Effects Of Crop Management Practices Research Articles

Assessing the joint effects of landscape, farm features and crop management practices on berry damage in coffee plantations

Coffee berry borer (CBB) (Hypothenemus hampei; Coleoptera: Curculionidae: Scolytinae) is a major insect pest affecting coffee cultivation that causes large economic losses worldwide. Characteristics related to its life cycle makes it very difficult to control. Usually, CBB control measures are carried out at plot scale, with almost no actions taken at wider landscape scales. It is unclear how plot level control strategies and landscape factors act alone or in combination to influence CBB infestation levels. We evaluated the joint effects of crop management at the plot level, of farm features, and of landscape structure at different spatial scales on CBB infestation in 50 Costa Rican coffee farms. On five plants in each farm, we estimated the maximum number of infested berries during the fruiting period. We measured three separate groups of variables related to plot management practices, farm features and landscape structure. To assess their single and joint contributions, their relative importance and the effects of these variables on the number of infested berries we used the variance partitioning approach of the RandomForest algorithm. When evaluating the groups of factors separately, we found that crop management explained 35% of the variability of number of infested berries, farm features 42% and landscape structure 27%. The joint contribution of all three groups of variables explained 48% of variability of the number of infested berries. However, when we assessed the single contributions of each set of variables, i.e., when controlling the other two set of variables, we found that farm features explained 17% of the variance of the number of infested berries, landscape structure 6% and crop management practices only 3%. The larger amount of the variance explained by the joint effect of crop management practices, farm features, and landscape structure suggests that to develop a pest management strategy at a local scale it is important to consider the effect of both local and landscape factors affecting pest abundance. The integrated CBB management plan should consider influences at multiple spatial scales and a coordinated action among farmers that share the same landscape would be beneficial.

The Impact of Conservation Agriculture Practice and Socio-Economic Factors on Yam Production (Dioscorea alata and Dioscorea rotundata) in Kalagoé (Lobaye, Central African Republic)

Few studies have been carried out on Yam (Dioscorea alata and Dioscorea rotundata) in relation with the conservation agriculture in CAR. Yam is cultivated in limited quantities despite its role in improving food security. In order to increase Yam production in the smallholder farms in CAR, the potential effect of crop management practices like nutrient application, mulching and minimum tillage on Yam crop yield and household financial returns, needs to be understood. A questionnaire was prepared and used as a tool for the collection of information from 100 producers of Yam without distinction of ages and sexes. In order to determinate the agronomical performance of Yam, two plots were explored. The first plot with 625m² (12.5m ×50m), known as the improved plot, is a plot on which all conservation agriculture practices were applied. The second plot, known as the traditional plot, is one on which traditional farming techniques were applied. The results of the survey show that 32% of the farmers are in favor for CA practice nevertheless 68% are not favor, which shows that a large proportion of farmers in Kalangoé are not aware of the benefits of this technique. The most widely cultivated variety is D. rotundata, because of its taste qualities. Some producers also grow both varieties at the same time. Some producers (28%) clear their plots by cutting down all the trees to leave the field bare, while a large number (72%) practice partial cutting by removing the shrubs to keep the large trees in order to protect the forest. A large number of producers (62%) also burn their plots for various reasons, including freeing up space and making it easier to move around the field because the plant debris from clearing prevents them from working properly. A small proportion of producers (26%) practice ploughing against 74% who do not practice this technique. The conservation agriculture practice applied to Yam gave interesting agronomic performances (growth and production parameters) than the farmers practices.

