Organic Crop Rotation Research Articles

Can lead farmers reveal the adoption potential of conservation agriculture? The case of Malawi

This paper assesses the adoption potential of conservation agriculture (CA) and related technologies in Malawi, where CA appears appropriate to protect against land degradation and climate risks (droughts and floods). Estimation of adoption rates and their determinants is complicated by the relatively recent introduction of some of these technologies and limited awareness of CA principles and practices among the general population of smallholder farmers. We propose and use a lead farmer promoter-adopter approach, which relies on the promoters having had sufficient exposure and access to the technologies, their interest to adopt CA not having been distorted by excessive incentives, and them not being overly different from other smallholders in the target population. These conditions are reasonably satisfied in our application with a sample of 175 lead farmers from four districts in central and southern Malawi. Conditional on lead farmers being familiar with the technologies, we find adoption rates of 56% for organic manure and crop rotation, 26% for minimum tillage, 30% for mulching, and 12% for herbicide application. Lead farmers recommend CA and supporting agricultural practices to their followers at rates of 66% for organic manure, 49% for crop rotation, 45% for minimum tillage, 27% for mulching, and 6% for herbicide application. Assuming the validity of the promoter-adopter approach, these findings together suggest that, in central and southern Malawi, organic manure and crop rotation (in central Malawi only) have the highest adoption potential, mulching and minimum tillage come next, and herbicide application has the lowest potential. Ninety-seven percent of the lead farmers had adopted three or less of these technologies, full adoption of CA is therefore unlikely and suggest other reasons than information constraints as major impediments to its full adoption.

Effects of agricultural management practices on soil quality: A review of long-term experiments for Europe and China

In this paper we present effects of four paired agricultural management practices (organic matter (OM) addition versus no organic matter input, no-tillage (NT) versus conventional tillage, crop rotation versus monoculture, and organic agriculture versus conventional agriculture) on five key soil quality indicators, i.e., soil organic matter (SOM) content, pH, aggregate stability, earthworms (numbers) and crop yield. We have considered organic matter addition, no-tillage, crop rotation and organic agriculture as “promising practices”; no organic matter input, conventional tillage, monoculture and conventional farming were taken as the respective references or “standard practice” (baseline). Relative effects were analysed through indicator response ratio (RR) under each paired practice. For this we considered data of 30 long-term experiments collected from 13 case study sites in Europe and China as collated in the framework of the EU-China funded iSQAPER project. These were complemented with data from 42 long-term experiments across China and 402 observations of long-term trials published in the literature. Out of these, we only considered experiments covering at least five years. The results show that OM addition favourably affected all the indicators under consideration. The most favourable effect was reported on earthworm numbers, followed by yield, SOM content and soil aggregate stability. For pH, effects depended on soil type; OM input favourably affected the pH of acidic soils, whereas no clear trend was observed under NT. NT generally led to increased aggregate stability and greater SOM content in upper soil horizons. However, the magnitude of the relative effects varied, e.g. with soil texture. No-tillage practices enhanced earthworm populations, but not where herbicides or pesticides were applied to combat weeds and pests. Overall, in this review, yield slightly decreased under NT. Crop rotation had a positive effect on SOM content and yield; rotation with ley very positively influenced earthworms’ numbers. Overall, crop rotation had little impact on soil pH and aggregate stability − depending on the type of intercrop; alternatively, rotation of arable crops only resulted in adverse effects. A clear positive trend was observed for earthworm abundance under organic agriculture. Further, organic agriculture generally resulted in increased aggregate stability and greater SOM content. Overall, no clear trend was found for pH; a decrease in yield was observed under organic agriculture in this review.

Meteorological and Management Factors Influencing Weed Abundance during 18 Years of Organic Crop Rotations

AbstractOrganic crop production is often limited by the inability to control weeds. An 18-yr data set of weed cover in organic crop rotations at the long-term Farming Systems Project at Beltsville, MD, was analyzed to identify meteorological and management factors influencing weed abundance. A path analysis using structural equation models was employed to distinguish between the direct effect of factors on weed cover and the indirect effect on weed cover through effects on crop competitiveness. Grain yield of corn (Zea maysL.) and soybean [Glycine max(L.) Merr.] served as a surrogate for crop competitiveness and was found to be the most important factor influencing weed cover. Precipitation during late vegetative and early reproductive crop growth had a strong positive effect on crop yield, and thereby a negative indirect effect on weed cover, but this effect was partially offset by a positive direct effect on weed cover. Delayed crop planting date and crop rotational diversification including crops other than summer row crops had a moderate negative effect on weed cover, while having minimal effect on crop performance. Rotary hoeing also had a direct negative effect on weed cover, but a corresponding negative effect on crop performance resulted in a diminished total effect on weeds. Results demonstrate the complex interactions that define the relative abundance of weeds faced by organic growers, but, generally, factors that enhanced crop competitiveness provided the most effective weed management.

