3-year Rotation Research Articles

The Dynamics of Secondary Mangrove Forests in Bintuni Bay, West Papua after Harvested on the First 30-Year Rotation Cycle

Mangrove forests in Bintuni Bay, West Papua, Indonesia, have been managed for timber extraction since 1988 to produce wood chips using a 30-year rotation cycle. The first rotation cycle was completed, resulting in secondary mangrove forests with various stand ages (1–30 years). A large-scale forest inventory was conducted for all harvested blocks to recognize actual standing stock for the 2021–2030 management plan. A total of 434 quadrat plots (20 m x 20 m) covering 17.36 ha each were used to observe forest standing stock. The results present the dynamics of secondary mangrove forests after the initial rotation cycle. At the end of the first cycle (30-year-old stand), secondary mangrove forests provided a volume of 290.12 m3 ha-1 and potential extractable biomass of 203.03 ton ha-1 with mean diameter, basal area, and stem density of 16.91 cm, 29.18 m2 ha-1, and 1,370 stem ha-1, respectively. Annual increment of volume, biomass, and diameter were estimated to be 9.67 m3 ha-1 year-1, 6.77 ton ha-1 year-1, and 0.56 cm year-1, consecutively. The dynamics of secondary mangrove forests could provide significant information in the context of the management plan and implementation of the silviculture system to ensure the sustainability of utilization in managed mangrove forests. Keywords: Forest regeneration, Silviculture, Standing stock, Sustainable management, Timber utilization

Effects of Crop Residues and Tillage Operations on Soil Quality Indices

Tillage and plant residues influence soil attributes and, consequently, soil quality. Therefore, suitable management and maintaining the stability of soil structure is important. This study was performed to evaluate the effects of tillage systems on soil quality during a 4-year crop rotation (wheat, canola, wheat and tomato) at the Agricultural Research Center of Khorasan Razavi province (Iran) from 2011 to 2015. The study was conducted as a randomized complete block design in a factorial arrangement with 3 replications. For this purpose, conventional tillage (CT), minimum tillage (MT) and no-tillage (NT) systems together with three rates of plant residues (0, 1,500, and 3,000 kg ha-1) were applied annually after harvesting. Soil quality was determined by using the integrated quality index (IQI) and Nemoro quality index (NQI) based on total data set (TDS) and minimum data set (MDS). In total, 23 physical, chemical, and biological soil characteristics were considered as TDS and 7 out of these were selected as MDS for use in the principal component analysis (PCA). Soil quality in different tillage treatments was determined and the most appropriate indices and effective characteristics for soil quality assessment were selected. Correlation coefficients between IQITDS and IQIMDS (r = 0.69) and between NQITDS and NQIMDS (r = 0.76) showed that NQI was a better indicator for assessing soil quality. The NQITDS provided a more accurate and comprehensive assessment of soil quality. However, using MDS reduced the cost and time with proper precision. Soil quality in MT and NT treatments was more desirable than the CT system, and the addition of plant residues improved the soil quality. According to the results of NQITDS, IQITDS, and IQIMDS, soil quality in the NT system with 3,000 kg ha-1 of plant residues and the MT system with 1,500 and 3,000 kg ha-1 of plant residues were more favorable than other soil tillage treatments. Soil characteristics that decreased soil quality in the conventional tillage were soil structure, macro and micronutrients, while in conservation tillage it was micronutrients, especially Zn.

Integrated highland wildfire, smoke, and haze management in the Upper Indochina region

