Search

The species structure of plant parasitic nematode populations from the rhizosphere of winter wheat grown with crop rotation or in 48-year-old monoculture was analyzed and compared. Dominating species: Bitylenchus dubius, Merlinius microdorus, Paratylenchus neglectus and Heterodera avenae, in monoculture plots, had higher populations than in crop rotation plots. Heterodera avenae eggs and larvae were infected by pathogenic fungi in 68% of the monoculture crops (vs. 65-66% of the cysts from crop rotation), 12-20% of Paratylenchus sp. specimens were colonized by bacteria, mainly by Bacillus penetrans. This study shows nematological changes occurring in long-term wheat breeding, thus providing additional information necessary to fight dangerous viral vectors of the examined cereal. [ABSTRACT FROM AUTHOR]

[Objective]To provide theoretical basis for soil shrinkage cracks and theoretical guidance for the safe growth of rice, the soil shrinkage changes in paddy fields under different tillage conditions were studied. [Method] The paddy fields were studied under the conditions of rotation and non-rotation. Under the different soil moisture contents, tin; soil shrinkage curve model modified by van-Genuchten e-quation was used to study tin; variation of soil linear extension coefficient and the fitting of soil shrinkage curve in paddy fields. [Result]The SSS software could fit tin; measured data well (R2 >0.91) ; under the rotation condition, tin; soil clay content was greater than non-rotation, but soil porosity was opposite; The linear extension coefficient of soil decreased with the increase of soil depth, the soil shrinkage curves in tin; 0-8 cm soil layer and 18-26 cm soil layer showed‘ S’ type in tin; rotation area, however, it showed a linear relationship in the 40-46 cm soil layer under tin; non-rotation condition; Under the different soil moisture content, tin; soil shrinkage ability was different, and tin; greater tin; soil moisture content was, tin; more obvious tin; soil shrinkage was, and tin; positive correlation between them. [Conclusion]Compared with tin; non-rotation, tin; rotation could effectively improve soil physical and chemical properties, regulate soil structure, and enhance soil shrinkage. [ABSTRACT FROM AUTHOR]

Chiselling has been used to alleviate soil compaction but cover crops with deep, vigorous roots can improve root growth and activity of the cash crop for a longer time. The determination of root activity in addition to root mass or length may improve the understanding of plant response to compaction. The objective of this experiment was to evaluate root growth and activity as affected by the alleviation of soil compaction using mechanical and biological methods. The experiment was conducted in Botucatu, São Paulo, Brazil, from 2009 to 2011, on a clay, Typic Rhodudalf soil. Crop rotations including pear millet ( Pennisetum glaucum), soybean ( Glycine max), grain sorghum ( Sorghum bicolor), maize ( Zea mays), ruzi grass ( Brachiaria ruziziensis) and castor bean ( Ricinus communis) in plots, either chiselled or not. Root growth was assessed by core sampling and root activity was determined indirectly using rubidium injected at several depths as a marker. Root activity was instrumental in interpreting the effects of tillage and crop rotations on soil amelioration. Compared with the initial compacted condition, chiselling increased root growth and activity just for the first 18 months of the experiment, but crop rotations, mainly including ruzi grass and castor bean, increased root growth and activity in the soil profile from the second year on. Generally, root mass was poorly correlated with root activity, except in the case of ruzi grass. Introduction of ruzi grass plus castor bean into the cropping system improves not only root growth and activity in the soil profile but also soybean yield. [ABSTRACT FROM AUTHOR]

The frequency, size and development rate of Vertisols cracks influence the water, solute and heat dynamics and hence on the crop productivity. The aim of this study was to evaluate the effect of the tillage system and crop rotation on the behaviour of cracks and soil compaction in a long-term experiment that was initiated in 1986 on a Mediterranean rainfed Vertisol in southern Spain. The treatments studied were conventional tillage (CT) vs. no-tillage (NT) for five crop rotations: wheat ( Triticum aestivum L.) - chickpea ( Cicer arietinum L.), wheat - sunflower ( Helianthus annuus L.), wheat - faba bean ( Vicia faba L.), wheat - bare fallow and continuous wheat. The following parameters were measured: penetration resistance, water content at harvest, and perimeter, depth and width of crack. Soil compaction was greater in NT compared to CT in the top 10 cm of soil, with the opposite occurring between 10 and 40 cm. The surface area and volume of cracks was significantly greater in CT than in NT. The perimeter of the cracks was greater in wheat monoculture plots but with smaller crack width and depth in relation to the other studied biannual rotations. The water content at harvest recorded in the first 30 cm of soil was negatively correlated with the depth of cracks. The characterization of the cracks in Vertisols is very important for estimating losses or recharging the water in the soil profile as well as for evaluating its compaction and stability. [ABSTRACT FROM AUTHOR]

Bangladesh needs to produce more food on less land to assure future food security for an increasing population. The two techniques that need to be adopted more frequently are an increase in cropping intensity by producing two or more crops on the same piece of land, and an increase in the productivity of individual crops, particularly their ability to utilize basic or limiting resources such as water and nutrients. In this context, the present study was carried out to assess the most suitable crop rotation based on the dose of organic and inorganic fertilizers as a source of plant nutrients. The potato–mungbean–T. (transplanted) Aman rice (P-M-R) crop rotation was applied to three agro-ecological zones (AEZs) of Bangladesh (Bogra, AEZ-25; Joydebpur, AEZ-28; Jessore, AEZ-11). The results from a two-year experiment indicate that the yield of P-M-R was influenced by the nutrient management applied. Except for potato, higher yield was obtained in the second year. The yield of potato and T. Aman rice was highest when crop residues were incorporated. In all locations, N (nitrogen) and K (potassium) were depleted in both years, but P (phosphorus), S (sulphur), Zn (zinc) and B (boron) showed a positive balance. Even after completing two cropping cycles and incorporating crop residues with different levels of nutrients, there was little change in soil pH, organic matter (%), total N (%), P, K, S, Zn and B. However, in all three locations, organic matter (%), total N (%), P, K, S, Zn and B increased in plots into which crop residues had been incorporated. The soil test-based nutrient management choice that incorporated crop residues gave a higher net return (3506 US$ ha −1 ) than other nutrient management combinations (3351–3483 US$ ha −1 ). These results indicate that soil test-based nutrient management and an integrated plant nutrient system that incorporates crop residues are suitable for the potato–mungbean–T. Aman rice crop rotation in multiple environments of Bangladesh. [ABSTRACT FROM AUTHOR]