Crop yield, weed infestation and soil fertility responses to contrasted ploughing intensity and manure additions in a Mediterranean organic crop rotation

Conservation agriculture and organic farming are two alternative strategies that aim to improve soil quality and fertility in arable cropping systems through reducing tillage intensity, maintaining soil cover and increasing nutrient recycling, using farmyard and green manures. However, these practices can increase weed infestation or decrease nutrient availability. The objectives of this study were to evaluate the effects of tillage type (mouldboard vs. chisel ploughing), fertilization and green manure on soil parameters (SOC, N, bulk density, carbon stocks, and soil microbial biomass Cmic and Nmic), weed abundance and crop yields in a four-year rotation of spelt, chickpea, winter wheat and lentil in the Mediterranean region (Catalonia, Spain). Tillage and green manure did not affect crop yields or weed biomass, although during the last year of the experiment, plots with mouldboard ploughing had less weed biomass and higher lentil biomass. Fertilization was the most important factor, increasing the cereal yields, SOC, N and soil microbial biomass (Cmic and Nmic) content of the soil. However, fertilization did not favour chickpea and lentil crops because weed competition limited legume crop growth. Overall, there was a loss of SOC and a reduction of carbon stocks over the four years of the trial in the soil because of the deep soil tillage (25 cm) and low crop productivity irrespective of tillage type. In contrast, N content increased in all of the plots and was enhanced by fertilization. The use of chisel plough stratified the distribution of SOC and N in the surface layers (0–10 cm). Both Cmic and Cmic/SOC ratio increased in fertilized treatments, suggesting an increased lability of SOC. The application of more stabilized organic matter may be a better practice to build up soil organic matter and to maintain crop yields in organic farming systems.

Effects of organic manure and crop rotation system on potato (<i>Solanum tuberosum</i> L.) tuber yield in the highlands of Awi Zone

Lack of sustainable soil fertility management system is a critical challenge in the highlands of Awi Zone. Important physicochemical properties of the soil are below the critical level to support crop growth. Hence, a study was undertaken with the aim of improving the yield of potato through organic treatments and sound crop rotation system. Two rotation systems and four levels of organic treatments were factorially arranged and laid out in RCBD with four replications. The organic treatments were: V1 = 0 t/ha farmyards manure (FYM); V2 = 2.5 t/h fresh sesbania green manure (FSB) V3 = 5 t/ha FYM; and V4 = 5 t/ha FYM +2.5 t/ha FSB applied in fixed plots for three years. Indeed, the rotation systems varied from year to year to estimate the changes in potato tuber yields due to the differences in crop rotation systems. Tuber yields of potato showed increasing trend over the period of the three years with the lowest in the first year, intermediate in the second year and the highest in the third year across all treatments. Among all, the highest total potato tuber yield (35.15 t/ha) was obtained at the combined application of 5 t/ha FYM +2.5 t/ha FSB and clover-wheat-potato rotation system in the third year. The treatment combination increased total potato tuber yield by 140% and 41% over that of the first and the second years and would be recommended as ecologically sound option in improving the productivity of potato.Keywords: Cropping system; farmyard manure; green manure; productivity; soil management