Fire has long been used in Southeast Asia for the purposes of cooking, protection, and warmth. However, climate change and economic pressure have modified the life of locals, including fire practices in daily life and other fire uses. The land use of forest cover in highland area (mostly deciduous forest) has shifted to cultivation, with the application of slash-and-burn techniques. This results in frequent unplanned fires causing pollution in the form of smoke and haze. A zero-burn policy has been implemented to tackle this problem but such a policy may not be appropriate as people still need fire as a basic tool for agriculture land preparation. Moreover, the deciduous forest is a fire-dependent ecosystem to maintain its ecosystem. Frequent burning by local people or excessive government intervention in preventing fires can impact this ecosystem. In the highlands, shifting cultivation has gradually been replaced by rotational agricultural practice with a cycle of 2 to 5 years. However, the fuel load for a 2-year rotation period is only 0.25 tha-1 higher than that of a mixed deciduous forest. New fire risk maps classified according to forest types were produced for Thailand, Lao PDR, and Myanmar. We report that the mixing layer (ML) height in Chiang Mai Province was, on average, 500 m during March, with common occurrence of subsidence inversion resulting in further lowering of air quality during this month. A participatory process to develop a Community Based Fire Management (CBFiM) was undertaken and it was observed that a successful implementation would need a community with a strong leadership.

Cropping system diversification does not always beget weed diversity

Cropping system (CS) diversification appears as a promising solution to increase CS sustainability. However, weed community response to different options of CS diversification remains poorly documented. Moreover, these effects are expected to be more pronounced in experimental than commercial farms because experimental farms explore more diverse combinations of farming practices. We hypothesized that (i) CS diversification would increase weed diversity at multiple spatio-temporal scales but that (ii) different options of CS diversification would select different weed communities and that (iii) responses could differ between experimental and commercial farms. Hence, weed density per species was measured over a 6-year time period in a CS experiment and in a farmers’ network (both resorting to diverse CSs that were numerically summarized to allow their comparison, i.e. different positions along gradients of tillage intensity, herbicide use, crop rotation length etc.). Weed density measures were used to compute weed diversity indices (taxonomic and functional, at annual and plurennial scales) and community weighted means on key response traits for each CS. All experimented alternative CSs (diversified crop sequences with coherent but different combinations of weed management tools) showed that diverse combinations of agronomic tools are available to increase weed diversity, as highlighted by a 3 and 2-fold increase in species richness at the annual and plurennial scales, respectively. In contrast, only one farmer CS (3-year rotation, low tillage intensity, intermediate herbicide reliance) showed significantly higher levels of weed diversity, possibly because the reduced tillage intensity was not compensated by other agronomic levers (e.g. increase of herbicide use and/or crop rotation diversity). Such outcomes were attributed to (i) reduced CS complexity in commercial compared to experimental farms and (ii) high herbicide reliance in commercial farms, irrespectively of CS complexity. Across both experimental and commercial farms, tillage, weed management and crop type appeared as the main factors structuring weed communities. Systems with reduced tillage were associated with a higher percentage of grasses and perennials. Systems with spring/summer crops and/or mechanical weeding were associated with a higher proportion of spring/summer and perennial species. These results suggest that solutions are readily available for farmers to implement sustainable weed management, but supports are required to address the factors hindering the adoption of these experimented CS in commercial conditions.

Introducing cover crops as fallow replacement in the Northern Great Plains: II. Impact on following wheat crops

AbstractThe introduction of cover crops as fallow replacement in the traditional cereal-based cropping system of the Northern Great Plains has the potential to decrease soil erosion, increase water infiltration, reduce weed pressure and improve soil health. However, there are concerns this might come at the cost of reduced production in the subsequent wheat crop due to soil water use by the cover crops. To determine this risk, a phased 2-year rotation of 15 different cover crop mixtures and winter wheat/spring wheat was established at the Northern Agricultural Research Center near Havre, MT from 2012 to 2020, or four rotation cycles. Controls included fallow–wheat and barley–wheat sequences. Cover crops and barley were terminated early July by haying, grazing or herbicide application. Yields were significantly decreased in wheat following cover crops in 3 out of 8 years, up to maximum of 1.4 t ha−1 (or 60%) for winter wheat following cool-season cover crop mixtures. However, cover crops also unexpectedly increased following wheat yields in 2018, possibly due in part to residual fertilizer. Within cool-, mid- and warm-season cover crop groups, individual mixtures did not show significant differences impact on following grain yields. Similarly, cover crop termination methods had no impact on spring or winter wheat grain yields in any of the 8 years considered. Wheat grain protein concentration was not affected by cover crop mixtures or termination treatments but was decreased in winter wheat following barley. Differences in soil water content across cover crop groups were only evident at the beginning of the third cycle in one field, but important reductions were observed below 15 cm in the last rotation cycle. In-season rainfall explained 43 and 13% of the variability in winter and spring wheat yields, respectively, compared to 2 and 1% for the previous year cover crop biomass. Further economic analyses are required to determine if the integration of livestock is necessary to mitigate the risks associated with the introduction of cover crops in replacement of fallow in the Northern Great Plains.