Agricultural crop rotations have been shown to increase soil carbon (C), nitrogen (N), and microbial biomass. The mechanisms behind these increases remain unclear, but may be linked to the diversity of crop residue inputs to soil organic matter (SOM). We used a residue mixture incubation to examine how variation in long-term diversity of plant communities in agroecosystems influences decomposition of residue mixtures, thus providing a comparison of the effects of plant diversification on decomposition in the long term (via crop rotation) and short term (via residue mixtures). Three crop residue mixtures, ranging in diversity from two to four species, were incubated for 360 d with soils from five crop rotations, ranging from monoculture corn (mC) to a complex five-crop rotation. In response, we measured fundamental soil pools and processes underlying C and N cycling. These included soil respiration, inorganic N, microbial biomass, and extracellular enzymes. We hypothesized that soils with more diverse cropping histories would show greater synergistic mixture effects than mC. For most variables (except extracellular enzymes), crop rotation history, or the long-term history of plant diversity in the field, had a stronger effect on soil processes than mixture composition. In contrast to our hypothesis, the mC soil had nearly three and seven times greater synergistic mixture effects for respiration and microbial biomass N, respectively, compared with soils from crop rotations. This was due to the low response of the mC soils to poor quality residues (corn and wheat), likely resulting from a lack of available C and nutrients to cometabolize these residues. These results indicate that diversifying crop rotations in agricultural systems alter the decomposition dynamics of new residue inputs, which may be linked to the benefits of increasing crop rotation diversity on soil nutrient cycling, SOM dynamics, and yields. [ABSTRACT FROM AUTHOR]

The effect of land use change from agricultural to short rotation woody crops on soil respiration and its temperature sensitivity is not fully understood. We studied the effect of land use change on soil respiration, in a factorial experiment, 4 years after converting an agricultural field to a Walker poplar ( Populus deltoides × Populus × petrowskyana var. Walker) plantation in the boreal region of northeastern Alberta. Overall, total soil respiration was greater in the agricultural plots (planted to alfalfa, Medicago sativa L.) than in the poplar plots. Soil respiration and soil temperature at the 10-cm depth in both land uses had similar seasonal and diurnal variations. The season-long temperature sensitivity (Q) of daily and nighttime soil respiration in the alfalfa plots was greater than that in the poplar plots, with Q values of 5.4 vs. 4.9, respectively. Our data also show that, 4 years after land use conversion, the heterotrophic respiration was smaller in the poplar plots than in the adjacent agricultural plots, indicating potential benefits of plantation establishment in reducing heterotrophic respiration. However, the temperature sensitivity of soil respiration based on monthly nighttime rates, which minimizes the plant phenological influences, was greater in the poplar plantation, suggesting that soil respiration could become greater in the poplar plantation under a future warmer climate. We conclude that establishment of poplar plantations, which are known to have a fast rate of biomass production for long-term carbon storage, may help mitigate climate change by reducing heterotrophic and total soil respiration in the Canadian boreal region, but the long-term implications (e.g., changes in the temperature sensitivity of soil respiration over time) need to be further studied. [ABSTRACT FROM AUTHOR]

The concentration and temporal trend of PBDEs in farmland soil during a circle of crop rotation period within an e-waste dismantling area of South China were investigated. The averaged current concentration of total PBDEs in the farmland soil was averaged 19.1 ± 20.7 ng/g dry weight, which was much lower than the PBDE level in roadside soil and in topsoil near e-waste dismantling sites. Spatial distribution of total PBDEs concentration in the study area showed higher level at the field near e-waste workshops and lower at the distanced farmland area. Soil organic carbon content was significantly correlated with concentration of BDE209 ( r = 0.704, p < 0.01), but not related with the sum concentration of other PBDE compounds ( r = 0.097, p > 0.1). During the whole crop rotation circle, the temporal concentration of PBDEs in the farmland soil was highest (25.3 ± 11.4 ng/g dry wt.) in April when early paddy had been transplanted for 1 or 2 weeks. When the crop rotated to autumn peanut in August and the land is turning dry, the PBDEs concentration in farmland soil reached the lowest level which was 8.1 ± 1.2 ng/g dry wt. The temporal trend of PBDEs in farmland soil was not consistent with that of atmospheric PBDEs and soil total organic carbon (TOC) content during the rotation cycle. It was concluded that the dynamics of PBDEs in the farmland soil is influenced by multiple, interacting factors, and not clearly related to neither the atmospheric deposition nor the organic carbon content of the soil, but possibly related to the micro-environmental conditions changed by crop rotation process. [ABSTRACT FROM AUTHOR]

Verticillium wilt, caused by Verticillium dahliae, reduces yields of potato and mint. Crop rotation is a potential management tactic for Verticillium wilt; however, the wide host range of V. dahliae may limit the effectiveness of this tactic. The hypothesis that rotation crops are infected by V. dahliae inoculum originating from potato and mint was tested by inoculation of mustards, grasses, and Austrian winter pea with eight isolates of V. dahliae. Inoculum density was estimated from plants and soil. Typical wilt symptoms were not observed in any rotation crop but plant biomass of some crops was reduced, not affected, or increased by infection of specific isolates. Each isolate was host-specific and infected a subset of the rotation crops tested but microsclerotia from at least one isolate were observed on each rotation crop. Some isolates were host-adapted and differentially altered plant biomass or produced differential amounts of inoculum on rotation crops like arugula and Austrian winter pea, which supported more inoculum of specific isolates than potato. Evidence of asymptomatic and symptomatic infection and differential inoculum formation of V. dahliae on rotation crops presented here will be useful in designing rotations for management of Verticillium wilt. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fallow lands in ancient agricultural areas of Northwestern Crimea which had experienced repeated phases of agricultural activity at different time periods (the Late Bronze Age, antiquity, and the last 150−200 years) have been studied. Differences in biogeochemical fluxes for virgin and fallow soils are analyzed from the chemical elements determining the composition of secondary clay minerals. The most informative and evolutionarily significant biogeochemical indicators of relict agricultural loads and duration of fallow periods are specified. [ABSTRACT FROM AUTHOR]

Although riparian zones provide numerous ecological services, they have been widely degraded by agricultural intensification. To recover water quality and restore other critical services, tree planting has been implemented in agricultural riparian buffer zones worldwide. However, intensive agricultural practices adjacent to tree plantations are likely to impede their establishment. In this study, we assessed the survival and size of trees planted in riparian buffer zones along a gradient of agriculture intensification. We studied 68 riparian buffer zones in two agricultural watersheds of southeastern Québec (Canada) where trees had been planted 3–17 years prior to sampling. Tree survival and size (height, diameter and crown width) were measured and related to agricultural intensification, quantified as the frequency of annual crops in the agricultural field adjacent to riparian zones during the seven years prior to sampling. Tree survival decreased by 25% with increasing frequency of annual crops ( P < 0.0001; R 2 = 35%), independently of the planting year. Aside from the influence of tree age, tree size varied with the frequency of annual crops but only for three of the six most frequently planted tree species ( P = 0.0007; R 2 = 46%). These three species ( Fraxinus pennsylvanica Marsh., Quercus macrocarpa Michx. and Picea glauca (Moench) Voss) showed reduced size with higher cultivation frequency of annual crops, whereas the other three species ( Acer saccharum Marsh., Larix laricina (Du Roi) K. Koch and Quercus rubra L.) were more tolerant to agricultural intensification. While tree planting is carried out in riparian buffer zones to mitigate the environmental impacts of agricultural practices, agricultural intensification in turns impedes the establishment success of trees. To increase the environmental benefits provided by agroforestry projects, tree planting in riparian buffer zones should focus on species that tolerate agricultural intensive practices. Additionally, more frequent inclusion of hay meadows in the crop rotation of fields adjacent to riparian buffer zones may be beneficial to the establishment success of planted trees. [ABSTRACT FROM AUTHOR]

