Organic Crop Rotation Research Articles

Different leguminous pre-crops increased yield of succeeding cereals in two consecutive years

ABSTRACTLeguminous pre-crops are an important source of green manure in organic crop rotations for improving soil fertility and achieving high yields of cereals. We aimed to study the potential of various leguminous species, other than the traditionally cultivated red clover (Trifolium pratense L.), as green manure pre-crops for subsequent cereals. The use of different legume species enables to exploit advantages of specific legumes in organic cereal production. In order to test the legumes as pre-crops for cereals, we carried out trials located in the temperate climate zone of northeast Europe (58°44′59.41″ N, 26°24′54.02″ E). We sowed the following perennial legumes as pre-crops: red clover, alsike clover (Trifolium hybridum L.) and Washington lupine (Lupinus polyphyllus Lindl.), biennial white sweet clover (Melilotus albus Medik.) and annual Alexandria clover (Trifolium alexandrinum L.), and crimson clover (Trifolium incarnatum L.). Timothy (Phleum pratense L.) was used as a control. The leguminous pre-crops were followed by three spring cereals (barley, oat and spring wheat) and two winter cereals (rye and winter wheat). We tested the first-year after-effect (all cereals) and second-year after-effect (only barley and oat) of pre-crops on the grain yield of cereals. Perennial and biennial legume species produced the highest dry matter yield and contained the highest amount of nutrients, especially nitrogen, compared to annual species. All subsequent cereals produced significant extra yields after each leguminous pre-crop in the following two years, although the effect was smaller in the second year. The most suitable pre-crops for spring cereals were red and alsike clover followed by lupine, whereas the best pre-crops for winter cereals were sweet clover and annual clovers. Our results show the potential of various leguminous pre-crop species as valuable sources of green manure in organic crop rotation.

Indigenous practices of environmental sustainability in the Tonga community of southern Zambia.

Culture plays a significant role in conserving the environment. The purpose of this study was to explore the measures that have been employed by the Tonga people of southern Zambia to sustain their local biophysical environment. The research focussed on investigating the strategies which they use to conserve the soil, water, animals, medicinal and fruit plants, and rangeland. A qualitative research design was used in the study. The data were collected through interviews with elderly Tonga people and herbalists, and through observation and personal participation in the daily life of the Tongas. The study reveals that selective harvesting, totemism and taboos, organic farming, crop rotation and intercropping, sacredness of water sources and traditional authority are the main instruments of environmental conservation amongst the Tonga. The article concludes that governments, policymakers and environmentalists need to give the conservation strategies employed by indigenous people the prominence they deserve for environmental sustainability.

Occasional reduced tillage in organic farming can promote earthworm performance and resource efficiency

Reduced tillage has several advantages over conventional tillage (CT), including the promotion of earthworm communities and the reduction of input of energy and labour. However, its application in organic farming is mainly hindered through increasing weed pressure. One way to counteract this drawback might be to introduce occasional reduced tillage (ORT), which means applying methods of reduced tillage only in combination with selected crops. Against this background we hypothesized that (i) ORT rapidly promotes biomass, abundance and species richness of earthworm communities and that (ii) ORT generates a financial surplus for farmers. Therefore, a field experiment was established for triticale (x Triticosecale) cultivation on loamy soils in Northern Germany. The influence of tillage regimes on earthworms was investigated in a non-randomized design with n=3 fields for the ORT and CT treatment. Earthworm biomass, abundance and species richness were investigated in October 2012 and in April and October 2013. Yields were determined for the three fields under each tillage system, each field with four non-randomized replicates, before harvest in 2013. The ORT treatment consisted of two to three tillage operations prior to seeding with a maximal cultivation depth of 15cm and without ploughing, whereas the CT treatment consisted of a ploughing depth of 25–30cm and one to four other steps for seedbed preparation prior to seeding. In total, seven earthworm species were identified. Our data revealed that earthworm biomass was significantly reduced under CT, both four weeks and about seven months after tillage. This effect holds true for the number of earthworm individuals in autumn (four weeks after ploughing), but not for the number of earthworm individuals in spring (seven months after ploughing). Results of contribution margin analysis showed no consistent trend referring to tillage measures. Two fields, which performed well under CT, showed a financial surplus (+24% and +13%) when managed with ORT. At the same time one field, performing poorly under CT, generated financial deficits (-10%) under ORT. Overall ORT had immediate positive effects on earthworm populations. Furthermore, this management scheme might have positive effects on the economic outcomes of organic crop rotations if overall growing conditions are sufficient. Along with methods usually applied to investigate earthworm performance, we checked whether the number of surface casts could help estimate earthworm performance. It became apparent that the number of surface casts cannot be used as a general predictor of earthworm performance. The number of individuals of Lumbricus terrestris, the number of anecic individuals and the total earthworm biomass can be estimated the most reliable by counting surface casts.

