Years Of Crop Rotation Research Articles

Maize, Peanut, and Millet Rotations Improve Crop Yields by Altering the Microbial Community and Chemistry of Sandy Saline-Alkaline Soils.

Crop rotation increases crop yield, improves soil health, and reduces plant disease. However, few studies were conducted on the use of intensive cropping patterns to improve the microenvironment of saline soils. The present study thoroughly evaluated the impact of a three-year maize-peanut-millet crop rotation pattern on the crop yield. The rhizosphere soil of the crop was collected at maturity to assess the effects of crop rotation on the composition and function of microbial communities in different tillage layers (0-20 cm and 20-40 cm) of sandy saline-alkaline soils. After three years of crop rotation, the maize yield and economic benefits rose by an average of 32.07% and 22.25%, respectively, while output/input grew by 10.26%. The pH of the 0-40 cm tillage layer of saline-alkaline soils decreased by 2.36%, organic matter rose by 13.44%-15.84%, and soil-available nutrients of the 0-20 cm tillage layer increased by 11.94%-69.14%. As compared to continuous cropping, crop rotation boosted soil nitrogen and phosphorus metabolism capacity by 8.61%-88.65%. Enrichment of Actinobacteria and Basidiomycota increased crop yield. Crop rotation increases microbial community richness while decreasing diversity. The increase in abundance can diminish competitive relationships between species, boost synergistic capabilities, alter bacterial and fungal community structure, and enhance microbial community function, all of which elevate crop yields. The obtained insights can contribute to achieving optimal management of intensive cultivation patterns and green sustainable development.

Influence of by-products under different methods of soil cultivation on the yield of winter rape in the Western Forest-Steppe

The absence of a clear position on the application of a particular method of basic tillage and the use of post-harvest residues in crop rotation draws attention to the minimisation of tillage. Therefore, the need to substantiate and develop efficient energy-saving tillage technologies and the use of by-products in crop rotation is quite important and remains relevant. The aim of the research is to study the impact of by-products and soil cultivation, which will create optimal conditions for the development of winter rape in the Western Forest-Steppe of Ukraine. The research was carried out during 3 rotations of 4 crop rotation in a stationary field experiment of the Institute of Agriculture of Western Polissya of the National Academy of Agrarian Sciences in 2009-2020. Against the background of soil cultivation, including ploughing, disc cultivation to a depth of 10-12 and 6-8 cm, two methods of using crop residues of crop rotation were studied - diversion and use as fertiliser with the addition of compensatory nitrogen in the amount of N10 per 1 tonne. The results showed that when growing winter rape with the removal of the predecessor straw from the field during ploughing to a depth of 20-22 cm and disc cultivation to a depth of 10-12 and 6-8 cm, the soil density at a depth of 0-10 cm was 1.22-1.28, 1.23-1.28 and 1.23-1.35 g/cm³, respectively, and at a depth of 10-20 cm – 1.26-1.30, 1.30-1.35 and 1.32-1.36 g/cm³. The use of straw as an organic fertiliser led to a decrease in the bulk mass of all the studied soil layers under any method of treatment, but at the same time contributed to an increase in the number of weeds, which increased with a decrease in the depth of treatment. On average, over the three years of crop rotation, the seed yields for ploughing by 20-22 cm, disking by 10-12 cm and disking by 6-8 cm against the background of straw alienation were 2.91, 2.83 and 2.59 t/ha, respectively, and for incorporating it into the soil – 3.04, 2.88 and 2.72 t/ha. As noted in the studies, tillage and fertilisation using non-commodity crop residues increase the soil protection effect, significantly reduce the negative impact of weeds in crops, improve soil fertility and increase the productivity of crops in the rotation

Soil Chemical Properties as Affected by Six Crop Rotation Sequences and Four Residue Levels