Эффективность удобрения под подсолнечник на чернозёме типичном Тамбовской области

Currently, sunflower is the main oil crop in the Tambov region. The most important task of modern agricultural production is the use of technologies that increase the yield and quality of field crops. Data on seed and oil yield of sunflower are very important when choosing different types of mineral fertilizers. In this regard, the purpose of our research was to study the effect of various doses, methods and terms of application of macro- and microfertilizers on yield, crop quality and oil yield of sunflower in a link of the 6-year crop rotation: fallow – winter wheat – corn (for grain) – barley – sunflower – spring wheat. The research was conducted at the Tambov Research Institute of Agriculture – a branch of the I.V. Michurin Federal Research Center, which is located in the Tambov region. On typical black soil, application of both traditional mineral fertilizers (N16P16K16) for plowing, and liquid mineral fertilizers (Megamix) during pre-sowing treatment and for plants treatment during vegetative period contributes to obtaining an additional seed and oil yields. For 2014–2020, the highest seed and oil yields were obtained in variant (5) with N30P30K30 for plowing + seed treatment with Megamix (2.0 l/t) and amounted to 2.84 t/ha and 1324 kg/ha, respectively. The fat content varied depending on the variant of the experiment. The maximum indicator of 53.6% was in the variant with the application of N30P30K30. But due to the lower seed yield, the oil yield amounted to 1.21 t/ha. All variants for seed and oil yields were superior to the control one (without fertilizers).

Productivity, light interception and radiation use efficiency of organic and conventional arable cropping systems

How the productivity of crops in organic arable farming may be sustainably increased remains a key issue. We combined measurements of crop yield, total aboveground biomass (AGB) and light interception over a 4-year crop rotation cycle from 2015 to 2018 in a long-term experiment in Denmark with arable organic and conventional cropping systems. These cropping systems comprise one conventional (CGL) and two organic (OGL and OGC) crop rotations, where CGL and OGL had three spring cereal and one grain legume crop (faba bean) in the rotation, and the faba bean was in OGC replaced with grass-clover. All crop rotations were grown with and without the use of cover crops, and the organic systems were grown with and without the manure application. The light interception was calculated from measurements of spectral reflectance, and this allowed the AGB to be decomposed into accumulated intercepted PAR (AIPAR) and radiation use efficiency (RUE).The conventional cropping system (CGL) had significantly greater AGB, AIPAR and RUE compared with the corresponding organic, grain legume-based system (OGL). AIPAR of the organic grass-clover-based cropping system (OGC) was greater than CGL, although the contrary conclusion was found in AGB and RUE. Across crops, RUE was greatest for cereals and smallest for faba bean and grass-clover. AIPAR was consistently greatest for grass-clover, and both grass-clover and faba bean had smaller variability in AIPAR between years and treatments than the cereal crops. Cover crops significantly increased AGB and AIPAR in the organic cropping systems but not in CGL. RUE was not significantly affected by the inclusion of cover crops. The use of manure in the organic systems increased AGB, AIPAR and RUE. The results show that AIPAR can be higher in organic cropping systems compared with conventional cropping systems, but this is not translated into a greater yield of cereal crops. There is, therefore, a need for novel approaches to management and the use of biomass in organic cropping systems for increasing yields for feed and food, and which sustains soil fertility.

Temporal and scalar variations affect resource use of northern bobwhite broods.