Do green manures as winter cover crops impact the weediness and crop yield in an organic crop rotation?

The effects of different winter cover crops and their combination with composted cattle manure on weeds and crop yields were investigated within a five-field crop rotation (barley undersown with red clover, red clover, winter wheat, pea, potato) in three organic cropping systems. The control system (Org 0) followed the rotation. In organic systems Org I and Org II the winter cover crops were used as follows: ryegrass (Lolium perenne L. in 2011/2012) and a mixture of winter oilseed-rape (Brassica napus ssp. oleifera var. biennis) and winter rye (Secale cereale L.) in 2012/2013 before pea; winter oilseed rape before potato and winter rye before barley. In Org II system composted cattle manure was also applied. In comparison with the control system, the winter cover crops, depending on plant species used, reduced the biomass and density of the weeds. In both years winter rye was a better suppressor of weeds than the other winter cover crops. Cover crops increased the yield of potato in rotation crops. When used together with composted cattle manure the cover crops caused significant yield increase in cereals.

Linseed (Linum usitatissimum) as an oil crop in organic farming: abiotic impacts on seed ingredients and yield

Linseed contains substantial amounts of desired ingredients, such as omega-3 fatty acids (α-linolenic acid) and antioxidants, as well as undesired ingredients such as cyanogenic glycosides and cadmium. This paper presents and discusses the abiotic factors which influence quality and yield of linseed seeds in organic cropping systems. In temperate climates, conventional farmers can harvest more than 2.0 t seed ha−1, with oil contents ranging from 35 to 44 %. Organic trials usually had lower yields with up to approximately 1.8 t seed ha−1 in temperate, continental, and Mediterranean conditions. Cool climatic conditions in temperate regions lead to high shares (>60 %) of omega-3 fatty acids related to total oil content in organic farming as well as in conventional farming. Linseed achieved maximum yields of seeds and omega-3 fatty acids with a fertilization level of less than approximately 110 kg nitrogen ha−1. High levels of nitrogen fertilization did not benefit the content of omega-3 fatty acids; increasing the nitrogen fertilization from 52 to 260 kg ha−1 reduced the content of α-linolenic acid by 7.25 % in a trial. The content of cyanogenic compounds turned out to be positively correlated with the protein content of the seeds and the nitrogen fertilization; therefore, the usually moderate level of nitrogen supply in organic crop rotations could keep the content of cyanogenic glycosides on a comparatively low level, compared to cropping systems with higher nitrogen levels. Linseed is a hyper-accumulator of cadmium; the total cadmium content in the seeds is determined by the cadmium content of the soil and the linseed variety. Generally, the choice of linseed variety influences the quality of the seed, and respective varieties must be chosen to improve product quality. Harvest, post-harvest, and processing conditions additionally affect seed and oil quality. Heating can reduce the unwanted cyanogenic glycosides, but it also reduces the content of desired anti-oxidants and of omega-3 fatty acids.

Predicting the effect of rotation design on N, P, K balances on organic farms using the NDICEA model

AbstractThe dynamic model Nitrogen Dynamics in Crop rotations in Ecological Agriculture (NDICEA) was used to assess the nitrogen (N), phosphorus (P) and potassium (K) balance of long-term organic cropping trials and typical organic crop rotations on a range of soil types and rainfall zones in the UK. The measurements of soil N taken at each of the organic trial sites were also used to assess the performance of NDICEA. The modeled outputs compared well to recorded soil N levels, with relatively small error margins. NDICEA therefore seems to be a useful tool for UK organic farmers. The modeling of typical organic rotations has shown that positive N balances can be achieved, although negative N balances can occur under high rainfall conditions and on lighter soil types as a result of leaching. The analysis and modeling also showed that some organic cropping systems rely on imported sources of P and K to maintain an adequate balance and large deficits of both nutrients are apparent in stockless systems. Although the K deficits could be addressed through the buffering capacity of minerals, the amount available for crop uptake will depend on the type and amount of minerals present, current cropping and fertilization practices and the climatic environment. A P deficit represents a more fundamental problem for the maintenance of crop yields and the organic sector currently relies on mined sources of P which represents a fundamental conflict with the International Federation of Organic Agriculture Movements organic principles.