Effects of 16‐Year Woodchip Mulching on Weeds and Yield in Organic Farming

Core Ideas Woodchip mulching significantly suppressed weeds under field conditions.Sixteen‐year woodchip mulching had no impact on grain yield of cereals or faba bean.There was a continuous decreasing trend of the relative yield with woodchip mulching.There was no impact of woodchip mulching on the weed seed bank after 16 yr. To test the possibility of using hedgerow woody waste for weed control in arable organic farming, a 16‐yr field trial with a typical organic crop rotation using three rates of woodchip mulching (WCM) was conducted in Southwest Germany. Winter cereals, fodder crops, and legumes representative for this region were included in the crop rotation. The woodchips were produced from cuttings of the hedgerows on the farm and were applied to the field in rates of 0, 80, and 160 m3 ha–1, respectively (control, WCM80, and WCM160). Weed infestations, including weed density in spring, weed biomass at crop harvest and weed seed bank, were measured in selected years. Crop yields were recorded yearly. Soil temperature and soil mineral N content were measured in selected years. In general, mean weed density was reduced in WCM160 (135 plants m–2) compared to WCM80 and the control (150 and 160 plants m–2, respectively). The relative weed density averaged across the two WCM levels was 91% of the control on average and showed no trend over time. The grain yield of cereals and faba bean (Vicia faba L.) did not significantly differ between the mulching treatments. The relative crop yield of plots with WCM compared to the control showed a decreasing trend over time. Soil temperature and diurnal temperature variation were lower in WCM160 compared to the control. Generally, combined with an adapted fertilizer application, WCM in a specific amount could be an efficient tool to control weeds in organic farming without yield loss.

Identification and characterization of pathogens associated with root rot of winter peas grown under organic management in Germany

Root rots are limiting factor for pea production worldwide. This disease is caused by a pathogen complex and the role of single pathogens is unclear. This study aimed at identifying pathogens involved in a root rot of organically grown field pea in Germany, and establishing their importance in the disease complex. The potential of yard waste compost to suppress the diseased was also studied. Average disease severity index was similar in 2010 and 2011 (DI of 4.56 to 4.59, respectively) but it increased in 2012 to DI 5.8. Peyronellaea pinodella was most frequently isolated pathogen, with isolation frequency from 86%, 73% and 86% in 2010, 2011 and 2012, respectively. In addition, Didymella pinodes, Fusarium solani f. sp. pisi, F. oxysporum f. sp. pisi and F. avenaceum were the main fungi recovered from pea roots. In pathogenicity test all of the tested pathogens caused weak symptoms on the pigmented winter variety EFB33 and moderate to severe symptoms on the white flowering summer variety Santana. F. avenaceum was the most aggressive pathogen on Santana with DI of 7.4 followed by P. pinodella with DI of 5.7. The high aggressiveness combined with the wide host range highlights the possibility of F. avenaceum emerging as potential risk for organic crop rotation. High levels of resistance of EFB33 against all pathogens shows the potential of this variety to serve as a resource in further research for identification and development of new sources of resistance against root rot diseases of pea.

Nitrous oxide emissions with organic crop production depends on fall soil moisture

Agriculture is the major anthropogenic contributor to global nitrous oxide (N2O) emissions. Many studies have examined soil N2O emissions from synthetic nitrogen (N) fertilizer additions, however, in organic production where plough-down of forage legumes are often used as a nitrogen source, emissions are as not well understood. In the current study, the Glenlea Long-Term Organic Crop Rotation Study near Winnipeg, Manitoba, was used to compare N2O emissions of a conventional annual grain and an organic mixed forage-grain system. Static-vented chambers were used to determine N2O emissions for the 2014 and 2015 crop years; from spring planting to freeze-up and again during thaw following spring. plots monitored were spring wheat and two-cut harvest with late-summer or early-fall plough-down alfalfa for the organic system, and spring wheat and soybean for the conventional system were monitored in each study year. The organically produced alfalfa received composted dairy manure in 2014 and only conventional wheat crops received fertilizer N as urea. Cumulative emissions (gN2O-Nha−1) with organic wheat were half that of conventional management. Cumulative emissions for the legume crops in the 2014 crop year were very low (<200gNha−1) and not affected by management. No or very low emissions occurred shortly after plough-downs in 2014 and 2015, and during thaw in 2015. However, fall soil moisture was higher in 2015 resulting in nitrate accumulation from alfalfa plough-down and high subsequent N2O emissions during spring thaw in 2016. Over both study years, management did not affect yield-scaled emissions for wheat unless thaw emissions from ploughed down alfalfa were included. In conclusion, the benefit of organic cropping on N2O emissions was dependent upon the soil moisture level in fall that preceded the spring thaw period.