Disparate resource use originating from phenology of biotic resources, abiotic conditions, and life cycles of exploiting organisms underscores the importance of research across time and space to guide management practices. Our goal was to evaluate resource use of northern bobwhite (Colinus virginianus; bobwhite) at two spatial scales and across three age classes, from hatching through a period of the postjuvenile molt. Our study was conducted at Tall Timbers Research Station, Tallahassee, FL, USA—situated in a landscape subjected to small scale (<20 ha) prescribed fires on a 2‐year fire rotation. We predicted prescribed fire, disking, and supplemental feeding would dictate resource use, but effects would depend on time since fire, brood age, and time of day. We predicted vegetation and temperature would govern roost use by broods, but these effects would also depend on age. We radio‐tracked 62 broods 21–35 times / week during May–October 2018 and 2019. Broods were less likely to use areas with large proportions of hardwood drains but favored sites with greater proportions of burned uplands, regardless of the time of day. Broods were less likely to use areas at greater distances from supplemental feed; this relationship had no interaction with age but was stronger later in the nesting season (>July 15). Broods were more likely to use areas with greater proportions of fallow fields during the day than for roosting. Broods used roosts with more woody cover and visual obscurity than at available sites. Roosts consisted of less grass and bare ground. However, these effects interacted with age; broods used sparser cover at older ages. Neonate broods were more likely to use cooler roosts with greater thermal stability, but this effect was reversed for juveniles. Broods may alter resource use with changes in vulnerabilities to threats such as thermal risks and predation.

The Value of Hybrid Aspen Coppice Investment under Different Discount Rate, Price and Management Scenarios: A Case Study of Estonia

Hybrid aspen is one of the most promising tree species for short-rotation forestry in Northern Europe. After the clearcutting of hybrid aspen plantation, the next generation arises from root and stump sprouts. The economic feasibility of different management strategies of hybrid aspen coppice stands has not yet been comprehensively evaluated in Northern Europe. We compared the land expectation values (LEVs) of hybrid aspen coppice stands managed according to four scenarios: three early thinning methods (corridor, cross-corridor and single-tree) followed by conventional management and intensive bioenergy production (repeated harvests in 5-year rotations) over a 25-year period in hemiboreal Estonia. We considered the historic price volatility of aspen wood assortments under various discount rates (1–20%). We found that the 25-year rotation with different early thinning methods was more profitable than short bioenergy cycles in the case of low discount rates (&lt;5%). The LEV of short coppice cycles for only bioenergy production became more profitable in comparison with those by thinning methods, when higher discount rates (&gt;10%) were applied. Hybrid aspen coppice stands can be managed profitably, but more risks are taken when the management strategy focuses only on bioenergy production.

Design and multicriteria assessment of low-input cropping systems based on plant diversification in southwestern France

Lengthening and diversifying crop rotations is an efficient strategy to reduce the use of fertilizers and pesticides, thereby improving the sustainability of cropping systems. To test this assumption, six innovative cropping system prototypes were designed, each introducing one or more agroecological practices, as alternatives to the 2-year sunflower (Helianthus annuus L.)–durum wheat (Triticum turgidum L. subsp. durum) rotation widespread in southwestern France. Two 3-year rotations were implemented at INRAE, Toulouse, from 2011 to 2016. The six prototypes were composed of two low-input cropping systems (with/without cover crops) and four very low-input cropping systems (including cultivar or species mixtures, each with/without cover crops). As compared to the sunflower–wheat rotation, the prototypes aimed at reducing the use of N fertilizers by 25% (low-input) and 50% (very low-input) and pesticides by 50%. A set of agronomic, environmental, technical, and socio-economic indicators was calculated to assess the different components of sustainability. The introduction of agroecological principles resulted in a clear reduction of the use of synthetic inputs as compared to the sunflower–wheat rotation. The treatment frequency index was decreased by 56, 18 and 39% for the low-input cropping systems, very low-input cropping systems with cultivar mixtures, and very low-input cropping systems with species mixtures, respectively. However, the profitability decreased with the diversification of cropping systems as the semi-net margin decreased for the three previous cropping systems (745, 696, and 438 €·ha−1, respectively, vs. 963 €·ha−1 for the sunflower-wheat rotation). Despite the costs of inputs, the short rotation remained the most profitable. Agroecological practices succeeded in reducing the dependence of cropping systems on synthetic inputs, but their implementation needs to be improved to achieve better economic performance, using both scientific knowledge and know-how of innovative farmers.