No Tillage Improved Soil Pore Space Indices under Cover Crop and Crop Rotation

Assessment of the effects of crop management practices on soil physical properties is largely limited to soil moisture content, air content or bulk density, which can take considerable time to change. However, soil pore space indices evolve rapidly and could quickly detect changes in soil properties resulting from crop management practices, but they are not often measured. The objective of this study was to investigate how soil pore space indices—relative gas diffusion coefficient (Ds/Do) and pore tortuosity factor (τ)—are affected by tillage system (TL), cover crop (CC) and crop rotation (CR). A study was conducted on silt loam soil at Freeman farm, Lincoln University of Missouri during the 2011 to 2013 growing seasons. The experiment design was a randomized complete block with two tillage systems (no tillage or no-till vs conventional tillage), two cover crops (no rye vs cereal rye (Secale cereale L.)) and four crop rotations (continuous corn (Zea mays L.), continuous soybean (Glycine max L.), corn–soybean and soybean–corn successions). All the treatments were replicated three times for a total of 48 experimental units. Soils were collected from two sampling depths (SD), 0–10 and 10–20 cm, in each treatment and soil physical properties, including bulk density (BD), air-filled porosity (AFP, fa) and total pore space (TPS, Φ), were calculated. Gas diffusivity models following AFP and/or TPS were used to predict Ds/Do and τ values. Results showed that, overall, Ds/Do was significantly increased in no-tilled plots planted to cereal rye in 2012 (p = 0.001) and in 2013 (p = 0.05). No-tilled continuous corn, followed by continuous soybean and no-tilled soybean–corn rotations had the highest Ds/Do values, respectively. In magnitude, Ds/Do was also increased in no-till plots at the lower depth (10–20 cm). No-tilled plots planted with cereal rye significantly reduced τ in 2012 (p = 0.001) and in 2013 (p = 0.05). Finally, at the upper depth (0–10 cm), the no-tilled corn–soybean rotation and the tilled soybean–corn rotation had the lowest τ. However, at the lower depth (10–20 cm), the four crop rotations were not significantly different in their τ values. These results can be useful to quickly assess the changes in soil physical properties because of crop management practices and make necessary changes to enhance agricultural resilience.

Effect of agronomic management on rice grain quality Part I: A review of Australian practices

AbstractCrop yield dominates rice (Oryza sativa L.) industry research; however, it is grain quality that dictates the value and market acceptance of rice. Key parameters of rice grain quality include physical appearance, amenability to processing and the cooking and sensory properties. In Australia, rice farmers who do not meet defined high‐quality standards receive discounts to their payments. Consequently, even with high yields, poor grain quality can negatively impact grower returns. Despite the financial consequences, the quality of Australian grown rice is highly variable, because unfortunately, the underlying causes are poorly understood. The identification of genetic markers for specific traits largely dominates rice grain quality research, while research regarding the effect of crop management practices on grain quality is relatively sparse and generally lacks an Australian focus. Prior research that has assessed the effect of crop management practices on grain quality tends to focus primarily on milling quality and neglect the physicochemical and cooking properties. This review outlines the current state of knowledge of the role nutritional management, irrigation protocols, planting density, and the interaction with genotype and environment on rice grain quality. The review highlights the uniqueness of Australian management practices and that there is a need for future research to understand the impact of agronomic practices on rice grain quality in Australia. Understanding how each cultivar interacts with agronomic practices can help reduce the variability found within rice crops.

Effect of crop management practices on soil’s carbon pool index, lability index and carbon management index under cotton based intercropping system in Vertisol

Effect of crop management practices on soil’s carbon pool index, lability index and carbon management index under cotton based intercropping system in Vertisol was investigated during 2015-16 and 2016-17 on Research Farm, Department of Soil Science and Agriculture Chemistry, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola. The treatments comprised of control (only cotton), and cotton based intercropping systems viz. cotton + dhaincha (1:1), cotton + sunhemp (1:1), cotton + green gram (1:1), cotton + cow pea (1:1), cotton + black gram (1:1), cotton + pigeon pea (6:2) and cotton + soybean (1:1) which were executed in randomized block design with three replications. The in situ incorporation of dhaincha in cotton + dhaincha intercropping system recorded improvement in physical, chemical and biological properties. Various carbon pools and soil organic carbon stock was registered highest under cotton + dhaincha (1:1) intercropping system which helped to improve carbon lability index, carbon pool index as well as carbon management index.