NDICEA Calibration and validation on a northern UK soil

Modelling nitrogen (N) dynamics in agricultural soils can improve our understanding of the nitrogen cycle in rotational systems. NDICEA (Nitrogen Dynamics in Crop rotations in Ecological Agriculture) is a tool to model soil N dynamics for maximum nitrogen use efficiency (NUE) and minimum environmental impacts from agricultural fertilization. In this study the model was calibrated using actual soil mineral N data from 2 years of a long-term organic versus conventional systems comparison trial. Calibration data was used from only the organic crop protection treatments for an organic crop rotation under (a) organic fertility management (ORG-OF) and (b) conventional fertility management (ORG-CF), and a conventional crop rotation under (c) organic fertility management (CON-OF), and (d) conventional fertility management (CON-CF). The model was subsequently validated using the same four treatment combinations from the conventional crop protection treatments. The accuracy of soil mineral N predictions was consistently improved after calibration, with the model performing best under organic fertilization regimes; reflecting the model’s original purpose. The lack of difference among treatments for the calibrated soil parameters demonstrated that the calibration procedure was robust and could result in a model that is superior to the non-calibrated one, and specific for this soil type, regardless of soil management practices. The simplification of complex biological processes into model parameters limits the use of NDICEA as a tool to explain the underlying processes driving soil N dynamics. Nevertheless it could be a useful tool for visualising field-scale N dynamics, allowing farmers and advisors to explore the impact of changing management factors on within-field N efficiency.

Soil sustainability changes in organic crop rotations with diverse crop species and the share of legumes

There have been few long-term field studies on greenhouse gases measurement in organic crop rotations under temperate climatic conditions. Little is known about the extent to which the share of legumes in a crop rotation of organic farming affects the potentials for CO2 emission and soil organic carbon sequestration. The current study was aimed to investigate soil physicochemical state and soil net CO2 exchange rate in diverse organic crop rotations with different crop species and proportions of legumes. Four 5-year duration crop rotations were investigated. The best soil sustainability of the arable layer was found in a crop rotation enriched with red clover (Trifolium pratense L.). This rotation resulted in the highest soil mesoporosity and the lowest microporosity, ensured the best supply of plant-available water and revealed high soil resistance to dry conditions. Red clover secured the highest soil organic C sequestration, caused the increase in reserves of total N and available K, and slackened the decrease of soil-available P sources. Red clover-based cropping system exhibited the highest soil net CO2 exchange rate during five experimental years. The effect of crop rotation, consisting of phacelia (Phacelia tanacetifolia Benth.), peas (Pisum sativum L.) and yellow lupin (Lupinus luteus L.), on soil sustainability was weaker than the effect of rotation with red clover. Non-legume rotations, i.e. binary (two-crop) rotation and the crop rotation involving four spring and one winter species, can be regarded as miners of soil nutrient resources rather than contributors. These rotations did not promote soil sustainability because the soil lost large amounts of macronutrients and caused 26–33% lower soil net CO2 exchange rate, compared with leguminous rotations. For future, it could be recommended for ecological farming to rely more on crop rotations with red clover to improve ecosystems functioning.

Nitrate leaching and residual effect in dairy crop rotations with grass–clover leys as influenced by sward age, grazing, cutting and fertilizer regimes