Background and Aims: Managing soil organic matter (SOM) levels in agricultural systems has focused predominantly on the quantity of plant residues returned to the soil but residue quality may also affect SOM stores and dynamics. Our objective in this research was to evaluate the influence of crop rotation on SOM storage and dynamics in a long-term field experiment using particle size fractionation and natural abundance C. Methods: Soils were collected from an 18-year maize ( Zea mays L.) and soybean ( Glycine max (L) Merr.) cropping experiment that imposed a natural shift in the C isotope ratio of SOM with no addition of fertilizer nitrogen (N). We fractionated soils from time zero and year 18 into three size fractions (>53 μm, 5-53 μm, <5 μm), analyzed the whole soils and fractions for their elemental concentrations and C isotope ratios, and calculated the storage and turnover of C and N in the soil. Results: Soil C and N levels declined in all cropping treatments over time. The quantity and quality of residues returned to the soil over the experimental period differed among the rotation treatments but there was no rotation effect on the storage of C and N in the whole soil or any fraction. The rate of soil C and N loss was positively related to the quantity of residues returned to the soil, suggesting that in this C- and N-limited system, residue addition stimulated decomposition of recalcitrant C. Conclusions: This study indicates that C inputs alone may not be sufficient for increasing SOC stores and that the availability of nutrients in the plant-soil system must also be considered, particularly when N inputs are limiting. Our results suggest that in a C- and N-limited system, additions of fresh residues may stimulate the microbial community to mine recalcitrant stores of SOM for N, thereby resulting in losses of otherwise stable SOM stores by priming. [ABSTRACT FROM AUTHOR]

Sole pearlmillet and their intercropping combinations during kharif followed by wheat grown with three nitrogen levels i.e 50, 75 and 100 % of recommended dose of nitrogen (RDN) to identify the profitable system. Based on two year study the net return and B:C ratio under Sesbania-wheat rotation were 17.9% and 7.1% more over pearlmillet-wheat crop rotation, respectively. Among intercropping systems Sesbania sown at 90 cm spacing intercropped with one row of pearlmillet followed by wheat was the most profitable crop rotation for the farmers who are interested in seed crop of sesbania with net return (Rs 40013/ha) and B:C ratio (1.48) along with highest Sesbania seed yield of (924kg/ha) with an additional pearlmillet yield (743kg/ha) and wheat equivalent yield (6656kg/ha). Sesbania sown at 120 cm spacing intercropped with two rows of pearlmillet followed by wheat was the most profitable crop rotation for farmers, who are more interested in pearlmillet seed crop with the highest net return ( Rs 40593/ha) and B:C ratio (1.48) along with highest pearlmillet seed yield (1344 kg/ha), Sesbania seed yield (762 kg/ha), highest sesbania equivalent yield (1379 kg/ha) and second highest wheat equivalent yield (6661kg/ha) among intercropping systems. So, Sesbania followed by wheat is more profitable over pearlmillet- wheat crop rotation and from sustainability point of view to encourage the farmers for seed production of Sesbania and to get maximum net return, the Sesbania can be intercropped with one or two rows of pearlmillet. Sesbania sole or in combination with pearlmillet as intercrop was found beneficial for soil health improvement in terms of available N,P and K status of soil as compared to pearlmillet sole-wheat rotation. [ABSTRACT FROM AUTHOR]

During the period 2011-2013 a monitoring of entomofauna was performed in environmentally justified crop rotation including alternation of legumes (field beans, forage peas) with cereals (wheat, malting barley). Conventional entomological methods were used for identification of species and population density of harmful insects and their entomophaga. The results were processed according to the crops. In no one of the four crops, pests in density over Economic Injury Level were detected. Diversity of entomophaga was explained via the favorable ecological environmental conditions and namely by the presence of the trophic factor and the absence of chemical treatments with insecticides. [ABSTRACT FROM AUTHOR]

The article presents research concerning the genetic inheritance factors surrounding biological resistance to the agricultural pest Meloidogyne incognita, also known as Southern root-knot nematodes, within Sorghum bicolor cultivars. Comparisons are made between Honey Drip and Collier cultivars of the plant, identifying two quantitative trait loci on chromosome 3 of the plant for both plant height and pest resistance.

A combination of linear and weighted goal programming for crop rotation planning has been used in developing a tool/model for solving several management goals simultaneously. The model was implicated for the case of organic farming in Slovenia. The results yielded reasonably accurate information regarding different economic parameters and nitrogen off-take from calculated crop rotation. The model was tested in four different scenarios with the influence of various goals' weighting the results. From the obtained results, it is obvious that a combination of weighted goal programming and linear programming gives rise to a better solution from an economic perspective (i.e. higher total income per crop rotation and lower costs per crop rotation). It also provides a better solution for diversified and economically feasible crops for inclusion in crop rotation compared with the situation when farmers use only a linear mathematical technique. An investigation of the results showed that the model does not prefer mono-crop production strategies, which represent crucial drawbacks for organic agriculture, such as soil depletion, diseases and pests outbreak and soil degradation. The developed model can help farmers to obtain answers regarding four main issues in crop rotation planning; i) cropping strategy, ii) potential hiring of extra resources, iii) quantity of harvested crops and iv) quantity of fertilizer being saved in the second year of planning. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We conducted an on-farm experiment to establish corn-triticale rotational cropping system for producing organic forage, using white clover living mulch ( LM). A 2-ha experimental field has been managed according to the Japanese Agricultural Standard for organic feed production since 2003, and two cropping systems ( LM and tillage cultivation [ TC]) combined with two compost application methods (with and without compost application before planting) were tested as four corn cultivation treatments from 2008 to 2009. White clover was sown in the autumn of 2008, and corn was cultivated from June to October 2009 using the four treatments and without any application of chemical herbicides and fertilizers. After the corn harvest, the two treatments of compost application were set up again within each corn cultivation treatment, resulting in a total of eight treatments. Triticale was cultivated in those treatments from October 2009 to June 2010, without chemical herbicides or fertilizers. The results of the treatments showed that LM suppressed weed growth and increased nitrogen (N) uptake and yield of corn compared to the TC treatment. The dry matter yields of corn were the highest and the dry weight of the weeds were the lowest in the LM treatment with compost application before planting. Furthermore, the positive effect of LM on N supply was preserved during the cropping of triticale. Therefore, we concluded that the total dry matter yield of forage crops in corn-triticale rotation could be increased by using white clover LM with compost application to suppress weed growth and to increase the N uptake both of the main and succeeding crops. White clover LM is a useful cultivation technique for organic production of forage crops. [ABSTRACT FROM AUTHOR]