Comparing crop rotations between organic and conventional farming

Cropland use activities are major drivers of global environmental changes and of farming system resilience. Rotating crops is a critical land-use driver, and a farmers’ key strategy to control environmental stresses and crop performances. Evidence has accumulated that crop rotations have been dramatically simplified over the last 50 years. In contrast, organic farming stands as an alternative production way that promotes crop diversification. However, our understanding of crop rotations is surprisingly limited. In order to understand if organic farming would result in more diversified and multifunctional landscapes, we provide here a novel, systematic comparison of organic-to-conventional crop rotations at the global scale based on a meta-analysis of the scientific literature, paired with an independent analysis of organic-to-conventional land-use. We show that organic farming leads to differences in land-use compared to conventional: overall, crop rotations are 15% longer and result in higher diversity and evener crop species distribution. These changes are driven by a higher abundance of temporary fodders, catch and cover-crops, mostly to the detriment of cereals. We also highlighted differences in organic rotations between Europe and North-America, two leading regions for organic production. This increased complexity of organic crop rotations is likely to enhance ecosystem service provisioning to agroecosystems.

Pengurangan Dosis Pupuk pada Produksi Sawi Hijau Organik dengan Pergiliran Tanaman Jagung dan Kedelai

&lt;p&gt; The application of organic fertilizer and crop rotation are combination of cultivation system integrally to preserve land fertility. This study aimed to determine the effect of crop residues produced in the first season to reduce organic fertilizer rate for mustard greens cultivation in the second season. The experiment was conducted at IPB organic farm, Cikarawang, Darmaga in April until June 2015. The first season was the first experiment conducted separately for soybean and corn to study different manure types for both crops which the rate of each manure was 20 ton ha-1 for soybean and 25 ton ha-1 for corn. Soybean and corn residues were used in the following season on mustard green cultivation. The experimental design was split plot design with crop residues as main plot, and combination of manure types (chicken, cow, goat) and rates (0, 10 ton ha-1) as sub plot. Data were analyzed using variance. Means were statistically compared with Tukey test at α &amp;lt; 0.05 level. The results showed that the soybean and corn residues can be used as nutrient sources for mustard greens cultivation. The application of manure was not necessary for mustard greens cultivation if soybean or corn residues were added in the second season and there was residues from manure in the first season.&lt;br /&gt;&lt;br /&gt;Keywords: chicken manure, cow manure, crop residue, goat manure &lt;br /&gt;&lt;br /&gt;&lt;br /&gt;&lt;/p&gt;

Biological nitrogen fixation in three long-term organic and conventional arable crop rotation experiments in Denmark

Abstract Biological nitrogen (N) fixation (BNF) by legumes in organic cropping systems has been perceived as a strategy to substitute N import from conventional sources. However, the N contribution by legumes varies considerably depending on legumes species, as well as local soil and climatic conditions. There is a lack of knowledge on whether the N contribution of legumes estimated using short-term experiments reflects the long-term effects in organic systems varying in fertility building measures. There is also limited information on how fertilizer management practices in organic crop rotations affect BNF of legumes. Therefore, this study aimed to estimate BNF in long-term experiments with a range of organic and conventional arable crop rotations at three sites in Denmark varying in climate and soils (coarse sand, loamy sand and sandy loam) and to identify possible causes of differences in the amount of BNF. The experiment included 4-year crop rotations with three treatment factors in a factorial design: (i) rotations, i.e. organic with a year of grass-clover (OGC), organic with a year of grain legumes (OGL), and conventional with a year of grain legumes (CGL), (ii) with (+CC) and without (−CC) cover crops, and (iii) with (+M) and without (−M) animal manure in OGC and OGL, and with (+F) mineral fertilizer in CGL. Cover crops consisted of a mixture of perennial ryegrass and clover (at the sites with coarse sand and sandy loam soils) or winter rye, fodder radish and vetch (at the site with loamy sand soil) in OGC and OGL, and only perennial ryegrass in CGL at all sites. The BNF was measured using the N difference method. The proportion of N derived from the atmosphere (%Ndfa) in aboveground biomass of clover grown for an entire year in a mixture with perennial ryegrass and harvested three times during the growing season in OGC was close to 100% at all three sites. The Ndfa of grain legumes in both OGL and CGL rotations ranged between 61% and 95% depending on location with mostly no significant difference in Ndfa between treatments. Cover crops had more than 92% Ndfa at all sites. The total BNF per rotation cycle was higher in OGC than in OGL and CGL, mostly irrespective of manure/fertilizer or cover crop treatments. There was no significant difference in total BNF between OGL and CGL rotations, but large differences were observed between sites. The lowest cumulated BNF by all the legume species over the 4-year rotation cycle was obtained at the location with sandy loam soil, i.e. 224–244, 96–128, and 144–156 kg N ha−1 in OGC, OGL and CGL, respectively, whereas it was higher at the locations with coarse sand and loamy sand soil, i.e. 320–376, 168–264, and 200–220 kg N ha−1 in OGC, OGL and CGL, respectively. The study shows that legumes in organic crop rotations can maintain N2 fixation without being significantly affected by long-term fertilizer regimes or fertility building measures.