Intensive dairy farming, with grass-arable crop rotations is challenged by low N use efficiency that may have adverse environmental consequences. We investigated nitrate leaching and N fertility effects of grass–clover leys for five years in two organic crop rotations with different grassland proportions (33 and 67%) and five grassland managements in terms of cutting, grazing, fertilization and combinations thereof. In grass–clover, the combination of fertilization and grazing caused excessive leaching (average 60kg Nha−1) but leaving out either fertilization or full-time grazing substantially reduced leaching losses to on average 23kg Nha−1. There was no linear relationship between sward age and nitrate leaching. The annual N surplus of the grasslands was only weakly related to nitrate leaching (R2=0.05, P<0.01). The residual effect of grassland cultivation was highest following grazing and fertilization and lowest without fertilization or cutting-only management and was not influenced by grassland age. The arable part of the mixed crop rotation was nitrate leaky where crop coverage in autumn was insufficient. Nitrate leaching following the crops may roughly be divided into four groups: (1) low leaching (<10kg Nha−1) consisting of the barley wholecrop undersown with Italian ryegrass, (2) medium–low leaching (10–20kg Nha−1) consisting of barley with grass–clover undersown and the 1-yr-old grasslands, (3) medium leaching (25–50kg Nha−1) consisting of barley–pea and 2-4-yr-old grasslands with the 2-yr-old leaching the most (36–46kg Nha−1), and (4) high leaching (>50kg Nha−1) with lupin and maize, where especially maize was consistently high in all five years (average 81kg Nha−1). Great care should be taken during all phases of the dairy crop rotation where grasslands cause considerable build-up of fertility. With due care and the best management practice, nitrate leaching losses may be reduced to low levels.

Life cycle assessment of organic paddy rotation systems using land- and product-based indicators: a case study in Japan

This study aims to compare crop rotation systems used in organic farming (organic rotation systems) with those of both conventional farming (conventional rotation systems) and continuous rice cropping systems. Life cycle assessment (LCA) is performed based on land- and product-based indicators. Seven crop rotation systems for rice, barley, and soybeans and continuous rice production systems were evaluated in this study. These systems are practiced by farmers in the study region and were constructed using production records, statistics, and guidelines. Comparisons were then made between organic and conventional crop rotation systems and between these crop rotation systems and a continuous rice production system. We used land-oriented expression to analyze tradeoffs between physical and monetary productivity and the environmental impact per area unit and product-oriented expression to analyze efficiency as measured by the environmental impact per product unit. Results are summarized as follows: (1) The product-oriented expression, which is equivalent to conducting product LCA, revealed that organic conversion tended to be efficient, irrespective of using physical productivity (the functional unit of product mass measured as averaged annual energy yield) or using monetary productivity (the functional unit of product mass measured as averaged annual income). (2) However, the land-oriented expression revealed that there were tradeoffs between physical productivity and environmental impacts, although these tradeoffs were converted to win–win relationships if monetary productivity was used instead of physical productivity, and (3) the alteration of a continuous rice production system into crop rotations tended to be efficient and enables a win–win relationship. Organic rotation systems have the potential of being recommended as sustainable agricultural practices in comparison with conventional rotation systems and continuous (organic and conventional) rice production systems. However, it was not clarified which productivity concepts should be used as evaluation criteria. It is considered that further studies using mechanistic modeling of crop rotations are required to improve LCA practices.

Influence of Crop Rotation Fertilization System on Soil Ecology, Crop Yield and Quality of Vegetables in the South-east of Kazakhstan

The parameters of soil fertility in the 3-field short rotary grain and vegetable crop rotation were relatively high. The humus content in the control was equal to 2,07%, for versions with organic-mineral fertilizers - 2,30-2,79%. Fertilized variants of nitrogen contained 30,8-37,8 mg/kg (control - 29,4 mg/kg), potassium - 380-540 mg/kg (control - 305 mg/kg). The absorption capacity of the soil is reduced bases - 15-17mg eq./100g at baseline - 20-21 mEq./100g. Amongst the predominant cations is calcium (85-87%). The content of heavy metals in the soil within the permissible limits, however, their level increases, which can lead to contamination of soil and products. Texture of the soil has changed for the worse (fraction <0,01 mm from 43-45% to 54-57%). Improvement of soil fertility parameters can only be achieved when organic and mineral fertilizers vegetable crop rotation system. Fertilizer increased the yield of potato tubers to the control (18,7 t/ha) at 17,11-51,34%. Increase crop of onions from fertilizers to the control (28,5 t/ha) was 6,215,6 t/ha (21,75-54,74%). Harvest of sugar beet from fertilizers increased from 26,5 t/ha (control) to 31,9-42,1 t/ha. Additionally received 20,38-58,87%. Most effective on potatoes N180P180K180, onions and beets - N150P90K120. In tubers increased solids content (24,86-25,18%) and starch (16,0-17,8%). Quality bulbs and roots varied little depending on the conditions of mineral nutrition.