The incorporation of cover crops into annual crop rotations is one practice that is used in the Mid-Atlantic United States to manage soil fertility, suppress weeds, and control erosion. Additionally, flowering cover crops have the potential to support beneficial insect communities, such as native bees. Because of the current declines in managed honey bee colonies, the conservation of native bee communities is critical to maintaining "free" pollination services. However, native bees are negatively affected by agricultural intensification and are also in decline across North America.We conducted two experiments to assess the potential of flowering cover crops to act as a conservation resource for native bees.We evaluated the effects of cover crop diversity and fall planting date on floral resource availability and visitation by native bees for overwintering flowering cover crop species commonly used in the Mid-Atlantic region. Cover crop species, crop rotation schedule, and plant diversity significantly influenced floral resource availability. Different cover crop species not only had different blooming phenologies and winter survival responses to planting date, but attracted unique bee communities. Flower density was the primary factor influencing frequency of bee visitation across cover crop diversity and fall planting date treatments. The results from these experiments will be useful for informing recommendations on the applied use of flowering cover crops for pollinator conservation purposes. [ABSTRACT FROM AUTHOR]

Demand for agricultural production systems that are both economically viable and environmentally conscious continues to increase. In recent years, reduced tillage systems, and grass and pasture rotations have been investigated to help maintain or improve soil quality, increase crop yield, and decrease labor requirements for production. However, documentation of the effects of reduced tillage, fescue rotation systems as well as other management practices, including pesticides, on pest damage and soil arthropod activity in peanut production for the Mid-Atlantic US region is still limited. Therefore, this project was implemented to assess impacts of fescue-based rotation systems on pests and other soil organisms when compared with cash crop rotation systems over four locations in eastern North Carolina. In addition, the effects of tillage (strip vs. conventional) and soil chlorpyrifos application on pod damage and soil-dwelling organisms were also evaluated. Soil arthropod populations were assessed by deploying pitfall traps containing 50% ethanol in each of the sampled plots. Results from the present study provide evidence that location significantly impacts pest damage and soil arthropod diversity in peanut fields. Cropping history also influenced arthropod diversity, with higher diversity in fescue compared with cash crop fields. Corn rootworm damage to pods was higher at one of our locations (Rocky Mount) compared with all others. Cropping history (fescue vs. cash crop) did not have an effect on rootworm damage, but increased numbers of hymenopterans, acarina, heteropterans, and collembolans in fescue compared with cash crop fields. Interestingly, there was an overall tendency for higher number of soil arthropods in traps placed in chlorpyrifos-treated plots compared with nontreated controls. [ABSTRACT FROM AUTHOR]

No-till practices are restoring and protecting soil health and are considered critical for achieving sustainability of global agriculture. Organic producers in the USA would like to no-till, but are concerned about managing weeds without tillage. In conventional agriculture, no-till improves weed management in diverse rotations when crops are arranged in 2-year intervals of cool season and warm season crops. A similar approach with organic rotations may enable producers to also accrue the weed management benefit of no-till in organic farming along with restoring soil health. Here, we review the benefits gained for weed management when a complex rotation is integrated with continuous no-till. The complex rotation included 3 years of a perennial legume and 6 years of annual crops arranged in 2-year intervals of warm season or cool season crops. The no-till, complex rotation can (1) reduce weed emergence 3- to 4-fold in some annual crops; (2) delay weed emergence 2 to 4 weeks; (3) reduce yield loss due to weed interference; (4) suppress invasion of dandelion into cropland; and (5) enhance soil restoration, improve nutrient cycling, and increase soil porosity. Furthermore, perennial red clover can be converted to no-till cropland with fall mowing; thus, organic producers can include a perennial legume in a no-till rotation. The complex rotation increases the impact of no-till on weed seed decay in soil and provides numerous opportunities for cover crops to replace tillage for controlling weeds. These benefits suppress weed growth and interference such that organic producers may be able to continuously no-till in their farming systems, thus accruing restoration of soil health and long-term sustainability gained with no-till. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Little information exists on the potential for N fertilizer application to corn (Zea mays L.) to affect N2O emissions during subsequent unfertilized crops in a rotation. To determine if N fertilizer application to corn affects N2O emissions during subsequent crops in rotation, we measured N2O emissions for 3 yr (2011-2013) in an Iowa, corn-soybean [Glycine max (L.) Merr.] rotation with three N fertilizer rates applied to corn (0 kg N ha-1, the recommended rate of 135 kg N ha-1, and a high rate of 225 kg N ha-1); soybean received no N fertilizer. We further investigated the potential for a winter cereal rye (Secalecereale L.) cover crop to interact with N fertilizer rate to affect N2O emissions from both crops. The cover crop did not consistently affect N2O emissions. Across all years and irrespective of cover crop, N fertilizer application above the recommended rate resulted in a 16% increase in mean N2O flux rate during the corn phase of the rotation. In 2 of the 3 yr, N fertilizer application to corn (0-225 kg N ha-1) did not affect mean N2O flux rates from the subsequent unfertilized soybean crop. However, in 1 yr after a drought, mean N2O flux rates from the soybean crops that received 135 and 225 kg N ha-1 N application in the corn year were 35 and 70% higher than those from the soybean crop that received no N application in the corn year. Our results are consistent with previous studies demonstrating that cover crop effects on N2O emissions are not easily generalizable. When N fertilizer affects N2O emissions during a subsequent unfertilized crop, it will be important to determine if total fertilizer-induced N2O emissions are altered or only spread across a greater period of time. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recent increases in corn (Zea mays L.) production in the U. S. Corn Belt have necessitated the conversion of rotations to continuous corn, and an increase in the frequency of tillage. The objective of this study was to assess the effect of rotation and tillage on soil physical and chemical properties in soils typical of Illinois. Sequences of continuous corn (CCC), 2-yr corn-soybean [Glycine max (L.) Merr.] (CS) rotation, 3-yr corn-soybean-wheat (Triticum aestivum L.) (CSW) rotation, and continuous soybean (SSS) were split into conventional tillage (CT) and no-till (NT) subplots at two Illinois sites. After 15 yr, bulk density (BD) under NT was 2.4% greater than under CT. Water aggregate stability (WAS) was 0.84 kg kg-1 under NT compared to 0.81 kg kg-1 under CT. Similarly, soil organic carbon (SOC) and total nitrogen (TN) were greater under NT than under CT with SOC values for 0 to 60 cm of 96.0 and 91.0 Mg ha-1 and TN values of 8.87 and 8.40 Mg ha-1 for NT and CT, respectively. Rotations affected WAS, TN, and K levels with WAS being greatest for the CSW rotation at 0.87 kg kg-1, decreasing with more soybean years (CS, 0.82 kg kg-1 and SSS, 0.79 kg kg-1). A similar pattern was detected for TN and exchangeable K. Results indicated that while the use of NT improved soil quality, long-term implementation of continuous corn had similar soil quality parameters to those found under a corn-soybean rotation. [ABSTRACT FROM AUTHOR]