ABSTRACT Crop rotations with residue incorporation can be beneficial to the sustainability of agriculture, however as long-term studies are required to determine effects on soil properties, farmers usually don’t practice crop rotations. The objective of this study was to evaluate the effects of crop rotations with residue incorporation (0%, 50%, 100%, and 200%) on soil chemical properties of a volcanic soil after 4 years of cultivation. The evaluated rotations were canola (Brassica napus L.)-bread wheat (Triticum aestivum L.), canola-durum wheat (Triticum turgidum L.), canola-corn (Zea mays L.), bean (Phaseolus vulgaris L.)-bread wheat, bean-durum wheat, and bean-corn. The experiment consisted of six crop rotations, four levels of residue incorporation, and four replicates, analyzed as split-plot design. Samples were taken from the topsoil, and the following soil chemical properties were evaluated: pH, organic matter, electrical conductivity, nitrogen (N), phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), aluminum (Al), and sulfur (S). The results showed that crop rotations affected all the chemical properties evaluated, whereas the level of residue incorporation only affected the concentrations of exchangeable Mg and K. Most of the evaluated crops rotations had beneficial effects on the soil properties. The canola-durum wheat crop rotation recorded the lowest values in OM, available N and the exchangeable Ca, Mg, and Na. Exchangeable Mg and K had a directly proportional relationship with the level of residue incorporation. In conclusion, the incorporation of residues in different doses during 4 years of crop rotation in this volcanic soil had little effect on its chemical properties.

Deciphering the role of particulate organic matter in soil nitrogen transformation in rice–rapeseed and rice–wheat rotation systems

Crop rotation affects the decomposition of soil organic matter (SOM) and thereby alter the composition of SOM fractions. It remains unclear how different SOM fractions impact soil nitrogen (N) transformation in various rotation systems. The aim of this study was to ascertain the role of particulate organic matter (POM)-a labile SOM fraction-in soil N transformation under various crop rotations. A paired plot experiment was conducted under two common cropping patterns, i.e., rice–rapeseed rotation (RR) vs. rice–wheat rotation (RW). Soil chemical composition and organic matter fraction before rice transplanting were compared between RR and RW systems after four years of crop rotations (2017–2021). With the same N inputs, the rice yield and N uptake under RR were 16.4 % and 13.2 % higher than those under RW, respectively. Compared with RW, RR resulted in higher carbon (C) and N contents in soil POM, despite minimal differences in total SOM. A larger potentially mineralizable N pool and a higher N mineralization rate occurred under RR than under RW, based on the results of soil net mineralization experiment. When POM was incubated alone, its contribution to potentially mineralizable N was 65.1 % and 61.3 % in RR and RW soils, respectively. Infrared spectroscopy revealed that in contrast with RW, RR promoted the accumulation of organic matter with high bioavailability (e.g., amides, carbohydrates, polysaccharides) in soil POM. This might be responsible for the higher gross mineralization and nitrification rates but lower gross immobilization rate under RR than under RW. Consequently, RR not only increased the contents of POMC and POMN but also improved the quality of POM fraction in soils. Findings of the present study demonstrate that POM plays a distinct role in soil N mineralization in various rotation systems. The discrepancy in POM content and composition resulting from various crop rotations leads to differences in soil N mineralization, which in turn affects the N supply and rice yield.

Mapping crop rotation by satellite-based data fusion in Southern Brazil

Crop monitoring is a key process for agricultural management and policy making linked to food security and sustainability. The spatio-temporal assessment of crop-specific management is essential for mapping crop rotation at field-scale. The aims of this study were to generate a satellite-based data fusion approach for mapping crop rotation at field-scale and generating analyses of crop rotation patterns among different mesoregions, examining the impact of environmental factors on crop yields, within the Rio Grande do Sul, southern Brazil. Within this geographical region, soybeans (Glycine max (L.) Merr.), corn (Zea mays L.), and rice (Oryza sativa L.) are the major grain crops of the state. We have utilized a satellite-based data fusion crop type classification and mapping to extract spatial crop features during four growing seasons (2017–2021), associated to field boundary delineation to generate the crop rotation database. This database showed current crop rotation practices within the study region, highlighting continuous soybean (monocrop), and three soybeans with one corn year rotation as the most frequent in the state. Midwestern and Northwest mesoregions presented the highest mean municipality values of continuous crop with 76% and 61%, respectively. Crop rotation patterns in Porto Alegre metropolitan, Southwest, and Southern mesoregions showed soybean-rice rotation, but with a trend of increases in soybean area in detriment to rice in lowlands. Crop rotation effects on yield for soybeans varied from 20 up to 65% depending on the regions and years of crop rotation. Other crop rotation effects in the crop yields were not significant at the municipality level. Crop rotation showed more significant benefits for soybean yields in warm and wet climate, with higher bulk density and lower soil organic carbon. Lastly, this study presents the first crop rotation map layer for the entire state of Rio Grande do Sul, southern Brazil, serving as a foundation for the creation of similar database for other states in the country and around the globe.