Modeling nitrous oxide emissions from organic and conventional cereal-based cropping systems under different management, soil and climate factors

Mitigation of greenhouse gas emissions from agriculture should be assessed across cropping systems and agroclimatic regions. In this study, we investigate the ability of the FASSET model to analyze differences in the magnitude of N2O emissions due to soil, climate and management factors in cereal-based cropping systems. Forage maize was grown in a conventional dairy system at Mabegondo (NW Spain) and wheat and barley in organic and conventional crop rotations at Foulum (NW Denmark). These two European sites represent agricultural areas with high and low to moderate emission levels, respectively. Field trials included plots with and without catch crops that were fertilized with either mineral N fertilizer, cattle slurry, pig slurry or digested manure. Non-fertilized treatments were also included. Measurements of N2O fluxes during the growing cycle of all the crops at both sites were performed with the static chamber method with more frequent measurements post-fertilization and biweekly measurements when high fluxes were not expected. All cropping systems were simulated with the FASSET version 2.5 simulation model. Cumulative soil seasonal N2O emissions were about ten-fold higher at Mabegondo than at Foulum when averaged across systems and treatments (8.99 and 0.71kgN2O-Nha−1, respectively). The average simulated cumulative soil N2O emissions were 9.03 and 1.71kgN2O-Nha−1 at Mabegondo and at Foulum, respectively. Fertilization, catch crops and cropping systems had lower influence on the seasonal soil N2O fluxes than the environmental factors. Overall, in its current version FASSET reproduced the effects of the different factors investigated on the cumulative seasonal soil N2O emissions but temporally it overestimated emissions from nitrification and denitrification on particular days when soil operations, ploughing or fertilization, took place. The errors associated with simulated daily soil N2O fluxes increased with the magnitude of the emissions. For resolving causes of differences in simulated and measured fluxes more intensive and temporally detailed measurements of N2O fluxes and soil C and N dynamics would be needed.

The Influence of Habitat Manipulations on Beneficial Ground-Dwelling Arthropods in a Southeast US Organic Cropping System.

Habitat manipulations, intentional provisioning of natural vegetation along crop edges, have been shown to enhance beneficial epigaeic invertebrate activity in many agricultural settings, but little research has been conducted on this practice in the southeast United States. We conducted a field-scale study to determine if habitat manipulations along the field edges of an organic crop rotation increase the activity-density of beneficial ground-dwelling invertebrates. Pitfall traps were used to collect micro and macro ground-dwelling organisms in nine organic crop fields (three each of maize, soybeans, and hay; 2.5-4.0 ha each) surrounded by four experimental habitat manipulations (planted native grass and prairie flowers, planted prairie flowers only, fallow vegetation, or mowed vegetation) during 2009 and 2010 in eastern North Carolina. Beneficial macro and micro invertebrates collected in these pitfall traps consisted primarily of Carabidae, Araneae, Collembola, and mite species. Results show that habitat manipulations had little effect on the activity-density of the dominant epigaeic invertebrates in our study system. Our results suggest that the activity-density of these organisms were instead determined by a combination of in-field characteristics, such as crop type, weed management practices, and within-field resources, along with the diversity of crop type in neighboring fields and the availability of other resources in the area.

Climate Change Impacts, Adaptation and Coping Strategies at Malindza, a Rural Semi-Arid Area in Swaziland

The objective of the study was to assess the impacts of climate change faced by rural households in the lowveld of Swaziland, using Malindza as a case study area, and further identify adaptation and coping strategies employed by households. A questionnaire was developed and used to conduct interviews from 160 households randomly selected in four rural communities of the study area. Data were analysed with SPSS software, and reported in forms of tables and figures. More or less all the respondents (99%) were aware of climate change and climate change variability, Sources of information included radios (92.5%), television (5.6%) and agricultural extension officers (2%). The information was however considered inadequate and of short term remedy as it was in the form of daily weather forecast. The perceived effects of climate change included crop failure (99%), loss of livestock (99%) and drying of surface water (99%). Only 9% of the households harvested enough maize to last for a year, and the rest (91%) had to rely on buying maize, exchanging it for labour or receiving food aid. The climate change adaptation strategies practiced included contour ploughing (49%), use of organic fertilisers (29%) and crop rotation (20%). Thirty two percent of the households planted hybrid maize seeds and 15% planted open pollinated maize seeds. Another 26% planted both hybrid maize and open pollinated maize seeds. On the other hand, coping strategies practiced included selling or consuming small livestock and chicken (97%), consuming maize left for seeds (93%) and reducing food intake (23%). It was clear that the effects of climate change in rural areas were severe and needed to be addressed before critical damages like loss of human life manifest. The government should ensure that farmer’s knowledge on climate change and variability is increased through education to improve their adaptive capacity.