Rotation regimes lead to significant differences in soil macrofaunal biodiversity and trophic structure with the changed soil properties in a rice-based double cropping system

Crop production has negative effect on the biodiversity in farmlands because of less crop varieties and intensive soil disturbance. Macrofauna are important components of the belowground biodiversity, and contribute to the soil ecosystem functions and soil processes. The response of soil macrofauna to cropping pattern is crucial for understanding the soil ecological dynamics and biodiversity conservation. Herein, we established an experiment of rice (Oryza sativa L.)-based double cropping system in Jiangsu Province, China since 2016 to evaluate the effects of rotation regimes on soil properties and soil macrofauna communities. The rice-based double cropping system included rice–wheat (Triticum aestivum L.), rice-oilseed rape (Brassica campestris L.), rice-tiny vetch (Vicia hirsuta L.), rice-broad bean (Vicia faba L.), and rice-fallow. After 3-year rotations, soil macrofaunal biodiversity and trophic structure varied significantly with soil properties. The higher biodiversity indices were found in the tiny vetch (used as green manure in situ) and fallow fields. In addition, soil organic carbon (SOC), the main factor for shaping the soil environment and regulating the soil macrofaunal communities, was improved. While soil water content and pH were selected to predict each trophic richness and density in most of the optimal regression models, changes in soil macrofaunal communities should also be considered as comprehensive responses to the soil environments (food resources, microhabitats etc.) co-varying rotation regimes. Crop rotation with lower intensity of land use increased the complexity of soil macrofaunal trophic structure. Green manure fields or fallow after rice plantation promoted soil macrofaunal biodiversity in the rice-based cropping system.

N2O emissions in Acacia mangium stands with different ages, in Sumatra, Indonesia

We compared nitrous oxide (N2O) emissions in different-aged (1, 3, and 5 years) Acacia mangium plantations and secondary forests for two and a half years at three areas in Sumatra, Indonesia. N2O emission was high from November to March (rainy season) and low from May to November (relatively drier season). In the first year, the average ± standard deviation of annual N2O emissions in 1-year-old sites was 8.92 ± 2.29 kg ha−1 of N, which was larger than those in 3-year-old (2.58 ± 2.28 kg ha−1 of N) and 5-year-old (2.16 ± 1.12 kg ha−1 of N) sites and secondary forests (1.38 ± 0.45 kg ha−1 of N) (p < 0.001). However, there is no significant difference in N2O flux among treatments after the second year. Although nitrogen mineralization and nitrification potential did not differ among tree ages, inorganic nitrogen and NH4/NO3 ratio in 1-year-old acacia site in the first year were significantly different from those in the other aged forests and secondary forests. Results of linear mixed model suggest that water-filled pore space and nitrogen availability are key factors for N2O emission in these sites. N2O emission within 1 year after planting contributed to 41% of total emission during the 7-year rotation period. Therefore, reduction in N2O emission within 1 year after planting is important for the total emission from acacia plantation.

Effects of Crop Rotation on Spring Wheat Yield and Pest Occurrence in Different Tillage Systems: A Multi-Year Experiment in Finnish Growing Conditions