Effects of breeding history and crop management on the root architecture of wheat

AimsSelection for optimal root system architecture (RSA) is important to ensure genetic gains in the sustainable production of wheat (Triticum aestivum L.). Here we examine the hypothesis that past wheat breeding has led to changes in RSA and that future breeding efforts can focus directly on RSA to improve adaptation to target environments.MethodsWe conducted field trials using diverse wheat varieties, including modern and historic UK varieties and non-UK landraces, tested under contrasting tillage regimes (non-inversion tillage versus conventional ploughing) for two trial years or different seeding rates (standard versus high rate) for one trial year. We used field excavation, washing and measurement of root crowns (‘shovelomics’) to characterise RSA traits, including: numbers of seminal, crown and nodal roots per plant, and crown root growth angle.ResultsWe found differences among genotypes for all root traits. Modern varieties generally had fewer roots per plant than historic varieties. On average, there were fewer crown roots and root angles were wider under shallow non-inversion tillage compared with conventional ploughing. Crown root numbers per plant also tended to be smaller at a high seeding rate compared with the standard. There were significant genotype-by-year, genotype-by-tillage and genotype-by-seeding-rate interactions for many root traits.ConclusionsSmaller root systems are likely to be a result of past selection that facilitated historical yield increases by reducing below-ground competition within the crop. The effects of crop management practices on RSA depend on genotype, suggesting that future breeding could select for improved RSA traits in resource-efficient farming systems.

Effect of crop canopy and herbicide application on kochia (Bassia scoparia) density and seed production

AbstractUnderstanding the effects of crop management practices on weed survival and seed production is imperative in improving long-term weed management strategies, especially for herbicide-resistant weed populations. Kochia [Bassia scoparia (L.) A.J. Scott] is an economically important weed in western North American cropping systems for many reasons, including prolific seed production and evolved resistance to numerous herbicide sites of action. Field studies were conducted in 2014 in a total of four field sites in Wyoming, Montana, and Nebraska to quantify the impact of different crop canopies and herbicide applications on B. scoparia density and seed production. Crops used in this study were spring wheat (Triticum aestivum L.), dry bean (Phaseolus vulgaris L.), sugar beet (Beta vulgaris L.), and corn (Zea mays L.). Herbicide treatments included either acetolactate synthase (ALS) inhibitors effective on non-resistant B. scoparia or a non–ALS inhibiting herbicide effective for both ALS-resistant and ALS-susceptible B. scoparia. Bassia scoparia density midseason was affected more by herbicide choice than by crop canopy, whereas B. scoparia seed production per plant was affected more by crop canopy compared with herbicide treatment. Our results suggest that crop canopy and herbicide treatments were both influential on B. scoparia seed production per unit area, which is likely a key indicator of long-term management success for this annual weed species. The lowest germinable seed production per unit area was observed in spring wheat treated with non–ALS inhibiting herbicides, and the greatest germinable seed production was observed in sugar beet treated with ALS-inhibiting herbicides. The combined effects of crop canopy and herbicide treatment can minimize B. scoparia establishment and seed production.

Impacts of selected management practices on soil quality in an irrigated arid agroecosystem

Understanding the impacts of cropping systems is crucial for agricultural sustainability. A study was conducted at New Mexico State University Agriculture Science Center at Los Lunas, New Mexico, United States, to investigate the effect of crop management practices on selected soil measurements. Four management systems on medium- to fine-textured surface soil, and two other management systems on coarse-textured surface soil were assessed. Management systems within the medium- to fine-textured soils included tall fescue (Lolium arundinaceum [Schreb.]) permanent grass fields (TFC), peach (Prunus persica [L.] Batsch) orchards with white clover (Trifolium repens L.) ground cover (PCC), alfalfa (Medicago sativa L.; ALF), and conventionally tilled land with annual crop rotations (CTC). The two systems studied in the coarse-textured soils were conventionally tilled soil with annual crop rotation (CTS) and young cottonwood tree (Populus deltoides W. Bartram) orchards (CWS). Soil samples were collected in three fields for each of the management systems at 0 to 15 and 15 to 30 cm. Twelve out of the 16 soil measurements assessed in the upper depth varied significantly with management system, while 10 out of the 16 measurements were significantly affected at the lower depth. With regard to agricultural productivity, management systems with permanent ground covers (TFC, PCC, and ALF) had more favorable soil characteristics compared to the conventionally tilled systems (CTC and CTS) or the system with no ground cover (CWS), while the management systems in medium- to fine-textured soils (TFC, PCC, ALF, and CTC) had more favorable soil characteristics than the coarse-textured soils (CTS and CWS). At the upper depth, the soil organic matter, a leading indicator of soil quality, was higher in the TFC (29.20 g kg−1) and PCC (21.30 g kg−1), both having permanent cover, than in the CTC (8.63 g kg−1), CWS (6.36 g kg−1), and CTS (8.30 g kg−1). Soil nutrients were generally higher in the PCC and ALF, which had leguminous crops, indicating the beneficial effects of legumes in nutrient cycling of arid soils. Importantly, management impact on most soil characteristics was similar across both depths, indicating that sampling at 0 to 15 cm alone may be sufficient for evaluating the impacts of crop management systems on soil quality. This study shows that management systems, soil, and crop types are factors that need to be considered for sustainable management of soil quality in arid agroecosystems.