The objectives of this study were to determine the effects of risk exposure on optimal N fertilizer rates for continuous corn (Zea mays L.), corn grown after cotton (Gossypium ssp.), and corn grown after soybean \Glycine max (L.) Merr.] and identify the optimal corn rotation for risk-averse corn producers. Data were collected from a 7-yr, corn-rotation, N-fertilizer experiment in Tennessee. Partial budgets were used to calculate net returns to N for corn grown after corn, corn grown after cotton, and corn grown after soybean. The flexible moment method was used for risk analysis, a unique application of this method that provides producers with information concerning traditional risk effects on decisions about crop rotations and N rates augmented by the effects of downside risk. Results from this study show rotating corn with cotton and soybean increased yields and net returns relative to continuous corn, but profit-maximizing N rates for corn were not greatly impacted by the crop planted in the previous year. Optimal N rates decreased for producers with more risk aversion, indicating that N fertilizer is a risk-increasing input. Downside risk was found for continuous corn and corn grown after soybean, increasing the risk premiums for these rotations above the risk premium for corn grown after cotton. Slightly to moderately risk-averse corn producers would prefer growing corn after soybean, but highly risk-averse producers would prefer rotating corn with cotton. Results provide corn producers with enhanced information about the effects of risk exposure on choices among corn rotations and N fertilizer rates. [ABSTRACT FROM AUTHOR]

Biowaste compost exploitation is a way of recovering agricultural soil fertility that in these last decades decreased up to a desertification limit. In order to test compost efficacy on crop yield and soil fertility, in the period 2011-2013 at COTIR experimental farm, a trial comparing different amounts of compost on two crop rotations was carried out. Crop rotations tested were durum wheat-sunflower-durum wheat and tomato-durum wheat-pepper. Results showed that the use of 40 t ha-1 of compost increased wheat grain yield and protein content if compared to control and mineral fertilised treatment. Compost application at 40 t ha-1 increased also yield of pepper in the first two harvest times, while during the third harvest, which included green and red berries, (the) yield was statistically different only if compared to control treatment. Moreover, compost improved soil fertility both in terms of organic matter and main nutritional elements, while a negative aspect of its use was the increase of soil electric conductivity, although no negative effect on crops yield were observed. [ABSTRACT FROM AUTHOR]

The paper examines the determinants of the adoption of land management practices and impact on crop production and household income. The study employed a multi stage sampling technique to select 100 respondents who were adopters of inorganic fertilizer, crop rotation and organic manure. Descriptive statistics, budgetary technique and multinomial logit were used to analyze the data collected from respondents. The gross margins for adopters of inorganic fertilizer, crop rotation and organic manure were ₦88690.6/ha, ₦55620/ha and ₦84130/ha, respectively (₦ is Naira, Nigeria currency; ₦1 equal $0.0065). Net incomes were ₦77252.6/ha, ₦44040/ha and ₦74506.6/ha. Rate of returns were 2.7, 1.8 and 3.3 for adopters of inorganic fertilizer, crop rotation and organic manure, respectively. The multinomial logit estimates indicated that education level and household size were significant determinants of adoption of fertilizer use while household size was the only determinant of the adoption of crop rotation. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Rotation experiments are intended to compare different sequences of crop (and possibly husbandry) combinations. To avoid the conclusions being dependent on a specific sequence of years, it is advantageous to phase the start of the experiment, with new replicates of the rotations starting in successive years. Once a complete cycle has taken place, comparisons can then be made between the rotations in every subsequent year. If sufficient resources are available to have more than one replicate in each year, it will be possible to do an interim analysis with the data from a single year. Otherwise meaningful analyses will need several years' data and the assumption, e.g., that higher order interactions can be ignored or that responses over years can be modeled by low-order polynomials. Other analysis complications are that the within-year variances may be unequal and that the correlation between observations on a plot may differ according to the distance in time between them. The old-fashioned method of analysis, feasible if the data are balanced, would be to do a repeated-measurements analysis of variance. A more recent, and more satisfactory, alternative is to do a mixed model analysis by residual (restricted) maximum likelihood estimation, possibly fitting a model to the between-year correlation structure. The issues are illustrated using data from the Woburn Ley-Arable Experiment. [ABSTRACT FROM AUTHOR]

This article characterizes the weed seedbank after a 12-yr rotation of cotton (Gossypium hirsutum L.)-tomato (Lycopersicon esculentum L.) under standard tillage (ST) and conservation tillage (CT) with and without cover crops in Five Points, CA, from 1999 to 2011. Treatment comparisons included standard tillage with no cover crop (STNO), standard tillage with cover crop (STCC), conservation tillage with no cover crop (CTNO), and conservation tillage with cover crop (CTCC). Weed density, by species, in each plot was assessed in 2003, 2006, and 2011. In 2011, soil cores were taken from each plot and seedlings that emerged from these cores were monitored in the greenhouse, counted by species, and the data were subjected to canonical discriminant analysis. Differences in weed densities were not consistent between CT and ST plots but they were generally greater in plots with cover crops than in those without, particularly in the CT system. The seedbank size was largest in the CTCC system. The weed seedbank community composition of this system was also distinctly different from the other systems. Shepherd's-purse (Capsella bursa-pastoris L. Medik.), black nightshade (Solanum nigrum L.), henbit (Lamium amplexicaule L.), and common chickweed (Stellaria media L. Vill.) were associated with the CTCC system. Barnyardgrass (Echinochloa crus-galli L. Beauv.) and horseweed (Conyza canadensis L. Cronq.) were associated with the CTNO system. Although differences in the aboveground weed densities were inconsistent between the tillage systems, the weed seedbank size was greater in the CT system and having a cover crop further increased the seedbank size. [ABSTRACT FROM AUTHOR]

