• Energy Research

The incorporation of cover crops into the maize (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation in the U.S. upper Midwest may improve sustainability. Long, cold winters in the region make identifying successful cover crop species and management practices a challenge. Two experiments were conducted in Minnesota, USA from fall 2016 through spring 2019 to examine the effect of cover crops interseeded at four- to six-leaf collar (early-interseeded) and dent to physiological maturity (late-interseeded) on biomass and grain yield of maize. Annual ryegrass (Lolium multiflorum L.) and cereal rye (Secale cereale L.) were evaluated as monocultures and in mixtures with crimson clover (Trifolium incarnatum L.) and forage radish (Raphanus sativus L.). Differences in canopy cover and biomass of late-interseeded cover crops were observed at the southernmost location in 2018. Additional accumulated growing-degree days in fall 2018 did not translate into increased cover crop canopy coverage of late-interseeded cover crops. Differences in cover crop canopy cover and biomass of early-interseeded cover crops were observed by fall frost at all locations in 2017 and at the northernmost location in 2018. Cover crop canopy cover and biomass at termination before planting maize, soil moisture at maize planting as well as maize aboveground biomass and yield were not affected by spring cereal rye regrowth of cover crops late-interseeded the previous year. Similarly, early-interseeded cover crops did not affect maize aboveground biomass or yield. We attribute these results to limited cover crop growth. This highlights the potential of a variety of cover crop strategies interseeded into maize in the U.S. upper Midwest; however, efforts to fine-tuning cover crop management and weather conditions are needed to benefit from such practice.

Meeting demand for food, fiber, feed, and fuel in a world with 9.7 billion people by 2050 without negative environmental impact is the greatest scientific challenge facing humanity. We hypothesize that this challenge can only be met with current and emerging technologies if guided by proactive use of a broad array of relevant data and geospatial scaling approaches to ensure local to global relevance for setting research priorities and implementing agricultural systems responsive to real-time status of weather, soils, crops, and markets. Despite increasing availability of field-scale agricultural data, robust spatial frameworks are lacking to convert these data into actionable knowledge. This commentary article highlights this knowledge gap and calls attention to the need for developing robust spatial frameworks that allow appropriate scaling to larger spatial domains by discussing a recently developed example of a data-driven strategy for estimating yield gaps of agricultural systems. To fully leverage research on sustainable intensification of cropping systems and inform policy development at different scales, we call for new approaches combining the strengths of top-down and bottom-up approaches which will require coordinated efforts between field scientists, crop modelers, and geospatial researchers at an unprecedented level.

Rice blast is a serious fungal disease of rice (Oryza sativa L.) that is threatening global food security. It has been extensively studied due to the importance of rice production and consumption, and because of its vast distribution and destructiveness across the world. Rice blast, caused by Pyricularia oryzae Cavara 1892 (A), can infect aboveground tissues of rice plants at any growth stage and cause total crop failure. The pathogen produces lesions on leaves (leaf blast), leaf collars (collar blast), culms, culm nodes, panicle neck nodes (neck rot), and panicles (panicle blast), which vary in color and shape depending on varietal resistance, environmental conditions, and age. Understanding how rice blast is affected by environmental conditions at the cellular and genetic level will provide critical insight into incidence of the disease in future climates for effective decision-making and management. Integrative strategies are required for successful control of rice blast, including chemical use, biocontrol, selection of advanced breeding lines and cultivars with resistance genes, investigating genetic diversity and virulence of the pathogen, forecasting and mapping distribution of the disease and pathogen races, and examining the role of wild rice and weeds in rice blast epidemics. These tactics should be integrated with agronomic practices including the removal of crop residues to decrease pathogen survival, crop and land rotations, avoiding broadcast planting and double cropping, water management, and removal of yield-limiting factors for rice production. Such an approach, where chemical use is based on crop injury and estimated yield and economic losses, is fundamental for the sustainable control of rice blast to improve rice production for global food security.

Six cover crop treatments were interseeded into maize at two distinct timings: at the four to six-leaf collar stage and at physiological maturity. The canopy cover and biomass of cover crops, soil moisture at planting maize, and maize biomass and yield were evaluated to determine the potential impacts of interseeded cover crops on maize productivity. The data is saved as .csv files and can be viewed in Microsoft Excel workbook and/or R statistical software. The data was collected at field and entered into master files, from which the data to create the .csv files was taken.