Modeling corn growth and root zone salinity dynamics to improve irrigation and fertigation management under semi-arid conditions

Modeling is an advanced technique to study the effects of crop management practices as management scenario simulations in a convenient and economical way. A multi seasonal study was conducted on corn, sown under drip irrigation, to assess its growth under three irrigation intervals (I1: irrigation on daily basis, I2: irrigation on 3rd day and I3: irrigation on 5th day) and three fertigation levels [F1:100 % RFA (recommended fertigation applications), F2:75 % RFA and F3:50 % RFA)] of two types of fertilizers (M1: Imported and M2: Indigenous). The SALTMED model was calibrated and validated, using data collected from experiments, to explore different management scenarios of corn production. The accuracy of the validation process was examined by root mean square error (RMSE), percentage of difference (%D), coefficient of residual mass (CRM) and coefficient of determination (R2). The results showed that corn produced statistically highest plant height (183.7 cm), dry matter (16.9 t/ha), grain yield (8.57 t/ha) and water productivity (1.52 kg/m3) under I1 in comparison to that under other irrigation intervals. Similarly, M1 and F1 produced statistically highest plant height, dry matter, grain yield and water productivity as compared to M2 and other fertigation levels, respectively. SALTMED simulated soil moisture and soil salinity accurately with average values of RMSE, R2 and CRM as 0.013, 0.850 and -0.002, respectively for soil moisture and 0.479, 0.864 and 0.130, respectively for soil salinity. The SALTMED simulations showed good results also for grain yield (RMSE = 0.475, R2 = 0.873, CRM = -0.0013 and highest %D = -4.9 %) and dry matter (RMSE = 0.596, R2 = 0.909, CRM = -0.027 and highest %D = 4.2 %). Overall, it was concluded that corn should be irrigated on daily basis under drip irrigation and fertilized with 100 % RFA. Moreover, the SALTMED model proved to be a useful tool for simulations of different management scenarios regarding corn growth and root zone salinity dynamics with reliable results under semi-arid conditions.

Effect of Crop Management Practices on Crop Growth, Productivity and Profitability of Rice–Wheat System in Western Indo-Gangetic Plains

An experiment was conducted with three managements varied in tillage, crop establishments, residue, fertilizer, water to evaluate crop behaviour, irrigation water use, crop productivity and profitability of crops in an individual and in system mode. Three management systems were conventional system [TPR (transplanted rice)–CTW (conventional-till wheat)], partial CA [TPR–ZTW (zero–till wheat)] and full CA [ZTDSR (ZT direct seeded rice)–ZTW]. Rice plant growth (shoot and root) behaves similarly in CT and ZT based systems up to 40 days after sowing and after that TPR–ZTW recorded higher growth followed by TPR–CTW and lowest with ZTDSR. However, reverse trend in growth was observed with wheat in order of ZTDSR–ZTW > TPR–ZTW > TPR–CTW. Lower NDVI values were observed with ZTDSR and higher values with TPR throughout the crop season. Full CA based wheat recorded higher NDVI values than other management systems during the crop growth period. Higher wheat yield attributing character was recorded with ZTDSR–ZTW and lowest with farmer’s practices (TPR–CTW). On 2-years mean basis, ZTDSR–ZTW system produced similar crop yields to TPR–ZTW and TPR–CTW with 28% less irrigation water and 29% higher returns compared to TPR–CTW. However, TPR–ZTW improved system productivity and net returns by 8 and 37% respectively, compared to TPR–CTW while saving of 14% irrigation water. ZTDSR recorded a yield loss of 10%; while wheat registered a yield gain of 21% with ZTDSR–ZTW. CA based management practices slowed down the DSR crop growth and yield but increased same for wheat crop which is ultimately helpful in sustaining productivity and profitability of rice–wheat system (RWS) in North West India.