Lasting effect of Urochloa brizantha on a common bean-wheat-maize rotation in a medium-term no-till system

Grass intercropping under no-till is an option to increase crop residues on the soil surface and crop diversity. Urochloa spp. is frequently selected for intercropping to improve land use and agricultural production because of its high residue production, slow residue decomposition, as well as its vigorous, abundant, and deep root system. However, the effects of intercropping Urochloa and maize, especially the effects of Urochloa residues, on subsequent crops in rotation have not been established. To address this knowledge gap, a field experiment was carried out over 5 years (from 2014 to 2018) comprising 2 years of maize monocropping or intercropping and 3 years of crop rotation (common bean-wheat-common bean-wheat-maize). We evaluated the medium-term effects of monocropped maize or maize intercropped with Urochloa brizantha on soil fertility and the development, yields, and grain nutrient accumulation of subsequent common bean, wheat, and maize crops. The cultivation of U. brizantha in the intercropping system improved soil fertility over at least 4 years, with increases in soil pH; soil organic matter (SOM); phosphorus (P); exchangeable potassium (K), calcium (Ca), and magnesium (Mg); sulfur (S–SO42−); cation exchange capacity (CEC); and base saturation (BS) at all soil depths. The benefits of U. brizantha extended to root dry matter and distribution; 70–77% of the total roots were concentrated within a soil depth of 0.0–0.2 m. The intercropping system improved the root dry matter mass, yield components, and grain yields of subsequent common bean, wheat, and maize crops in all cultivation years. These findings indicate that intercropping maize and U. brizantha provides medium-term benefits for subsequent common bean, wheat, and maize crops, and improves nutrient cycling to increase soil P; exchangeable K, Ca, and Mg; S–SO42−; and organic matter content.

Crop rotation significantly influences the composition of soil, rhizosphere, and root microbiota in canola (Brassica napus L.)

BackgroundCrop rotation is an agronomic practice that is known to enhance productivity and yield, and decrease pest and disease pressure. Economic and other factors have increased the frequency of certain crops, including canola, with unknown effects on the below ground microbial communities that impact plant health and performance. This study investigated the effect of 12 years of crop rotation including canola-wheat; canola-pea-barley; and unrotated canola across three geographic sites in Western Canada with diverse soil types and environmental conditions. To provide data on mature, established crop rotation strategies, root exudate profiles, soil nutrient fluxes, and bacterial and fungal microbial community profiles were determined at the flowering stage in the final two (canola) years of the 12-year rotations.ResultsAfter 12 years of rotation, nutrient fluxes were affected in the soil in an inconsistent manner, with K, NO3, Mg, Ca, P, and Fe fluxes variably impacted by rotation depending on the year and site of sampling. As expected, rotation positively influenced yield and oil content, and decreased disease pressure from Leptosphaeria and Alternaria. In two of the three sites, root exudate profiles were significantly influenced by crop rotation. Bacterial soil, root, and rhizosphere communities were less impacted by crop rotation than the fungal communities. Fungal sequences that were associated with specific rotation strategies were identified in the bulk soil, and included known fungal pathogens in the canola-only strategy. Two closely related fungal sequences identified as Olpidium brassicae were extremely abundant at all sites in both years. One of these sequences was observed uniquely at a single site and was significantly associated with monocropped canola; moreover, its abundance correlated negatively with yield in both years.ConclusionsLong-term canola monoculture affected root exudate profiles and soil nutrient fluxes differently in the three geographic locations. Bacterial communities were less impacted by rotation compared to the fungal communities, which consistently exhibited changes in composition in all ecological niches at all sites, in both years. Fungal sequences identified as O. brassicae were highly abundant at all sites, one of which was strongly associated with canola monoculture. Soil management decisions should include consideration of the effects on the microbial ecosystems associated with the plants in order to inform best management practices.