Pea (Pisum sativum L.) is increasingly being rotated with wheat (Triticum aestivum L.) in Montana. Our objective was to compare economic net returns among wheat-only and pea-wheat systems during an established 4-yr crop rotation. The experimental design included three wheat-only (tilled fallow-wheat, no-till fallow-wheat, no-till continuous wheat) and three no-till pea-wheat (pea-wheat, pea brown manure-wheat, and pea forage-wheat) systems as main plots, and high and low available N rates as subplots. Net returns were calculated as the difference between market revenues and operation and input costs associated with machinery, seed and seed treatment, fertilizer, and pesticides. Gross returns for wheat were adjusted to reflect grain protein at "flat" and "sharp" discount/premium schedules based on historical Montana elevator schedules. Cumulative net returns were calculated for four scenarios including high and low available N rates and flat and sharp protein discount/premium schedules. Pea-wheat consistently had the greatest net returns among the six systems studied. Pea fallow-wheat systems exhibited greater economic stability across scenarios but had greater 4-yr returns (US$287 ha-1) than fallow-wheat systems only under the low N rate and sharp protein discount schedule scenario. We concluded that pea-wheat systems can reduce net return uncertainties relative to wheat-only systems under contrasting N fertility regimes, and variable wheat protein discount schedules in southwestern Montana. This implies that pea-wheat rotations, which protected wheat yield and/or protein levels under varying N fertility management, can reduce farmers' exposure to annual economic variability. [ABSTRACT FROM AUTHOR]

The need to intensify agricultural production due to a growing human population requires yield gaps to be closed. In 2009 and 2010, five management factors were assessed for their individual and cumulative contributions to reducing the corn (Zea mays L.) yield gap and yield components in a corn--soybean [Glycine max (L.) Merr.] rotation. Five management factors (plant population, transgenic insect resistance, fungicide containing strobilurin, P-S-Zn fertility, and N fertility) were evaluated. An incomplete factorial design with these factors resulted in 12 treatments, including two controls: high technology (HT) and standard technology (ST), comprising all five factors applied at the supplemental or the standard level, respectively. The HT control yielded 2.9 Mg ha-1 (2.12-3.50 Mg ha-1 across sites and years) more grain (28%) than the ST control, demonstrating the yield gap between traditional farm practice and attainable yield using available technologies. All management factors except plant population were necessary for reducing the yield gap. Fungicide and Bacillius thuringiensis gene (Bt) traits provided the greatest yield increases compared to the ST system. Averaged over sites and years, if each factor was withheld from the HT system, yield decreased by decreasing kernel number. Increased plant population reduced the yield gap when all other inputs were applied at the supplemental level. Kernel number was more significant for increasing yield than kernel weight. The yield contribution of each factor was greater when applied as part of a full complement of supplemental inputs than when added individually to the standard input system. [ABSTRACT FROM AUTHOR]

To allow for information on successional changes in phytodiversity over time and space, as well as information on differences between clones and treatments, phytodiversity was monitored on a poplar short rotation coppice plantation in Oberschwaben, Southwest Germany, in four consecutive years. The investigated plantation was divided into two core areas, one planted with poplar clone Max4, the other with Monviso; each core area was divided into two blocks with alternating treatments: (i) irrigation and fertilization; (ii) irrigation; and (iii) no treatment. All vascular plant species of the ground vegetation were recorded in 72 permanent sampling plots of 25 m2 each during vegetation periods using the Braun-Blanquet scale. Results showed that total number of species increased in first 2 years and declined after harvest of the SRC-trees. Total vegetation cover decreased during the 4 years of study. Especially for the two clones there was an opposed trend: grass layer had a high cover on Monviso plots, but low cover on Max4 plots; herb layer the very reverse. However, there was no significant difference between the three treatments compared within each year. Perennial species were dominating over all years, as well as light-demanding species, but their proportion decreased steadily. Our results confirm the conclusion of previous studies which indicate that plant community succession takes place in ground vegetation of SRC and imply that species composition is age-dependent. The selection of clones for SRC can influence ground vegetation; some floristic changes for example caused by different treatments may be visible only when monitored over a longer period of time. [ABSTRACT FROM AUTHOR]

Biofumigation is a sustainable method of soil management in cash crop rotations that can increase soil organic matter (SOM), moderate soil pH, suppress weeds and soilborne pathogens through glucosinolates (GSL), and increase water infiltration. This 2-year (2011-13) field study evaluated four different Brassica crops for their biofumigant potential in a chile pepper rotation system in southern New Mexico. The four cultivars included: three mustards (Brassica juncea 'Caliente 61', 'Caliente 199', and 'Pacific Gold') and one broccoli (Brassica oleracea var. botrytis 'Arcadia'). As a result of concerns that these mustards could be hosts for nematodes, a greenhouse study was conducted in the second year to evaluate the biofumigant crops for their southern root-knot nematode (Meloidogyne incognita, RKN) host suitability and their seedling establishment in the presence of RKN. In Year 1 (2011), conditions were ideal, which resulted in high mustard biomass production and, consequently, significantly higher SOM and lower pH than the bare soil control plots. However, there were no chile pepper yield differences among treatments. Conditions were much less favorable in Year 2 and the resultant poor biomass production did not cause an increase in SOM as seen in Year 1. In the RKN greenhouse study, broccoli was the least susceptible biofumigant crop. After one nematode generation (683 cumulative heat units), RKN populations were less than half of the original inoculum level on the broccoli. However, RKN populations increased in the presence of 'Caliente 61', 'Caliente 199', and 'Pacific Gold'. Overall, broccoli produced lower biomass and lower GSL concentrations than the mustard treatments but may be a valuable crop for growers with nematode issues because RKN populations decreased in its presence. Based on high biomass production and high GSL concentration, 'Caliente 199' showed the most potential as a biofumigant crop for southern New Mexico. [ABSTRACT FROM AUTHOR]

In this study, we assessed whether crop rotation with broccoli suppressed eggplant Verticillium wilt. In 6 trials of crop rotation in 5 fields from 2009 to 2013, broccoli rotation was coupled with postharvest residue incorporation before planting eggplant. Meta-analysis of the disease incidence data from all the trials revealed that the combined relative disease risk was 0.53 (95 % confidence interval 0.34-0.83). Thus, the disease incidence of eggplant in crop rotation with broccoli decreased to 53 % of that of eggplant without broccoli rotation. Browning of vascular tissue from Verticillium dahliae infection was observed in broccoli, but was limited to the roots and did not reach the aerial plant portion where V. dahliae forms microsclerotia. Estimation of V. dahliae population in soil using quantitative nested real-time polymerase chain reaction indicated that V. dahliae DNA copy number in soil samples tended to decrease owing to broccoli cultivation. These results suggest that broccoli root could act as a 'decoy' that traps V. dahliae in soil. Further studies are necessary to elucidate the mechanisms of disease suppression; this is the first report that broccoli cultivation and subsequent incorporation of residue into the soil suppresses Verticillium wilt of eggplant. [ABSTRACT FROM AUTHOR]