Changes in soil surface chemistry after fifty years of tillage and nitrogen fertilization

Knowledge gained on the long-term effects of crop management practices on soil fertility is critical in developing nutrient management strategies to optimize crop yields. This study examined the long-term effects of nitrogen (N) fertilizer application rates (0, 22, 45 and 67kgNha−1) and tillage intensity [conventional tillage (CT), reduced tillage (RT) and no-tillage (NT)] on soil phosphorus (P), micronutrients and soil acidity in a dryland winter wheat (Triticum aestivum L.) – sorghum (Sorghum bicolor L.) – fallow cropping system. Results showed soil organic matter (SOM), iron (Fe) and manganese (Mn) concentrations were greater under NT compared to CT or RT. Similarly, NT (32mgkg−1) increased P accumulation in the upper 7.5cm soil depth compared to CT (21mgkg−1) or RT (26mgkg−1). After 50-yr of tillage and N fertilizer application, pH at the soil surface (0 to 7.5cm) declined markedly with increasing N application, ranging from 6.4 with the unfertilized control to 5.7 when 67kgNha−1 was applied. Averaged across N rates, Δ pH in the soil surface over the 50-yr was greater with NT compared to CT or RT treatments. Iron and Mn concentrations increased with increasing N application rates, possibly due to the decrease in pH associated with N application. Based on our findings, growers adopting NT need to monitor changes in soil surface chemistry and take necessary corrective measures such as liming to maintain satisfactory pH and nutrients levels to optimize crop yields.

Assessing broomrape risk due to weeds in cropping systems with an indicator linked to a simulation model

Integrated crop protection tolerates residual weed floras if they are not harmful for crop production. These weeds can host harmful crop pests, among which parasitic plants such as branched broomrape (Phelipanche ramosa). This holoparasite is responsible for large yield losses in French crops such as oilseed rape. To date, there are no herbicides available to control it. To evaluate ex ante the impact of crop management practices on weed-mediated parasite infection of crops, we developed an indicator calculated from outputs of the weed dynamics model FlorSys. It consists of three components assessing weed impact on (1) stimulation of parasite germination during the whole cropping season, i.e. the potential risk reduction for future crops via a reduction of the parasite seed bank, (2) the stimulation of parasite germination in host crops, i.e. the potential risk increase for the current crop, (3) parasite reproduction on weed plants, i.e. the potential risk increase for future crops. This indicator was then used to predict weed-mediated broomrape risk in cropping systems from six regions from France and one from Spain. Antagonisms and synergies with other indicators of weed-harmfulness for crop production and weed contribution to plant and functional biodiversity were investigated with Pearson correlation analyses. For instance, cropping systems with a high parasite risk also had a high functional biodiversity (e.g. weed-based food offer for bees). Effects of crop management practices on the weed-mediated parasite risk indicator were identified with linear models; regression trees were used to identify the combinations of management practices that maximised or minimised weed-mediated broomrape risk. Parasite risk depended on crop rotation, sowing and harvest dates, tillage, herbicides and mechanical weeding. The lowest risk was observed in fields that were last tilled less than 21days before sowing, with more than 0.6 herbicides per year (i.e. 3 applications in 5 years) with multiple entry modes into the weeds (e.g. leaves and roots) and the last herbicide sprayed no later than 127days before harvest. RLQ analyses were used to identify correlations between weed species traits (Q matrix) and simulated parasite risk (R matrix), via simulated weed densities (L matrix). Early summer-emerging weed species increased parasite risk. No other notable correlations were found, indicating that parasite risk results from a weed community of interacting species, and not simply from individual weed species. An advice table was built to summarize and explain the effects of crop management practices on weed-mediated parasite risk.