Effects of contrasting catch crops on nitrogen availability and nitrous oxide emissions in an organic cropping system

Legume-based catch crops (LBCCs) may act as an important source of nitrogen (N) in organic crop rotations because of biological N fixation. However, the potential risk of high nitrous oxide (N2O) emissions needs to be taken into account when including LBCCs in crop rotations. Here, we report the results from a one-year field experiment, which investigated N availability and N2O emissions as affected by three LBCCs, i.e., red clover (CL), red clover–ryegrass mixture (GC) and winter vetch (WV), two non-LBCCs, i.e., perennial ryegrass (GR) and fodder radish (FR), and a control (CO) without catch crops. The effect of two catch crop management strategies was also tested: autumn harvest of the catch crop versus incorporation of whole-crop residues by spring ploughing. LBCCs accumulated 59–67kgNha−1 in their tops, significantly more than those of the non-LBCC, 32–40kgNha−1. Macro-roots accounted for >33% of total N in the catch crops. In accordance with this, LBCCs enhanced the performance of the succeeding unfertilised spring barley, thus obtaining a grain yield of 3.3–4.5Mgha−1 compared to 2.6–3.3Mgha−1 grain yield from non-LBCC and the fallow control treatments. Autumn harvest of catch crops, especially LBCCs, tended to reduce crop yield. The annual N2O emissions were comparable across treatments except for fodder radish, which had the highest N2O emission, and also the highest average yield-scaled N2O emission, at 499gN2O-NMg−1 grain. Although the sampling strategy employed in this study introduces uncertainty about the spatial and temporal variability, differences in seasonal emission patterns among catch crops were captured and harvest of catch crops in late autumn induced significantly higher emissions during winter, but lower emissions after residue incorporation in spring. In comparison with non-LBCC, LBCCs have the potential to partly replace the effect of manure application in organic cropping systems with greater crop production and less environmental footprint with respect to N2O emissions. However, harvest of the catch crops may reduce crop yield unless the harvested N is recycled as fertiliser to the crops in the rotation.

Effect of temperature and precipitation on nitrate leaching from organic cereal cropping systems in Denmark

The effect of variation in seasonal temperature and precipitation on soil water nitrate (NO3N) concentration and leaching from winter and spring cereals cropping systems was investigated over three consecutive four-year crop rotation cycles from 1997 to 2008 in an organic farming crop rotation experiment in Denmark. Three experimental sites, varying in climate and soil type from coarse sand to sandy loam, were investigated. The experiment included experimental treatments with different rotations, manure rate and cover crop, and soil nitrate concentrations was monitored using suction cups. The effects of climate, soil and management were examined in a linear mixed model, and only parameters with significant effect (P<0.05) were included in the final model. The model explained 61% and 47% of the variation in the square root transform of flow-weighted annual NO3N concentration for winter and spring cereals, respectively, and 68% and 77% of the variation in the square root transform of annual NO3N leaching for winter and spring cereals, respectively. Nitrate concentration and leaching were shown to be site specific and driven by climatic factors and crop management. There were significant effects on annual N concentration and NO3N leaching of location, rotation, previous crop and crop cover during autumn and winter. The relative effects of temperature and precipitation differed between seasons and cropping systems. A sensitivity analysis revealed that the predicted N concentration and leaching increased with increases in temperature and precipitation.

Soil microbial substrate properties and microbial community responses under irrigated organic and reduced-tillage crop and forage production systems.