Crop rotation and soil tillage are among key factors impacting cropping system productivity, pest management and soil health. To assess their role in northern cropping systems, we quantified the effects of crop rotation on spring wheat yield in different tillage systems based on a long-term (2005–2017) field experiment in southwestern Finland. In addition, effects of crop rotation on weeds, plant pathogens, and pest insects were assessed. Three types of crop rotation were compared: monoculture (spring wheat), 2-year rotation (spring wheat—turnip rape—spring wheat—barley) and 4-year rotation (spring wheat—turnip rape—barley—pea) under no-tillage and plowing. A diversified crop rotation improved spring wheat yield by up to 30% in no-tillage and by 13% under plowing compared with monoculture. Overall, the yield quantity and quality differences between crop rotations were higher in no-tillage plots than in plowed plots. The occurrence of weed species in spring wheat before herbicide control was highest in the four-year crop rotation and lowest in the wheat monoculture. For plant diseases, wheat leaf blotch disease severity, mainly caused by Pyrenophora tritici-repentis, was lowest in the most diverse crop rotation. On average, wheat leaf blotch disease severity was 20% less when wheat was grown every fourth year compared with wheat monoculture. The effect of crop rotation on stem and root diseases became apparent after 6 years of rotation and the disease index was lowest in the most diverse crop rotation. Neither rotation nor tillage affected the control need of wheat midge (Sitodiplosis mosellana). Based on our results, diverse crop rotations including cereals, oilseed crops, and legumes increase yield and reduce plant disease severity of spring wheat in Finland, with the magnitude being larger in no-tillage systems.

Growth and profitability of smallholder sengon and teak plantations in the Pati district, Indonesia

Despite the ambitious target to establish 12.7 million ha of social forestry across Indonesia and various government support for smallholder private forests, implementation has been slow and financial returns for smallholders from timber production have been variable. For most smallholders, any motivation to plant trees competes with their interest in planting short term food or cash crops to support their family's livelihood. Moreover, lack of market knowledge and monetary need often sees smallholders sell their trees at below market prices, rather than at the optimum time for financial returns. Also, a limited understanding of silvicultural options to improve log quality further undermines the financial returns from timber production for smallholders. There are few studies from Indonesia that provide sufficient detail to be able to replicate the financial analysis and benchmark the results against key input variables (e.g., unit costs of production, timber yields by product and log size class, discount rate). Another deficiency is the lack of empirical data on the growth performance of existing smallholder plantations in Indonesia. This article reports on research to fill these knowledge gaps by using inventory data from smallholder plantations in Pati (Central Java) together with other data to develop silvicultural systems that were used to assess the profitability for smallholders of growing sengon (Paraserianthes falcataria) and teak (Tectona grandis) for timber. The results indicated that growing sengon on a 6-year rotation was profitable with an estimated net present value (NPV) of USD 1015 ha−1 (Rp 14,218,000 ha−1) at a real discount rate of 8%, with an internal rate of return (IRR) of 20%. Growing teak on a 20-year rotation was also profitable with an NPV of USD 2815 ha−1 at a real discount rate of 8%, and an IRR of 15%. Although the NPV for teak was nearly three times that for sengon, in the long term (i.e., over perpetual rotations), the returns from sengon and teak were closer. Our results support the view that the best opportunity for enhancing smallholder returns from forestry lies in improving the common approach to silviculture, particularly the lack of effective pruning and thinning, to realise the financial potential of timber production.

Increased hydraulic constraints in Eucalyptus plantations fertilized with potassium.

Fertilization is commonly used to increase growth in forest plantations, but it may also affect tree water relations and responses to drought. Here, we measured changes in biomass, transpiration, sapwood-to-leaf area ratio (As :Al ) and sap flow driving force (ΔΨ) during the 6-year rotation of tropical plantations of Eucalyptus grandis under controlled conditions for throughfall and potassium (K) fertilization. K fertilization increased final tree height by 8m. Throughfall exclusion scarcely affected tree functioning because of deep soil water uptake. Tree growth increased in K-supplied plots and remained stable in K-depleted plots as tree height increased, while growth per unit leaf area increased in all plots. Stand transpiration and hydraulic conductance standardized per leaf area increased with height in K-depleted plots, but remained stable or decreased in K-supplied plots. Greater Al in K-supplied plots increased the hydraulic constraints on water use. This involved a direct mechanism through halved As :Al in K-supplied plots relative to K-depleted plots, and an indirect mechanism through deteriorated water status in K-supplied plots, which prevented the increase in ΔΨ with tree height. K fertilization in tropical plantations reduces the hydraulic compensation to growth, which could increase the risk of drought-induced dieback under climate change.