Productivity of organic and conventional arable cropping systems in long-term experiments in Denmark

Abstract A field experiment comparing different arable crop rotations was conducted in Denmark during 1997–2008 on three sites varying in climatic conditions and soil types, i.e. coarse sand (Jyndevand), loamy sand (Foulum), and sandy loam (Flakkebjerg). The crop rotations followed organic farm management, and from 2005 also conventional management was included for comparison. Three experimental factors were included in the experiment in a factorial design: 1) crop rotation (organic crop rotations varying in use of whole-year green manure (O1 and O2 with a whole-year green manure, and O4 without), and a conventional system without green manure (C4)), 2) catch crop (with and without), and 3) manure (with and without). The experiment consisted of three consecutive cycles using four-course rotations with all crops present every year, i.e. 1997–2000 (1st cycle), 2001–2004 (2nd cycle), and 2005–2008 (3rd cycle). In the 3rd cycle at all locations C4 was compared with two organic rotations, i.e. O2 and O4. The O2 rotation in the third cycle included spring barley, grass-clover, potato, and winter wheat, whereas C4 and O4 included spring barley, faba bean, potato, and winter wheat. For the O2 rotation with green manure there was a tendency for increased DM yield over time at all sites, whereas little response was seen in N yield. In the O4 rotation DM and N yields tended to increase at Foulum over time, but there was little change at Flakkebjerg. The DM yield gap between organic and conventional systems in the 3rd cycle varied between sites with 34–66% at Jyndevad, 21–44% at Foulum, and 32–52% at Flakkebjerg. The inclusion of grass-clover resulted in lower cumulated yield over the rotation than the treatment without grass-clover. The use of manure reduced the DM yield gap between conventional and organic systems on an average by 15 and 21%-points in systems with and without grass-clover, respectively, and the use of catch crops reduced the yield gap by 3 and 5%-points in the respective systems. Across all crops the agronomic efficiency of N in manure (yield benefit for each kg of mineral N applied) was greater in O4 compared with O2 for all crops.

Organic production of horticultural crops with green manure, composted farmyard manure and organic fertiliser

A three-year organic crop rotation was set up in a field with sandy loam soil, with a cover crop of rye and vetch grown over the three autumn/winter seasons for green manure, followed by potato and lettuce (1st year), Swiss chard and turnip (2nd year), and Portuguese cabbage and carrot (3rd year). Nitrogen (N) mineralisation was determined by field incubation in response to green manure (GM), GM with 20 and 40 t ha−1 farmyard manure (FYM) compost (C20 and C40) and GM with 1 and 2 t ha−1 of commercial organic fertiliser (CF1 and CF2). The second season crops (lettuce, turnip and carrot) yields were higher for the treatment C40 compared to all other treatments because most of the commercial fertiliser was mineralised during the previous crop. Swiss chard, grown in a short season (54 days), produced higher yield for CF2 compared with C40. However, this was not true for potato (1st year), probably because of increased compost mineralised N recovery during the longer growing season for the potatoes (124 days), nor for the cabbage (3rd year), which had a short growing season (56 days), because of increased N availability with continuous compost and green manure application. This study highlighted that field incubation can be used to assess mineralisation rates and that the fast N release of commercial fertilisers increased the yield of the first crop of the year, whereas the slowly released N of FYM compost increased yield of both crops of the year, with lower risk of N loss.

