural resources. The study aimed to assess the long-term impact of four crop rotations [rice-wheat, rice-wheat-mungbean, rice-chickpea, rice-wheat-rice-chickpea (2-year rotation)], each consisted of three nutrient treatments [control, integrated nutrient management (INM), and chemical fertilizers (RDF)] on soil carbon pools, soil microbial, and biochemical properties. Mungbean inclusion in rice-wheat rotation increased soil organic carbon (SOC) and microbial biomass carbon (MBC) by 17% and 27%. Rice-wheat-mungbean rotation increased soil enzymes activities over rice-wheat rotation, prominent on arylsulfatase (41%), dehydrogenase (38%), and phosphatases (32%). Rice-chickpea rotation had higher alkaline phosphatase (10%), β-glucosidase (13%), and protease (6%) activities over rice-wheat rotation. Rice-wheat-mungbean rotation increased the MBC/SOC and reduced MBC/MBN ratio over rice-wheat rotation, which indicates increased lability of soil carbon and enhanced nitrogen cycling rate. The INM treatment increased SOC (20%), MBC (53%), soil respiration (9%), and enzymes activities over RDF treatment, which was primarily attributed to higher organic matter input through farmyard manure and residues recycling. The higher SOC and microbial activity in legume-inclusive rotations influenced the base-crop (rice) productivity. Thus, the inclusion of grain legume and INM could improve microbial activity and biochemical functions in tropical rice soils.

Soil quality indicators as influenced by 5-year diversified and monoculture cropping systems

AbstractIncreasing crop diversity has been highly recommended because of its environmental and economic benefits. However, the impacts of crop diversity on soil properties are not well documented. Thus, the present study was conducted to assess the impacts of crop diversity on selected soil quality indicators. The cropping systems investigated here included wheat (Triticum aestivumL.) grown continuously for 5 years as mono-cropping (MC), and a 5-year cropping sequence [(wheat–cover crop (CC)–corn (Zea maysL.)–pea (Pisum sativumL.) and barley (Hordeum vulgareL.)–sunflower (Helianthus annuus L.)]. Each crop was present every year. This study was conducted in the northern Great Plains of North America, and soil quality data were collected for 2016 and 2017. Selected soil quality indicators that include: soil pH, organic carbon (SOC), cold water-extractable C (CWC) and N (CWN), hot water-extractable C (HWC) and N (HWN), microbial biomass carbon (MBC), bulk density (BD), water retention (SWR), wet soil aggregate stability (WAS), and urease andβ-glucoside enzyme activity were measured after the completion of 5-year rotation cycle and the following year. Crop diversity did not affect soil pH, CWC, CWN, HWC, HWN and SWR. Cropping systems that contained CC increased SOC at shallow depths compared to the systems that did not have CC. Crop diversity increased WAS, MBC, and urease andβ-glucoside enzyme activity compared with the MC. Comparison of electrical conductivity (EC) measured in this study to the baseline values at the research site prior to the establishment of treatments revealed that crop rotation decreased EC over time. Results indicate that crop diversity can improve soil quality, thus promoting sustainable agriculture.

Expression of N-cycling genes of root microbiomes provides insights for sustaining oilseed crop production.

Agricultural production is dependent on inputs of nitrogen (N) whose cycle relies on soil and crop microbiomes. Crop diversification has increased productivity; however, its impact on the expression of microbial genes involved in N-cycling pathways remains unknown. Here, we assessed N-cycling gene expression patterns in the root and rhizosphere microbiomes of five oilseed crops as influenced by three 2-year crop rotations. The first phase consisted of fallow, lentil or wheat, and the second phase consisted of one of five oilseed crops. Expression of bacterial amoA, nirK and nirS genes showed that the microbiome of Ethiopian mustard had the lowest and that of camelina the highest potential for N loss. A preceding rotation phase of lentil significantly increased the expression of nifH gene by 23% compared with wheat and improved nxrA gene expression by 51% with chemical fallow in the following oilseed crops respectively. Lentil substantially increased biological N2 fixation and reduced denitrification in the following oilseed crops. Our results also revealed that most N-cycling gene transcripts are more abundant in the microbiomes associated with roots than with the rhizosphere. The outcome of our investigation brings a new level of understanding on how crop diversification and rotation sequences are related to N-cycling in annual cropping systems.

Supporting Beneficial Insects for Agricultural Sustainability: The Role of Livestock-Integrated Organic and Cover Cropping to Enhance Ground Beetle (Carabidae) Communities

Ground beetles (Carabidae) are beneficial insects providing ecosystem services by regulating insect pests and weed seeds. Despite several studies conducted on ground beetles worldwide, there is a lack of knowledge on how these insects are affected by differently managed organic systems (e.g., tillage-based versus grazed-based) compared to that of chemical-based no-tillage conventional cropping systems. In a 5-year (2013–2017) study, we assessed the ground beetle communities in cover crops and winter wheat (Triticum aestivium L.) in Montana, USA, with three contrasting cropping systems: a chemically managed no-tillage, a tillage-based organic, and a livestock-integrated organic with reduced tillage. The first three years (i.e., 2013–2015) corresponded to the transition to organic period, while the last two (i.e., 2016–2017) were conducted in United States Department of Agriculture (USDA) organic-certified tillage-based and livestock-integrated organic systems. The experiment was designed with three management systems across three blocks as the whole plot variable and 5-year rotation of crop phases as the subplot variable. Using pitfall traps, we sampled ground beetles across all cover crop and winter wheat subplots for five years (n = 450). The data were analyzed using mixed effects models and PERMANOVA and visualized with non-metric multidimensional scaling ordination. Our study indicated that organically managed farms, whether tilled or grazed, enhance activity density, species richness, diversity, and evenness of ground beetles in the dryland row crop productions. Also, irrespective of farming system, cover crops supported higher species richness, diversity, and evenness of ground beetles than winter wheat. The ground beetle communities were mostly similar during the transition to organic period. However, during the established organic phase, cropping systems acted as contrasting ecological filters and beetle communities became dissimilar. Cover cropping affected ground beetle communities positively not only in organically managed systems but also in chemical-based conventional systems. Our study provides evidence supporting the adoption of ecologically-based cropping systems such as crop-livestock integration, organic farming, and cover cropping to enhance beneficial insects and their pest-regulation services.