Biodiversity of the microbiome as an indicator of phytomeliorative soil transformation

40% of the territory of Western Siberia is occupied by solonetzes, used mainly for growing forage grasses. The phytomeliorative effect of yellow sweet clover (cultivated in crop rotation at the Siberian Federal Research Center of Agrobiotechnologies (SFSCA) of the Russian Academy of Sciences (RAS) for 31 years), as well as post crop rotation grassing with a mixture of brome and alfalfa (the mixture was sown after twenty years of crop rotation) on the microflora of medium solonetz was studied. It is shown that the cultivation of phytomeliorants has led to an increase in the representation of classes and orders of bacteria in the microbiome of the medium solonetz, associated with nitrogen fixation and mineralization activity of the soil in relation to nitrogen-containing substances. In the post crop rotation grassing variant, a low bacterization of the soil with Verrucomicrobia and a high, as in virgin soil, Acidobacteria were found.

Soil properties and crop yields as influenced by the frequency of straw incorporation in rape-wheat-triticale rotation

Straw, particularly cereal straw, is a valuable by-product of crop production, which can be used for various purposes, e.g. as livestock feed and bedding or for making fuels, however it should primarily be retained on farmland in order to prevent soil organic matter (SOM) losses and thus to maintain or improve soil quality. The aim of this study was to analyze effects of the frequency of crop residues (straw) incorporation into the soil on the content of soil organic matter and on crop yields. There were the following experimental treatments: SR – straw of all crop in the rotation removed, S1 – straw of one crop per rotation incorporated, S2 – straw of two crops in the rotation incorporated, and S3 – straw of three crops incorporated into the soil (loamy sand). After 21 years of crop rotation with straw removal (SR) the SOM level in the soil slightly decreased to 14.4 g∙kg –1 soil DM, compared to that in 1997 (14.6 g∙kg –1). However, when straw of one crop (rape) per rotation was incorporated (S1) the content of SOM increased to 15.0 g∙kg -1 soil DM, and to 15.6 and 16.0 g∙kg –1 in S2 and S3 treatments respectively. Straw retention had also a beneficial effect on the content of labile fractions of SOM (hot water extractable C and N). Grain yields and yield components of wheat and triticale, and seed yields of rape in the SR treatment were not significantly different from those obtained in S1, S2 and S3 treatments.

Evaluation of Tillage Methods under Rainfed Cultivation of Cotton-Pulses Crop Rotation

Aims: To evaluate the effect of tillage methods on soil moisture storage, grain yield, economics and rain water use efficiency in semi-arid region
 Study Design: Four tillage methods viz. conventional tillage, Rotovator ploughing + chisel ploughing, chisel ploughing + tiller ploughing, conservation tillage (Minimum tillage with retention of crop residue) at different time of ploughing.
 Place and Duration of Study: Kovilpatti, a representative location of semi-arid regions of Southern Tamil Nadu. This study was conducted from 2015 to 2021 with the alternate years of crop rotation of cotton and greengram.
 Methodology: The field experiments were in cotton and greengram in black soil under rain fed situations. Soil samples were collected at different depths to assess the soil moisture storage. Yield was recorded and cost of cultivation was worked out. Rainwater used for obtaining higher yield was calculated. .
 Results: Soil moisture storage in subsurface soil layers was higher in conservation methods of tillage followed by rotatvator and chisel ploughing method. For both crops, Rotovator plough followed by chisel plough recorded the higher rain water use efficiency, yield and net return.
 Conclusion: This study clearly indicated that Rotovator ploughing once followed by chisel ploughing once could be adopted as a promising strategy to retain soil water availability and boost crop productivity in semiarid regions of Tamil Nadu.

Strategic level of agrocenoses state management

The aim of the work is to develop a theoretical basis for solving the problem of managing the state of agrocenoses, which contain crops of the main crop and weeds. The solution to this problem is aimed at eliminating the limitations of the existing paradigm of separate management of the state of crops and weeds. The application of mineral fertilizers simultaneously stimulates the growth and development of plants, crops and weeds, and herbicide treatments simultaneously suppress the growth of both crop plants and weeds. As a result, this leads to significant crop losses and overconsumption of fertilizers and herbicides. The proposed theory and methodology is based on taking into account the relationship between the state of crops and weeds, and their overall effect on the content of nutrients in the soil. For this, a system of mathematical models has been proposed, in which these relationships and yield losses are taken into account when the parameters of the chemical state of the soil deviate from the optimal values for crop rotation and from the effect of herbicide treatments on crop sowing. The result of solving the problem is the optimal strategies for the introduction of mineral fertilizers, ameliorants and herbicides by years of crop rotation. These strategies ensure that yield losses are minimized for all crops, rotation and agrochemical consumption. They are the main tool for planning agricultural technologies and standardizing technological operations carried out for individual years of crop rotation. The results obtained are new, since such tools are currently lacking.