Effect of Organic Potato Farming on Human and Environmental Health and Benefits from New Plant Breeding Techniques. Is It Only a Matter of Public Acceptance?

Organic farming practices are commonly thought to reduce the environmental impact of agriculture and to preserve the naturalness of the products. Herein, we report the effect of crop management practices on nutritional and toxicological value of potato tubers. Comparative studies are often controversial and the results are dependent on genotype and methodological approach. Targeted analysis and “omics” strategies are discussed, pointing at the nutritional aspects and the corresponding biological and molecular processes involved. Organic farming supporters still do not accept the use of genetic modification to produce new varieties suited for organic agriculture and crop improvement by genetic engineering still sparks hot debate among various scientific and social factions whose major concern is the possible existence of unintended effects both on human and world health. In this context, the advent of “new plant breeding techniques” has reignited the discussion on genetic engineering and on the compatibility of the new technologies with an eco-friendly agriculture. Could cisgenic and genome-edited potatoes be new good options for organic agriculture? We discuss how these approaches can be used to address food security challenges and to overcome specific problems based on the biological characteristics of potato tubers, producing new varieties that can improve farmers’ profit with a lower impact on public opinion. However, political, ethical, and social fears will probably persist much longer, mainly in Italy, historically a fiercely anti-GM country with a European leadership in organic food production and export.

Climate variability and yield risk in South Asia’s rice–wheat systems: emerging evidence from Pakistan

Rice and wheat are the principal calorie sources for over a billion people in South Asia, although each crop is particularly sensitive to the climatic and agronomic management conditions under which they are grown. Season-long heat stress can reduce photosynthesis and accelerate senescence; if extreme heat stress is experienced during flowering, both rice and wheat may also experience decreased pollen viability and stigma deposition, leading to increased grain sterility. Where farmers are unable to implement within-season management adaptations, significant deviations from expected climatic conditions would affect crop growth, yield, and therefore have important implications for food security. The influence of climatic conditions on crop growth have been widely studied in growth chamber, greenhouse, and research station trials, although empirical evidence of the link between climatic variability and yield risk in farmers’ fields is comparatively scarce. Using data from 240 farm households, this paper responds to this gap and isolates the effects of agronomic management from climatic variability on rice and wheat yield risks in eight of Pakistan’s twelve agroecological zones. Using Just and Pope production functions, we tested for the effects of crop management practices and climatic conditions on yield and yield variability for each crop. Our results highlight important risks to farmers’ ability to obtain reliable yield levels for both crops. Despite variability in input use and crop management, we found evidence for the negative effect of both season-long and terminal heat stress, measured as the cumulative number of days during which crop growth occurred above critical thresholds, though wheat was considerably more sensitive than rice. Comparing variation in observed climatic parameters in the year of study to medium-term patterns, rice, and wheat yields were both negatively affected, indicative of production risk and of farmers’ limited capacity for within-season adaptation. Our findings suggest the importance of reviewing existing climate change adaptation policies that aim to increase cereal farmers’ resilience in Pakistan, and more broadly in South Asia. Potential agronomic and extension strategies are proposed for further investigation.

Effects of Crop Management Practices on Current-Season Spread of Potato virus Y.