Conservation tillage and diversified crop rotations have been suggested as appropriate alternative soil management systems to sustain soil quality. The purpose of this study was to quantify the effect of implementing three crop rotations (R2–R4) on soil structural changes and the “productivity function” of soil. R2 is a winter-dominated crop rotation (winter wheat was the main crop) with straw residues incorporated. R3 is a mix of winter and spring crops with straw residues removed. R4 is the same mix of crops as in R3, but with straw residues incorporated. Three tillage systems were used for each rotation: mouldboard ploughing to a depth of 20 cm (MP); harrowing to a depth of 8–10 cm (H); and direct drilling (D) at two experimental sites with a sandy loam soil and different water budgets in Denmark. The Muencheberg soil quality rating (M-SQR) method and simpler soil quality indices (i.e. visual evaluation of soil structure (VESS), overall visual structure (OVS) and overall soil structure (OSS)) were employed to differentiate the effects of these alternative management practices on soil structural quality and relative crop yield (RY). A Pearson correlation was also employed to find the correlation between the soil quality indices and relative crop yield. Relevant soil properties for calculating the soil quality indices were measured or obtained from previous publications. Crop rotation affected the soil structure and RY. The winter-dominated crop rotation (R2) resulted in the poorest soil structural quality and produced the lowest RY compared to the mixed rotations (R3 and R4). Tillage systems clearly influenced the soil quality and RY. The MP resulted in the best soil structural quality, and consequently the highest RY compared with both the reduced tillage treatments. Significant correlations were found in most cases between soil quality indices (including M-SQR) and RY. This highlights the influence of soil quality (as measured by the selected indicators) – and soil structure in particular – on crop yield potential. [ABSTRACT FROM AUTHOR]

Horizontal and vertical distribution of the reniform nematode, Rotylenchulus reniformis Linford and Oliveira, was examined over a 3-yr period in Mississippi cotton soils. Two naturally infested cotton fields (8.1 ha each) were examined to determine the effects of continuous cotton production and a cotton-corn rotation system on the nematode population dynamics in two different seasons (spring and fall). Sixteen grids (0.4 ha) were established in each field. Both fields were grid-mapped with 16 points on 0.4-ha grids using a Global Positioning System (GPS). A single soil core, 5.08-cm diameter x 121.92 cm deep, was collected from each grid intersection and divided into 8 sample depths. Reniform nematodes were found at each of 16 geo-referenced sample sites and in all of the eight sampling depths. The number of reniform nematodes varied from 10 to 2,500 per 100 cm³ soil across sample sites. The nematode population appeared to have a non-clustered horizontal distribution across both the continuous cotton production and cotton-corn rotation fields. Reniform nematode numbers also differed by season. The sampling time and depth were associated with nematode density. In the continuous cotton production field, nematode numbers found in the upper soil profile were higher in the fall than in the spring. In the cottoncorn rotation field after corn was planted, more nematodes were recovered in the lower soil profiles in the fall. Corn and cotton rotations affected both nematode numbers and distribution in relation to soil depth. The recovery of reniform nematodes deep in the soil profile may help explain why this nematode is capable of reaching high levels in the soil after a single year rotation with corn. [ABSTRACT FROM AUTHOR]

The absorption and partitioning of N is determined by its availability and demand during the various phenological stages of the crop. In two experiments conducted in rainfed areas of the Mediterranean climate region of central Chile, legume-wheat (Triticum aestivum L.) rotations were compared to oat (Avena sativa L.)-wheat systems (with and without applications of N fertilizer). The objective was to assess the contribution of legumes to the availability of soil N and N uptake by the wheat crop following grain legumes. N mineralization and uptake, N use efficiency (NUE), and N uptake efficiency (NUpE) by wheat were evaluated at different phenological stages in 2010. Synchronization existed between accumulated soil N mineralization and N uptake by the wheat. N uptake by wheat was higher in Experiment II (Andean foothill) than in Experiment I (interior dryland). Grain yields after legumes ranged 60-110% and 72-103% of yields in the fertilized cereal rotation (oat-wheat) in Experiments I and II, respectively. There was high correlation between soil N availability vs. grain yield (R² = 0.84 and 0.64) and N uptake vs. grain yield (R² = 0.55 and 0.64) for Experiments I and II, respectively. Rotations with lupine (Lupinus spp.) and field peas (Pisum sativum L.) showed high NUE and NUpE in Experiment I, and Experiment II in pea. The lowest NUE was after oats with N fertilizers. It is concluded that wheat cultivated in both agro-ecological areas after grain legumes or green manure was more efficient in N uptake and use than cereal, especially when the latter was fertilized. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We studied the resident (16S rDNA) and the active (16S rRNA) members of soil archaeal and bacterial communities during rice plant development by sampling three growth stages (vegetative, reproductive and maturity) under field conditions. Additionally, the microbial community was investigated in two non-flooded fields (unplanted, cultivated with upland maize) in order to monitor the reaction of the microbial communities to non-flooded, dry conditions. The abundance of Bacteria and Archaea was monitored by quantitative PCR showing an increase in 16S rDNA during reproductive stage and stable 16S rRNA copies throughout the growth season. Community profiling by T-RFLP indicated a relatively stable composition during rice plant growth whereas pyrosequencing revealed minor changes in relative abundance of a few bacterial groups. Comparison of the two non-flooded fields with flooded rice fields showed that the community composition of the Bacteria was slightly different, while that of the Archaea was almost the same. Only the relative abundance of Methanosarcinaceae and Soil Crenarchaeotic Group increased in non-flooded vs. flooded soil. The abundance of bacterial and archaeal 16S rDNA copies was highest in flooded rice fields, followed by non-flooded maize and unplanted fields. However, the abundance of ribosomal RNA (active microbes) was similar indicating maintenance of a high level of ribosomal RNA under the non-flooded conditions, which were unfavorable for anaerobic bacteria and methanogenic archaea. This maintenance possibly serves as preparedness for activity when conditions improve. In summary, the analyses showed that the bacterial and archaeal communities inhabiting Philippine rice field soil were relatively stable over the season but reacted upon change in field management. [ABSTRACT FROM AUTHOR]