Strategic level of agrocenoses state management

The aim of the work is to develop a theoretical basis for solving the problem of managing the state of agrocenoses, which contain crops of the main crop and weeds. The solution to this problem is aimed at eliminating the limitations of the existing paradigm of separate management of the state of crops and weeds. The proposed theory and methodology is based on taking into account the relationship between the state of crops and weeds, and their overall effect on the content of nutrients in the soil. For this, a system of mathematical models has been proposed, in which these relationships and yield losses are taken into account when the parameters of the chemical state of the soil deviate from the optimal values for crop rotation and from the effect of herbicide treatments on crop sowing. The result of solving the problem is the optimal strategies for the introduction of mineral fertilizers, ameliorants and herbicides by years of crop rotation. These strategies ensure that yield losses are minimized for all crops, rotation and agrochemical consumption. The results obtained are new, since such tools are currently lacking.

Fifteen years of crop rotation combined with straw management alters the nitrogen supply capacity of upland-paddy soil

Straw return affects the soil N supply; however, the mechanisms underlying the effects of different straw types and substance additions on soil N availability remain elusive. This study compared net N mineralization (NNM) in soils with various straw management histories under rotations rice-fallow (RF), rice-wheat (RW) and rice-potato with straw mulch (RP) during 2003–2017. The soils were then subjected to four substrate additions, including the no-substrate control, +N [(NH4)2SO4, 0.2 mg N kg−1 dry soil], +G (glucose, 0.6 mg C kg−1 dry soil) and +G+N (both). The responses of the soil NNM to substrate additions varied depending on the soils’ different straw histories. The direction of NNM was affected by substrate addition, but the magnitude depended on crop rotation and straw management. The NNM in the +G treatment ranged from 15.5 to 71.5 mg kg−1 in the soils with various straw histories, with RW and RP having 299% and 366% greater NNM than RF, respectively. Conversely, the addition of +N and +G+N decreased the soil NNM significantly in the soil with RW and RP straw histories, being 70~75% and 28~39% lower in the +N and +G+N treatments, respectively, than in the soil without straw history (RF). In addition, long-term straw return (RP and RW) significantly increased the soil ammonium N, amino acid N, and microbial biomass C and extracellular enzyme activity, while the addition of N and C substrates altered the decomposition of soil organic N. The long-term straw history also affected the soil bacterial community and formed a significant grouping compared to RF. In general, the soil from RF was dominated by heterotrophic bacteria such as Actinobacteria, Bacteroidetes and Proteobacteria, while the soils of RP and RW were mainly Firmicutes involved in straw glycolysis and part of Proteobacteria involved in N metabolism. Adding inorganic N altered bacteria in Proteobacteria, and the relative abundance of Proteobacteria had a negative relationship with the concentration of available N, indicating that bacteria induced by exogenous N were not involved in inherent N mineralization in soil. The addition of glucose enhanced the bacterial communities involved in N mineralization. The results imply that the soil N supply capability was enhanced with straw history under N deficiency and that an excess supply of N fertilizers was immobilized to minimize leaching losses.

Different crop rotation systems change the rhizosphere bacterial community structure of Astragalus membranaceus (Fisch) Bge. var. mongholicus (Bge.) Hsiao

Continuous cropping obstacles often lead to a decline in the quality and yield of traditional Chinese medicine plants. Crop rotation effectively alleviates the obstacles of continuous cropping. However, there are few studies on the rotation of traditional Chinese medicine crops. Astragalus membranaceus (Fisch) Bge. var. mongholicus (Bge.) Hsiao (A. mongholicus) is a commonly used traditional Chinese medicine. The present study investigates the growth of A. mongholicus and its associated soil microbiome and physicochemical properties under different crop rotation regimes in a field and pot experiment. The 16S rRNA gene high throughput sequencing was used to compare the composition and diversity of rhizosphere, bulk soil and endosphere bacterial communities of A. mongholicus after 5 years of crop rotation. Crop rotation with Avena sativa L, significantly increased the growth of A. mongholicus and elevated soil organic matter, total nitrogen, total phosphorus and available potassium contents. Crop rotation increased the bacterial community diversity in the rhizosphere of A. mongholicus and abundance of some beneficial bacteria, such as Clostridia, Rubrobacterales and Micromonosporales. The composition of the rhizosphere bacterial community differed between sampling times and depending on crop rotation. Briefly, crop rotation with Avena sativa L was beneficial to soil quality and A. mongholicus growth, and it is a good option to alleviate A. mongholicus continuous cropping obstacles.