Changes in soil microbiotic properties such as microbial biomass and community structure in response to alternative management systems are driven by microbial substrate quality and substrate utilization. We evaluated irrigated crop and forage production in two separate four-year experiments for differences in microbial substrate quality, microbial biomass and community structure, and microbial substrate utilization under conventional, organic, and reduced-tillage management systems. The six different management systems were imposed on fields previously under long-term, intensively tilled maize production. Soils under crop and forage production responded to conversion from monocropping to crop rotation, as well as to the three different management systems, but in different ways. Under crop production, four years of organic management resulted in the highest soil organic C (SOC) and microbial biomass concentrations, while under forage production, reduced-tillage management most effectively increased SOC and microbial biomass. There were significant increases in relative abundance of bacteria, fungi, and protozoa, with two- to 36-fold increases in biomarker phospholipid fatty acids (PLFAs). Under crop production, dissolved organic C (DOC) content was higher under organic management than under reduced-tillage and conventional management. Perennial legume crops and organic soil amendments in the organic crop rotation system apparently favored greater soil microbial substrate availability, as well as more microbial biomass compared with other management systems that had fewer legume crops in rotation and synthetic fertilizer applications. Among the forage production management systems with equivalent crop rotations, reduced-tillage management had higher microbial substrate availability and greater microbial biomass than other management systems. Combined crop rotation, tillage management, soil amendments, and legume crops in rotations considerably influenced soil microbiotic properties. More research will expand our understanding of combined effects of these alternatives on feedbacks between soil microbiotic properties and SOC accrual.

Effects of long-term organic material applications and green manure crop cultivation on soil organic carbon in rain fed area of Thailand

A long-term field experiment on organic material application and crop rotation with green manure crops has been conducted since 1976 at Lopburi Agricultural Research and Development Center, Department of Agriculture, Lop Buri Province, Thailand, to clarify the effect of organic materials and green manure crop on soil organic carbon changes. The stock change factors that stand for the relative change of soil organic carbon on the carbon stock in a reference condition (native vegetation that is not degraded or improved). Stock change factor for input of organic matter (FI), representing different levels of C input to soil such as organic material application, crop residue treatment and green manure crop cultivation, was computed with the present field experimental results. While the computed FI of "High input with manure" was within the range of IPCC default FI value, some of the computed FI of " High input without manure" was much higher than the IPCC default though it was varied due to the biomass production and nutrient contents of the green manure crops planted as the second crops after corn. Therefore, the FI computed by field experimental results can contribute to more accurate estimation of SOC changes in farm land especially in Southeast Asia because the default FI mostly depends on the experimental data in temperate zones. Moreover, the field experiment has focused the effect of reduced tillage practices on SOC changes and corn yield since 2011. The results of the experiment will be used to compute Stock change factor for management regime (FMG) which represents the effects of tillage operations.

Biogas production from catch crops: Evaluation of biomass yield and methane potential of catch crops in organic crop rotations

Manure-based biogas plants in Denmark are dependent on high yielding biomass feedstock in order to secure economically feasible operation. The aim of this study was to investigate the potential of ten different catch crop species or mixtures as feedstock for biogas production in co-digestion with manure. The biomass yield per hectare and the specific methane yield of the catch crops in two different locations, namely Holstebro and Aabenraa, were investigated. The volatile solids (VS) yield per hectare was notably influenced by the differences in climate and soil conditions between the locations, being in the ranges of 1.4–3.0 t ha−1 and 0.3–1.7 t ha−1 for Holstebro and Aabenraa, respectively. Specific methane yields were in the range of 229–450 m3 t−1 of VS. Methane yields per hectare of up to 800 m3 ha−1 were obtained, making catch crops a promising source of feedstock for manure-based biogas plants in Denmark since this biomass is not competing with food/feed production.

Sustainability and climate variability in low-input peasant maize systems in the central Mexican highlands

One of the most important challenges for agriculture is addressing high climatic variability by creating productive, resilient and adaptable systems that are highly efficient in terms of water and energy use and having the aims of neither degrading nor contaminating the environment. In Mexico, these characteristics are fulfilled by many seasonal peasant agricultural systems. Systems utilizing native seeds produce an important portion of white maize for human consumption in addition to safeguarding key agricultural genetic resources. This article evaluates the sustainability of such systems and describes the current challenges and opportunities in a representative peasant community in the watershed of Lago de Pátzcuaro in Mexico. Community farming and livestock management practices were analyzed, and ecological, economic and social indicators were measured over a two-year period. During the first year, low-input systems, which are based on the use of organic fertilizers and crop rotation, provided better results in terms of ecological indicators and equal results in terms of economic and social indicators than those achieved using a high chemical input system. In the second year, which featured early frosts and a winter drought, productivity declined in all systems; however, the most diversified systems (in terms of the maize varieties grown and the sowing of other crops) more successfully resisted these climatic adversities.