Nitrogen (N) fertilizer plays an important role in wheat yield, but N application rates vary greatly, and there is a lack of data to quantify the residual effects of N fertilization on soil N availability. A 17-yr experiment was conducted in a semiarid area of the Loess Plateau of China to assess the effects of N fertilization on spring wheat (Triticum aestivum L.) grain yield, N uptake, N utilization efficiency, and residual soil nitrate. Treatments included a non-N-fertilized control and annual application of 52.5, 105.0, 157.5, and 210.0 kg N ha−1 in the first two years (2003 and 2004). In the third year (2005), the four main plots with N fertilizer application were split. In one subplot, N fertilization was continued as mentioned previously, while in the other subplot, N fertilization was stopped. The concentration of NO3-N in the 0–110 cm depth soil layers was significantly affected by N application, with higher N rates associated with greater soil NO3-N concentration. With the annual application of N over 17 years, residual soil NO3-N concentration in the 100–200 cm soil layer in the last study year was significantly greater than that in the non-N-fertilized control and was increased with rate of N application. There was a significant positive relationship of soil NO3-N in the 0–50 cm and 50–110 cm soil layers at wheat sowing with wheat grain N content and yield. Wheat grain yield in the third year (2005) was significantly, i.e., 22.57–59.53%, greater than the unfertilized treatment after the N application was stopped. Nitrogen use efficiency decreased in response to each increment of added N fertilizer, and was directly related to N harvest index and grain yield. Therefore, greater utilization of residual soil N through appropriate N fertilizer rates could enhance nitrogen use efficiency while reducing the cost of crop production and risk of N losses to the environment. For these concerns, optimum N fertilizer application rate for spring wheat in semiarid Loess Plateau is about 105 kg N ha−1, which is below the threshold value of 170 kg N ha−1 per year as defined by most EU countries.

AbstractAgriculture requires a synergetic improvement in production profitability, long-term viability, and environmental health in the presence of abiotic (i.e., uncontrollable weather, input costs, and product prices) and biotic (i.e., weed pressure and disease infestation) stresses. A “robust” agroecosystem can enhance synergetic improvements by alleviating these stresses, but it is unknown how system robustness can be achieved in a systemic manner. Here, for the first time, we demonstrate that crop diversification can significantly enhance system robustness. An 8-year crop rotation study was conducted, in which 3-year crop sequences were repeated for two cycles, with the first cycle from 2010 to 2012 and the second from 2014 to 2016; each cycle began with a wheat (Triticum aestivum L.) crop, and pea (Pisum sativum L.), lentil (Lens culinaris Medik.), and mustard (Brassica juncea L.) were included in the rotation, and chickpea (Cicer arietinum L.), a N2-fixing legume susceptible to weed pressure and the foliar disease Ascochyta blight, was the last crop in each of the two cycles. Crop diversification improved system resistance to biotic stresses, and that chickpea in the diversified lentil-wheat-chickpea system had the lowest weed biomass and foliar disease severity among rotation systems. Chickpea in the diversified pea-mustard-chickpea system recovered from severe weed pressure by the end of the second cycle in 2016. Diversified systems increased resistance and resilience from abiotic stresses and improved the constancy in crop productivity across rotation cycles, compared to the less diversified systems. Quantitative assessments show that the most diversified systems had a 14% advantage in system robustness. We conclude that diversifying crop rotation improves system robustness through enhancing crop resistance to and resilience from biotic-induc ed disturbances and increasing the constancy of crop productivity while facing disturbance.

Corn (Zea mays L.) stover and cobs remaining after grain harvest can serve as a feedstock for cellulosic ethanol production. Field trials were conducted at two locations in Minnesota over three years to determine how corn cellulosic yield composition and ethanol yield are influenced by tillage system [chisel tillage (CT), strip-tillage (ST), and no-tillage (NT)] and fertilizer N rate (0, 45, 90, 134, 179, and 234 kg N ha−1). Stover biomass yield, C and N concentrations and content, and potential ethanol yield increased with increasing fertilizer N rate. Stover biomass yield, C content, and potential cellulosic ethanol yield were less with NT than CT and ST by ≥9, 8, and 8 %, respectively. Theoretical ethanol yield of stover was maximized at a fertilizer N rate lower than the economically optimum N rate (EONR) for grain yield. Cob biomass yield, C concentration and content, N concentration, and potential ethanol yield increased with fertilizer N rate, but not at the same magnitude observed for stover. Tillage system did not influence cob biomass yield, C and N concentrations and content, or potential ethanol yield. These results demonstrate that biomass and ethanol production of stover and cobs can be affected by N and tillage management. Cobs may be a more viable feedstock option than stover because nearly all measured variables were less sensitive to management and their harvest removes less C and N from a field compared to full harvest of combined cobs and stover.

AbstractIn arid regions, higher irrigation quota for conventional farming causes substantial conflict between water supply and demand for crop production. Innovations in cropping systems are needed to alleviate this issue. A field experiment was conducted in northwestern China to assess whether straw and plastic managements in wheat/maize intercropping could alleviate these issues. Integrating no tillage with two-year plastic and straw mulching (NTMI2) improved grain yields by 13.8–17.1%, compared to conventional tillage without straw residue and annual new plastic mulching (CTI). The NTMI2 treatment reduced soil evaporation by 9.0–17.3% and the proportion of evaporation to evapotranspiration (E/ET) by 8.6–17.5%, compared to CTI. The NTMI2 treatment weakened wheat competition of soil moisture from maize strip during wheat growth period, and enhanced wheat compensation of soil moisture for maize growth after wheat harvest, compared with CTI. Thus, soil water movement potential of NTMI2 was lowest during wheat growth period, but it was highest during maize-independent growth stage after wheat harvest. The NTMI2 treatment increased evapotranspiration before maize silking, decreased from maize silking to early-filling stage, and increased after the early-filling stage of maize, this effectively coordinated water demand contradiction of intercrops at early and late stages. The NTMI2 treatment improved WUE by 12.4–17.2%, compared with CTI. The improved crop yields and WUE was attributed to the coordinated water competition and compensation, and the decreased soil evaporation and E/ET.