Long term impact of different tillage systems on carbon pools and stocks, soil bulk density, aggregation and nutrients: A field meta-analysis

Intensive tillage frequently has adverse impact on soil physical quality and soil organic carbon stocks in temperate regions. A consequence of this has been a reduction in crop production over the years demonstrating the necessity of effective and sustainable agriculture. This study aimed to evaluate soil organic carbon (SOC) storage and pools, soil bulk density, aggregation and nutrient availability under different tillage systems (no-tillage, chisel and conventional tillage), based on a long field experiment. After 10 years of crop rotation, in 0–30 cm soil depth, no-tillage system had higher total organic carbon over conventional tillage treatment. Plots under no-till and chisel treatments in 0–10 cm depth, had 7–13%, 34–35% and 9–15% higher non-labile fraction (Cfrac4), very-labile fraction (Cfrac1) and total organic carbon (TOC), respectively compared to that of conventional ones. Also, no-till system had higher passive carbon pool and carbon management index than conventional system. In addition, the conservative tillage, reduced soil bulk density compared with conventional tillage in the surface layer. The stability of slow-wetting and room storage aggregates from conservative tillage were significantly higher (p < 0.05) than conventional tillage. Overall, stability of soil aggregates is improved under conservative tillage. Tillage system, crop rotation and residues, increased soil available nutrients N, P and K in the 0–10 cm depth, with the highest values in no-tillage system. Therefore, conservation tillage could be recommended as a tillage practices that improve fertility soil characteristics and production sustainability.

A Life Cycle Assessment of Biomass Production from Energy Crops in Crop Rotation Using Different Tillage System

A three-year experiment was carried out in Central Greece to assess the use of different tillage practices (Conventional, Reduced, and No tillage) for seedbed preparation, in a double cropping per year rotation of irrigated and rainfed energy crops for biomass production for first- and second-generation biofuel production. A life cycle assessment (LCA) study was performed for the first year of crop rotation to evaluate the environmental impact of using different tillage practices, identifying the processes with greater influence on the overall environmental burden (hotspots) and demonstrating the potential environmental benefits from the land management change. LCA results revealed that fertilizer application and diesel fuel consumption, as well as their production stages, were the hot-spot processes for each treatment. In the present study, different tillage treatments compared using mass- and area-based functional unit (FU), revealing that reduced tillage, using strip tillage for spring crop and disc harrow for winter crops, and no tillage treatment had the best environmental performance, respectively. Comparison between the prevailing in the area monoculture cotton crop with the proposed double energy crop rotation adopting conservation tillage practices, using mass and energy value FU, showed that cotton crop had higher environmental impact.

Soil Phosphorus Fractions After Long-Term Fertilizer Placement in Different Kansas Soils

Phosphorus (P) fertilizer placement can affect the long-term dynamics and forms of P, and the overall soil P pools. These changes can vary by soil type, and affect P uptake and use efficiency by crops. The objective of this study was to evaluate the changes in the labile P fractions in three Kansas soil types under P fertilizer placements (broadcast versus deep band) after ten years of crop rotation. Three field studies were conducted at Scandia, Ottawa, and Manhattan. Three treatments were evaluated: 1) a control with no P fertilizer application and two fertilizer treatments (80 lb P2O5/a); 2) surface broadcast; and 3) deep band at approximately 4–6 in. depth. All treatments received strip-tillage. After ten years, soil samples were collected from the row, and between the row at two sampling depths (0–3 and 3–6 inches) and soil P pools (inorganic and organic P labile) were measured. Significant changes in soil labile P pools for treatments compared to control were observed due to the long-term effect of P fertilizer placement. The broadcast P fertilizer placement increased the total labile (PtLP) and inorganic labile P (PiLP) in the soil surface (0–3 in.) and deep band in the subsoil (3–6 in.) at all sites studied. However, the highest amount of organic labile P (PoLP) was observed for the control broadcast treatments in the subsoil (3–6 in.) at the Scandia site. The total labile P was affected by maximum P adsorption capacity (MPAC) and P fertilizer placement.