Most of the plants employed to remove metals from contaminated soils are annuals and have a seed-to-seed life cycle of a few months, usually over spring and summer. Consequently, for most of the year, fields are not actively cleaned but are completely bare and subject to erosion by water and wind. The objective of this study was to evaluate the benefits of using Lupinus albus as a winter crop in a rotation sequence with a summer crop ideally selected for phytoextraction, such as industrial hemp. Lupin plants were grown in two alkaline soil plots (heavy metal-contaminated and uncontaminated) of approximately 400 m 2 each after the cultivation and harvest of industrial hemp. A smaller-scale parallel pot experiment was also performed to better understand the lupin behavior in increasing concentrations of Cd, Cu, Ni and Zn. White lupin grew well in alkaline conditions, covering the soil during the winter season. In few months plants were approximately 40-50 cm high in both control and contaminated plots. In fields where the bioavailable fraction of metals was low (less than 12%), plants showed a high tolerance to these contaminants. However, their growth was affected in some pot treatments in which the concentrations of assimilable Cu, Zn and Ni were higher, ranging from approximately 40-70% of the total concentrations. The lupin's ability to absorb heavy metals and translocate them to shoots was negligible with respect to the magnitude of contamination, suggesting that this plant is not suitable for extending the period of phytoextraction. However, it is entirely exploitable as green manure, avoiding the application of chemical amendments during phytoremediation. In addition, in polluted fields, white lupin cultivation increased the soil concentration of live bacteria and the bioavailable percentage of metals. On average live bacteria counts per gram of soil were 65 × 10 6 ± 18 × 10 6 and 99 × 10 6 ± 22*10 6 before and after cultivation, respectively. The percentages of bioavailable Cu, Pb, Ni, Zn and Cr, which were 5.7 ± 0.7, 5.3 ± 1.7, 1.2 ± 0.1, 12 ± 1.5 and 0.1 ± 0.02%, respectively, before lupin growth, increased to 9.6 ± 1.6, 7 ± 2, 2 ± 0.3, 14 ± 1.5 and 0.1 ± 0.02% after lupin harvest. On the whole, our results indicate that the winter cultivation of white lupin in sequence with a metal-accumulator summer crop can improve the recovery of soil quality during the phytoextraction period. It improves the safety of the area, limiting additional ecological and human health problems, and enhances soil health by avoiding the use of chemical amendments and by increasing the levels of viable microorganisms. [ABSTRACT FROM AUTHOR]

There are many environmental benefits to incorporating cover crops into crop rotations, such as their potential to decrease soil erosion, reduce nitrate (NO3) leaching, and increase soil organic matter. Some of these benefits impact other agroecosystem processes, such as greenhouse gas emissions. In particular, there is not a consensus in the literature regarding the effect of cover crops on nitrous oxide (N2O) emissions. Compared to site-specific studies, meta-analysis can provide a more general investigation into these effects. Twenty-six peer-reviewed articles including 106 observations of cover crop effects on N2O emissions from the soil surface were analyzed according to their response ratio, the natural log of the N2O flux with a cover crop divided by the N2O flux without a cover crop (LRR). Forty percent of the observations had negative LRRs, indicating a cover crop treatment which decreased N2O, while 60% had positive LRRs indicating a cover crop treatment which increased N2O. There was a significant interaction between N rate and the type of cover crop where legumes had higher LRRs at lower N rates than nonlegume species. When cover crop residues were incorporated into the soil, LRRs were significantly higher than those where residue was not incorporated. Geographies with higher total precipitation and variability in precipitation tended to produce higher LRRs. Finally, data points measured during cover crop decomposition had large positive LRRs and were larger than those measured when the cover crop was alive. In contrast, those data points measuring for a full year had LRRs close to zero, indicating that there was a balance between periods when cover crops increased N2O and periods when cover crops decreased emissions. Therefore, N2O measurements over the entire year may be needed to determine the net effect of cover crops on N2O. The data included in this meta-analysis indicate some overarching crop management practices that reduce direct N2O emissions from the soil surface, such as no soil incorporation of residues and use of non-legume cover crop species. However, our results demonstrate that cover crops do not always reduce direct N2O emissions from the soil surface in the short term and that more work is needed to understand the full global warming potential of cover crop management. [ABSTRACT FROM AUTHOR]

The winter wheat (Triticum aestivum L.)/summer fallow rotation typically practiced in the intermediate precipitation zone (300 to 450 mm [12 to 18 in]) of the inland Pacific Northwest has proven to be economically stable for producers in this region. However, multiple tillage operations are used to control weeds and retain seed-zone soil moisture, which disturbs the soil and makes it prone to substantial erosion. Alternatives to this conventional disturbance tillage (DT) system include either no-tillage (NT) or minimum tillage (MT) in combination with increasing cropping intensity. The objective of this study was to compare runoff, soil erosion, crop residue, and yield productivity resulting from NT, and DT, or MT. Small collectors and flumes were used to quantify runoff and soil erosion from small drainages and slopes in three different experiments near Pendleton, Oregon. The first experiment included two neighboring drainages: one farmed using DT with a two-year crop rotation over eight years (2001 to 2008) and the other NT with a four-year crop rotation (2001 to 2008).The second experiment comprised a hillslope planted to different crops using NT over eight years (1998 to 2005) and MT over three years (2006 to 2008). The third experiment was situated in a shallow draw in which NT and MT with a four-year (2004 to 2008) crop rotation was compared. Runoff measured in flumes was substantially influenced by tillage method in the order of DT > NT in a ratio of 10:1 at the first site. At the second site, NT produced no runoff compared to 1.6 mm y-1 (0.06 in yr-1) from MT. Soil erosion was found to be DT > NT in a ratio of 5:1 at the first site and 2:1 for the second site. For small collectors the differences were significant: runoff was DT > NT in a ratio of 47:1 for the first site, and MT > NT in a ratio of 2:1 for the third site. Winter wheat yields did not differ significantly among NT, DT, and MT. Broader acceptance of NT cropping systems in the intermediate precipitation zone of this region would substantially decrease soil losses from farm fields and improve downstream water quality. [ABSTRACT FROM AUTHOR]

In response to changing market dynamics, the discovery of new herbicides has declined significantly over the past few decades and has only seen a modest upsurge in recent years. Nevertheless, the few introductions have proven to be interesting and have brought useful innovation to the market. In addition, herbicide-tolerant or herbicide-resistant crop technologies have allowed the use of existing nonselective herbicides to be extended into crops. An increasing and now major challenge is being posed by the inexorable increase in biotypes of weeds that are resistant to herbicides. This problem is now at a level that threatens future agricultural productivity and needs to be better understood. If herbicides are to remain sustainable, then it is a must that we adopt diversity in crop rotation and herbicide use as well as increase the use of nonchemical measures to control weeds. Nevertheless, despite the difficulties posed by resistant weeds and increased regulatory hurdles, new screening tools promise to provide an upsurge of potential herbicide leads. Our industry urgently needs to supply agriculture with new, effective resistance-breaking herbicides along with strategies to sustain their utility. [ABSTRACT FROM AUTHOR]