Rotating alfalfa with dry bean as an alternative to corn-soybean rotations in organic systems in the Upper Midwest

AbstractDry bean (Phaseolus vulgaris) can be grown as a local food source and as an alternative to soybean (Glycine max) to diversify organic crop rotations. To understand the benefits of diversification of organic cropping systems, the effects of preceding alfalfa (Medicago sativa) and corn (Zea mays) crops on yields of five dry bean types and one soybean type, and the effect of bean type on following spring wheat (Triticum aestivum) yields, were tested at four Minnesota locations. Dry bean and soybean yields following alfalfa were 25% greater than yields following corn at two of four locations, though bean yields following corn were greater at one location. A preceding alfalfa crop benefited bean yields at locations where hog manure or no manure was applied to corn, whereas bean yields following corn fertilized with cow manure were similar to or greater than bean yields following alfalfa. Among dry bean types, black bean yielded similarly to soybean at three of four locations, but dark red kidney bean consistently yielded 25–65% lower than soybean. Navy, pinto and heirloom dry bean types yielded similarly to soybean at two of four locations. Across locations, weed biomass was 3–15 times greater in dry bean than in soybean and dry bean yield response to weed competition varied among bean types. However, dry bean, regardless of the preceding crop, demonstrated the potential to produce yields comparable with soybean in organic systems and the substitution of dry bean for soybean did not affect subsequent wheat yields. More studies are needed to identify nitrogen fertility dynamics in organic systems as they relate to dry bean yield.

Long-term negative phosphorus budgets in organic crop rotations deplete plant-available phosphorus from soil

AbstractIn organic farming, phosphorus (P) can be imported in mineral form with rock phosphate, feedstuff for livestock or suitable organic fertilizers. Many organic farmers, however, rely on biological activation of soil P reserves and tolerate P deficits, not knowing when soil reserves will be depleted. We hypothesized that under conditions of a long-term negative P budget in organic farming, the decline in readily available soil P pools would be less pronounced in dairy systems (arable land and grassland) than in stockless systems (arable land), due to higher shares of forage legumes in crop rotations, longer plant soil coverage, and manure backflow. From 2001 to 2013, we analyzed those systems on one site in North Germany. We assessed topsoil for plant-available soil P concentration [P(CAL)], mineral soil P fractions (Hedley), organic P, acid and alkaline phosphatase, and microbial activity (dehydrogenase). We measured P(CAL) each year on all fields of the crop rotations and grassland. The other soil characteristics were determined only in selected fields in 2001, 2009, and 2013. We observed that in grassland, all mineral P fractions, organic P contents, and microbial activity were considerably higher than in arable fields. On average, soil P(CAL) content decreased significantly in all systems (stockless arable −1.71, dairy arable −1.41, grassland −3.18 mg P kg−1 year−1), but the soil threshold value deemed to be sufficient for P supply (>44 mg kg−1) was preserved. The readily available inorganic P fractions (H2O-P, NaHCO3-P) were also lower in 2013 than in 2001. Our data does not support a different development in either arable system. We could show that higher shares of forage legumes and manure recycling in an organic mixed arable dairy crop rotation and grassland do not necessarily mitigate decreases of plant-available P contents in soil as compared to a stockless system.

Soybeans in high latitudes: effects of Bradyrhizobium inoculation in Northwest Germany and southern West Siberia

In regions around the current high-latitude boundaries of agricultural production, the effects of climate change are likely to affect future growing conditions. Specifically for soybeans (Glycine max (L.) Merr.), this leads to a northward shift of the northernmost limit for cultivation. In two high-latitude regions with cold growing conditions (northwest Germany and southern West Siberia, Russia), similar field trials were conducted under different climate conditions (temperate oceanic, temperate continental). The effect of soybean seed inoculation with Bradyrhizobium japonicum was investigated in comparison to untreated control in five field site-years under organic farming conditions. SPAD meter readings were used to indicate differences in leaf chlorophyll content between inoculation and control at three phenological development stages. To make SPAD values from different varieties and development stages comparable, effect sizes (‘Hedges’ d’ of inoculation against control) were calculated. Inoculation was always successful, and significant numbers of active nodules developed only with inoculation. Effect sizes of SPAD values were significantly positive in inoculated plots at the beginning of seed filling but did not differ earlier. Except for the warmest site-year, inoculation did not affect seed yield. Protein content was significantly higher with inoculation at most varieties tested in Germany but only once in Russia. Protein yield was only in the warmest site-year significantly higher with inoculation. Under cold growing conditions of high-latitude regions, temperature sums seemed to limit soybean yield and the effectiveness of inoculation with B. japonicum. To implement soybeans as legumes in organic farming crop rotations, nevertheless, inoculation is mandatory, since soils at high latitudes lack soy-specific rhizobia bacteria.