Crop rotation reduces the density of volunteer plants in processing tomato fields and the inoculum of bacterial spot

Volunteer plants are a problem for agriculture because they compete for nutrients and can be the inoculum sources of many diseases. We investigated the contribution of crop rotation in the control of volunteer plants in commercial fields of processing tomato in the Central-West Region of Brazil and the occurrence of tomato diseases in these plants. The number of volunteer plants per hectare was estimated and compared between commercial fields with 1 and 2 years of crop rotation or without crop rotation. The rotation of processing tomato crops with soybean, maize, sweet corn and bean crops was able to significantly reduce numbers of volunteer plants. Consecutive tomato cultivation promoted a higher number of volunteer plants for the next crop. Samples of volunteer plants symptomatic for bacterial spot were collected for identification of the causal agent. Thirty-nine isolates were obtained from two areas. These isolates were pathogenic when inoculated in tomato plants. All isolates were identified as Xanthomonas perforans by specifics primers. We concluded that crop rotation is an efficient practice to reduce volunteer plants in processing tomato crops. This method can reduce the inoculum sources of disease transmitted by seeds, like bacterial spot.

How measures of agricultural landscape patterns are affected by crop rotation dynamics

Landscape patterns have been measured as a fundamental part of landscape ecology, especially with increasing computational power and availability of landcover data. Among the challenges associated with landscape measurement is identifying the appropriate scale of application, both temporal and spatial. Measurement of landscape patterns in highly-dynamic landscapes is especially challenged by temporal scale selection. This short communication focuses on how landscape pattern measurements vary in response to normal variability in a highly-dynamic landscape For a small agricultural landscape with known crop rotation dynamism sequences, a simulation model provided 30 years of crop rotations. These 30 different landscapes were measured with landscape pattern measurements and the variability of the measurements was assessed. Almost half of the measurement values were outliers, and 12 of the 30 years had at least one outlier landscape pattern measurement value, even though the basis of landscape change was a normative agricultural practice. For a consistent but dynamic landscape, some landscape measurements or simulation years had high variability, demonstrating that inferences from highly-dynamic landscapes need to be based on fine-resolution time steps. The application of landscape pattern measurements continues to be a common method in landscape ecology, and temporal dimensions are key to detecting change and what might be causing or responding to that change. The temporal resolution of change implies that highly-dynamic landscapes require more-frequent sampling, and that comparisons for agricultural landscapes over long time periods requires more than a single temporal endpoint.

Maintenance of N cycling gene communities with crop-livestock integration management in tropical agriculture systems

Five different agricultural management systems and a forest fragment at two farms were investigated for effects on soil bacterial indicators. This study was conducted in southern Mato Grosso do Sul, Brazil, in January 2014, at two farms that incorporated integrated crop-livestock systems in Hapludox soil. Impacts of management were assessed through evaluation of functional bacterial communities using quantitative PCR (qPCR) of nitrogen cycling genes (amoA, nirK, and nosZ), PCR-DGGE of the nirK community composition, and by investigating relationships of the nirK community with soil properties. The nirK gene community showed that reference forest soil maintained relatively large nirK, nosZ, but small amoA gene abundances and large range weighted nirK richness (Rr). The introduction of pasture into crop-livestock integration management (inclusion of the second and third year of grazing within a crop-livestock integration system, CL-2 and CL-3, respectively) or the field in its first year of crop rotation after grazing pasture (CL-b) increased nosZ and amoA abundance. Three years of grazing pasture in crop-livestock integration (CL-a) increased nirK abundance, while multiple years of crop rotation in crop-livestock integration management systems increased soil OM and promoted a richer nirK community composition. The nirK community Rr that was not significantly different from the forest was observed in the second or third year of crop rotation after grazing (CL-c or CL-d, respectively) and (CL-3). In contrast, fields in pasture (CL-a, continuous pasture (CP)) and the first year of crop rotation after pasture (CL-b) had reduced Rr and functional organization curves, indicating communities less resilient to future stress. Management systems under integrated crop-livestock farming in tropical soil maintained a relatively diverse N cycling bacterial community, possibly promoting soil quality and N cycling processes.