Crop response to P fertilizer omission under a changing climate - Experimental and modeling results over 115 years of a long-term fertilizer experiment

• The omission of P had a rather small effect on winter cereal yields. • Sugar beet, clover and potato yields were most affected by P deficiency. • Raising air temperature reduces yield loss caused by phosphorus limitation. Phosphorus (P) is an essential plant nutrient. However, our understanding of the complex interactions between soil P availability, environment, management and crop growth is still limited. We used unique historic and recent soil and crop data spanning more than a century combined with a process-based crop model to analyze the impact of P fertilizer omission and P fertilization on the biomass production of five crops. The long-term field experiment at Dikopshof, Germany, was established in 1904 with a 5-year crop rotation of sugar beet, winter wheat, winter rye, clover and oat/potato (potato replaced oat in 1953) on a fertile Luvisol. Averaged over the period from 1906 to 2018, the yield loss due to P omission was low for winter wheat and winter rye (7–8 %). In contrast, yield losses for sugar beet, clover and potato were relatively high (15–24 %). The yield loss from P fertilizer omission in comparison to the reference treatment (rotation mean excluding oat/potato) increased until the middle of the last century from 7% to 18 %, but subsequently decreased to 13 %. Trend and correlation analyses suggest that this decrease was related to an increase in air temperatures in especial during spring and a lower yield loss under P omission. Crop model simulations showed decreasing topsoil organic carbon concentrations after the 1930ies as manure was discontinued in 1942 but also due to increasing air temperatures. The increase in plant-available topsoil P concentrations during the last decades was one of the main factors offsetting yield losses despite P fertilizer omission. Our study suggests that climate change and, in particular, a marked increase in temperature since the middle of the last century most likely influenced soil P dynamics with a significant impact on crop production.

Yield, nitrogen, and water use benefits of diversifying crop rotations with specialty oilseeds

Decreased agricultural diversity from extensive use of the corn (Zea mays L.)- soybean (Glycine max (L.) Merr.) rotation and occasional inclusion of spring wheat (Triticum aestivum L.), has threatened cropping system sustainability. Using specialty oilseeds crops to extend the corn-soybean rotation might improve yields and promote sustainability. We tested whether corn, soybean, and wheat yields would be improved in a rotation following oilseed crops versus corn or soybean. In Phase 1, replicated blocks of nine different flowering oilseeds and two traditional grain crops (corn and soybean) were grown. In phase 2, corn, soybean, and wheat were planted in replicated blocks perpendicular to the previous year crops. This 2-year rotation was repeated for three site-years, two in Morris, MN and one in Brookings, SD. Soil water balance was evaluated during Phase 1 of the rotation to determine seasonal water use. Potential N mineralization was measured in the spring prior to planting in a subset of phase 1 treatments (spring canola, cuphea, corn, and soybean). Linear mixed models were used to analyze Phase 2 corn, soybean and wheat yield responses to previous crop. N dynamics and water use responses to phase 1 crops were also analyzed with mixed models. Corn yield was higher with any previous crop other than corn. Soybean and wheat yields did not significantly respond to previous crop. Yield patterns were partially explained by N mineralization potential and previous crop water use. Spring canola treatments provided higher potential net nitrification compared to corn. Canola, camelina, borage, and crambe had lower seasonal water use than both corn and soybean in at least one site-year. This short-term study indicated that corn and soybean yields following specialty oilseed crops had similar yields to a traditional corn-soybean rotation. Further, oilseed crops in rotation provided additional environmental benefits.

Type of pulse crop included in a 2-year rotation with wheat affects total N2O loss and intensity

Type of pulse crop included in a 2-year rotation with wheat affects total N2O loss and intensity

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

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

Leptosphaeria maculans Isolates Reveal Their Allele Frequency in Western Canada.

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