The current-season spread of Potato virus Y (PVY) was monitored in 19 fields under various management practices in New Brunswick, Canada, through the 2011 and 2012 growing seasons. The focus of this study was to evaluate the role of seedborne PVY inoculum, aphid vector abundance, and the numbers, timing, and types of insecticide and mineral oil sprays, and to confirm the reliability and forecasting capacity of midseason PVY testing. In each field, 100 to 110 virus-free plants were identified shortly after emergence and were assessed four times from early July to early September (after top-kill) with enzyme-linked immunosorbent assay (ELISA) and reverse-transcription polymerase chain reaction (RT-PCR) to track PVY spread. In addition, tubers harvested during development in August and after top-kill were grown-out in the greenhouse for ELISA testing. PVY spread to selected virus-free plants varied widely, ranging from 0 to 76.2% across all studied fields. Of the 19 fields over two seasons, 10 fields were planted with no detectable seedborne PVY, and they showed 0 to 8.7% (mean 2.9%) PVY spread by harvest. The remaining nine study fields with 0.9 to 5.8% seedborne PVY showed 1 to 76.2% (mean 15.2%) PVY spread by harvest. PVY spread was detected in most fields during midseason testing with ELISA and RT-PCR; all tests correlated well with final PVY rates after top-kill, though RT-PCR detection in developing tubers was most sensitive and correlated. Logistic regression modeling was used to identify major factors in PVY spread, including seedborne PVY, early-season aphid abundance, and the numbers of insecticide and mineral oil sprays. The best-fitting model, constructed using these factors as well as a measurement of July PVY incidence (ELISAJuly), strongly explained PVY spread by harvest, with the most significant management factor being the number of mineral oil sprays supplemented with insecticide used during the growing season. A similar model fitted without the ELISAJuly did not adequately predict ultimate PVY spread. The analysis suggests that mineral oil alone was effective at lowering PVY spread, and more effective when combined with insecticide, particularly when used early in the season. No evidence was found for differences in PVY spread across the eight cultivars used or across the range of mineral oil application rates, whereas some evidence was found for differences in the effectiveness of different insecticide types.

Simulating Dryland Water Availability and Spring Wheat Production in the Northern Great Plains

Agricultural system models are useful tools to synthesize field experimental data and to extrapolate results to longer periods of weather and to other cropping systems. The objectives of this study were: (i) to quantify the effects of crop management practices and tillage on soil water and spring wheat (Triticum aestivum L.) production in a continuous spring wheat system using the RZWQM2 model (coupled with CERES‐Wheat) under a dryland condition, and (ii) to extend the RZWQM2 model results to longer term weather conditions and propose alternate cropping systems and management practices. Measured soil water content, yield, and total aboveground biomass under different tillage and plant management practices were used to calibrate and evaluate the RZWQM2 model. The model showed no impacts of tillage but late planting greatly reduced grain yield and biomass, in agreement with observed differences among treatments. The hydrologic analysis under long‐term climate variability showed a large water deficit (32.3 cm) for spring wheat. Fallowing the cropland every other year conserved 4.2 cm of water for the following wheat year, of which only 1.7 cm water was taken up by wheat, resulting in a yield increase of 249 kg ha−1 (13.7%); however, the annualized mean yield decreased 782 kg ha−1 (43.1%) due to 1 yr of fallow. Other long‐term simulations showed that optimal planting dates ranged from 1 March to 10 April and the seeding rates with optimum economic return were 3.71 and 3.95 × 106 seeds ha−1 for conventional and ecological management treatments, respectively.

Soil Carbon Sequestration by Switchgrass and No-Till Maize Grown for Bioenergy

Net benefits of bioenergy crops, including maize and perennial grasses such as switchgrass, are a function of several factors including the soil organic carbon (SOC) sequestered by these crops. Life cycle assessments (LCA) for bioenergy crops have been conducted using models in which SOC information is usually from the top 30 to 40 cm. Information on the effects of crop management practices on SOC has been limited so LCA models have largely not included any management practice effects. In the first 9 years of a long-term C sequestration study in eastern Nebraska, USA, switchgrass and maize with best management practices had average annual increases in SOC per hectare that exceed 2 Mg C year−1 (7.3 Mg CO2 year−1) for the 0 to 150 soil depth. For both switchgrass and maize, over 50 % of the increase in SOC was below the 30 cm depth. SOC sequestration by switchgrass was twofold to fourfold greater than that used in models to date which also assumed no SOC sequestration by maize. The results indicate that N fertilizer rates and harvest management regimes can affect the magnitude of SOC sequestration. The use of uniform soil C effects for bioenergy crops from sampling depths of 30 to 40 cm across agro-ecoregions for large scale LCA is questionable.