Soil Health Benefit to Composted Manure Application and Insertion of a Sod Component in a Long-term Organic Crop Rotation

In organic production systems, composted manure and a short-term grass/legume sod rotation component may improve soil health. However, little is known about the lasting benefits of these two management practices for the duration of the several crop components of an organic rotation. This study was designed to determine whether 3 years of grass sod and composted manure application affected soil properties and crop biomass yield at the beginning and end of 4 years of organic crop production. The effects of the sod rotation component and composted manure on bulk density (BD), dry (dryGMD [dry aggregate geometric mean diameter]) and wet (wetGMD [wet aggregate geometric mean diameter]) aggregation, soil organic matter, bioavailable nutrient concentrations, and crop biomass were determined in two long-term rotations at the West Virginia University Certified Organic Research Farm in Morgantown, West Virginia. The rotations were a 4-year continuous rotation of corn (Zea mays L.), soybean (Glycine max L. Merr.), wheat (Triticum aestivum L.), and kale/cowpea (Brassica oleracea)/Vigna unguiculata L. Walp.), and a 7-year rotation of the same crop sequence followed by 3 years of grass/legume (orchardgrass/red clover, Dactylis glomerata L./Trifolium pretense L.) sod. Two composted manure levels, 0 (nonmanured [n-M]) and 2.25 (manured [M]) Mg ha−1, were imposed only to the corn and wheat rotation components. Results for 2013 and 2014 showed that manure application significantly improved soil physical and chemical properties for corn and kale/cowpea regardless of the sod component. In the corn component, BD was lower (P < 0.0001) in M soils (1.13 Mg m−3) than in n-M soils (1.24 Mg m−3). A significant (P = 0.0060) decrease in BD due to the sod component was observed when corn was not manured, 1.27 and 1.21 Mg m−3 in the 4- and 7-year rotations, respectively. Soil organic matter was significantly (P < 0.0001) higher in M than n-M soils and was also higher for the rotation with the sod component, regardless of manure application (P < 0.0001). The sod component resulted in significantly (P = 0.012) increased pH in n-M soils (5.61 and 5.89 for the 4- and 7-year rotations, respectively). Soil health and corn biomass were found to be most improved in soils receiving manure and subject to sod insertion in the rotation. The soil organic matter, dryGMD, wetGMD, and bioavailable soil P and Mg were found to be higher in M soils under corn in the 7-year rotation. Although differences in soil health indicators were measured in kale/cowpea soils, no differences (P = 0.510) in the biomass indicator were observed. This research supports the use of manure, in conjunction with insertion of a short-term grass/legume sod component, to improve soil health in organic crop rotations.

Impacts of Land Use Types on Selected Soil Physico-Chemical Properties of Loma Woreda, Dawuro Zone, Southern Ethiopia

A study was conducted in Loma Woreda, Dawuro Zone, Southern Ethiopia, to investigate the impacts of land use types (forest, grazing and cultivated) on the selected soil physico chemical properties of the study area. Composite surface (0-20 cm) soil samples were collected randomly from three sites of each land use which were adjacent to each other and subjected to laboratory analysis. The results of the study revealed that there was relative variation in proportion of sand and clay content among the land use types though they have the same textural class. The bulk density of the soils decreased from grazing to cultivated and then to forest land, while total porosity decreased from forest to cultivated and then to grazing lands. The average soil pH-H2O value of the area varied from very strongly acidic to strongly acidic. Exchangeable acidity and Percent Acid Saturation were significantly lower by about 60.02 and 61.54% in the forest soils than the soils of cultivated lands, and 29.70 and 38.32% than that of grazing lands, respectively. As compared to the soils of forest land, the amount of soil OM, TN and CEC in cultivated land have declined by about 76.53, 60.83 and 38.97%, respectively. The available P, exchangeable bases and PBS have shown decreasing trends in the soils of forest to grazing and then to cultivated land uses. From this study, it can be concluded that the soil fertility and quality were well maintained relatively under the forest land, while the impact on most parameters were negative on the soils of the cultivated land. Applications of lime, organic and inorganic fertilizers and crop rotation especially in the cultivated lands may enhance the productivity of the soils, implying the need for undertaking integrated soil fertility management in sustainable way to improve and maintain the favorable soil properties.

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.