Impact of crop management on weed species diversity and community composition of winter wheat fields in Iran

The aim of this study was to assess the effects of crop management practices on the diversity, structure, and composition of weed communities. A total of 30 fields (15 fields each) in low‐input and conventional farming systems were surveyed in north‐eastern Iran. In the conventional cropping system, both mineral fertilizers and herbicides were applied, while in the low‐input cropping system, the fertilizer was mainly manure and herbicides were avoided. The results showed that the pool of species, species richness, number of unique species, and Shannon's diversity index were greater in the low‐input system than in the conventional system. Both cropping systems had more broad‐leaved species than grasses and more annual species than perennial species. All the multivariate methods of analysis that were applied revealed that the weed community composition was significantly different between the two management types. The low‐input cropping favored herbicide‐susceptible broad‐leaved weeds, legumes, and weeds with biodiversity value, whereas a high proportion of herbicide‐tolerant grasses was found in the conventional fields. The results suggest that low‐input cropping can sustain high weed diversity and abundance.

Soybean Lutein Concentration: Impact of Crop Management and Genotypes

Lutein is a carotenoid with health‐beneficial properties found in soybean [Glycine max (L.) Merr.]. A study was conducted in multiple environments in Quebec, Canada, to determine the effects of crop management practices and genotypes on soybean lutein concentrations. Practices evaluated included seeding rate, row spacing, seeding date, and P and K fertilization; lutein variation and stability among 20 genotypes were also studied. Management practices affected soybean lutein concentration to different degrees. Seeding date had the greatest effect on lutein concentration of all factors evaluated, but response varied greatly between environments. Differences in lutein concentration between seeding date treatments averaged 41%. Seeding rate, row spacing, and P and K fertilization effects were minimal. Increasing the seeding rate from 40 to 60 seed m−2 resulted in a 6% increase in lutein concentration. Response to row spacing and P fertilization treatment was inconsistent and differences between treatments were never >8%. There was no response to K fertilization. Large differences were observed between the 20 genotypes evaluated, with lutein concentrations ranging between 4.1 and 10.9 μg g−1 Despite the presence of significant environmental effects, genotypes with consistently high and stable lutein concentrations were identified. Selection and development of high‐lutein cultivars should be possible; however, environmental factors and crop management practices should be considered in the use of soybean as a source of lutein.

Simulating Long-Term Effects of Nitrogen Fertilizer Application Rates on Corn Yield and Nitrogen Dynamics

Thoroughly tested agricultural systems models can be used to quantify the long-term effects of crop management practices under conditions where measurements are lacking. In a field near Story City, Iowa, ten years (1996-2005) of measured data were collected from plots receiving low, medium, and high (57-67, 114-135, and 172-202 kg N ha-1) nitrogen (N) fertilizer application rates during corn (Zea mays L.) years. Using these data, the Root Zone Water Quality Model linked with the CERES and CROPGRO plant growth models (RZWQM-DSSAT) was evaluated for simulating the various N application rates to corn. The evaluated model was then used with a sequence of historical weather data (1961-2005) to quantify the long-term effects of different N rates on corn yield and nitrogen dynamics for this agricultural system. Simulated and measured dry-weight corn yields, averaged over plots and years, were 7452 and 7343 kg ha-1 for the low N rate, 8982 and 9224 kg ha-1 for the medium N rate, and 9143 and 9484 kg ha-1 for the high N rate, respectively. Simulated and measured flow-weighted average nitrate concentrations (FWANC) in drainage water were 10.6 and 10.3 mg L-1 for the low N rate, 13.4 and 13.2 mg L-1 for the medium N rate, and 18.0 and 19.1 mg L-1 for the high N rate, respectively. The simulated N rate for optimum corn yield over the long term was between 100 and 150 kg N ha-1. Currently, the owner-operator of the farm applies 180 kg N ha-1 to corn in nearby production fields. Reducing long-term N rates from 180 to 130 kg N ha-1 corresponded to an 18% simulated long-term reduction in N mass lost to water resources. Median annual FWANC in subsurface drainage water decreased from 19.5 to 16.4 mg N L-1 with this change in management. Current goals for diminishing the hypoxic zone in the Gulf of Mexico call for N loss reductions of 30% and greater. Thus, long-term simulations suggest that at least half of this N loss reduction goal could be met by reducing N application rates to the production optimum. However, additional changes in management will be necessary to completely satisfy N loss reduction goals while maintaining acceptable crop production for the soil and meteorological conditions of this study. The results suggest that after calibration and thorough testing, RZWQM-DSSAT can be used to quantify the long-term effects of different N application rates on corn production and subsurface drainage FWANC in Iowa.