Suitability of winter canola (Brassica napus) for enhancing summer annual crop rotations in Iowa

Winter canola (Brassica napus) could be a good candidate for enhancing cropping systems in Iowa because of its potential to provide environmental benefits and produce a marketable crop compatible with existing grain production and distribution schemes. However, it is still uncertain whether this crop would be suitable for helping balance environmental and financial goals of conventional cropping systems under the environmental and market conditions unique to Iowa. The work presented in this thesis is an effort to assess the suitability of winter canola for providing environmental benefits while fitting within the logistic and economic constrains of current cropping systems. Based on observations from experimentation in field plots, it is determined that canola can be successfully established in the fall, survive the winter, and regrow in the spring, but adequate conditions during fall growth are crucial. It is estimated that seeding by 31 Aug in the north to 12 Sep in the southeast will allow enough time for adequate growth of canola during the fall in at least half of the years in Iowa. Because these seeding date requirements will likely conflict with standing crops during most years, adjustments to the rotation schemes of conventional rotations are needed. Therefore, two alternative systems are proposed, and their economic profiles are studied. Findings from this economic analysis suggest that these rotation alternatives produce relatively less net returns than the conventional corn (Zea mays L.)- soybean (Glycine max (L) Merr.) rotation, throughout a range of market and canola yield scenarios. Based on these results, it is determined that although winter canola can provide some environmental and economic enhancements to summer annual crop rotations in Iowa, but the specific situations in which canola can fit these rotations are limited. Nonetheless, more research is needed to fully understand the productivity potential of winter canola in Iowa, before counting these as feasible alternatives for producers in this state

Estimated Costs of Production for Winter Canola in Iowa

Canola is a productive crop commonly grown in regions outside the Midwestern Corn Belt for its high-quality, edible oil. The oilseed is traded in global commodity markets and its price has seen significant increases during the last decade, primarily due to a steady domestic demand for vegetable oil and strengthening international demand for Canadian canola (1). Findings from our field studies indicate that winter varieties of canola planted in early fall in Iowa (mid-August to early-Sept) have the potential to overwinter and be harvested in mid-July (2). For producers who wish to incorporate alternative crops into their rotation, winter canola may be a good candidate following spring grains (e.g. oats, spring wheat) in a rotation. Yields of winter canola in the U.S. typically range between 0 and 3,600 lb per acre (10 percent moisture) averaging at about 1,900 lb per acre (3). Canola can be seeded using a small-grain drill (4) or conventional row crop planters with row spacing of 15-30 inches, although decreases in yield from 0-10 percent have been observed for wide row spacing (5). Canola typically uses less nitrogen (N) than corn, and slightly more than wheat. Additionally, split N applications are recommended with about 30-50 percent applied at pre-planting, and the balance top-dressed in the spring. The crop can be harvested by direct combining using a “draper” header, although shattering can cause yield losses. Alternatively, the crop can be swathed and then harvested. Swathing helps to speed up dry down and reduces losses due to windstorms and hail. Winter canola is not a grass or legume (canola is in the Brassica family) and it has a winter annual growing cycle. Thus, including this crop in an Iowa rotation could provide more flexible opportunities to rotate herbicide chemistry and pest control strategies. Moreover, some evidence suggests that Brassica species produce chemical compounds that have the potential to control some soil-borne pests and even some weeds (6). Additionally, the winter canola canopy may help to protect soil from erosion during the winter months, and roots can actively take up nutrients, preventing their loss into waterways

Suitability of winter canola (Brassica napus) for enhancing summer annual crop rotations in Iowa

Winter canola shows promise as an addition to crop rotations in Iowa. This project determined optimal seeding dates for this cover crop and explored practices to enhance production. It was estimated that the latest Iowa seeding date varies from around August 31 in the north to September 12 in the southeast

Suitability of winter canola (Brassica napus) for enhancing summer annual crop rotations in Iowa

What are the prospects for winter canola as an alternative crop for Iowa farmers? This project examined the economics and costs/benefits of adding canola as a third crop or a cover crop in rotations

Root to shoot and carbon to nitrogen ratios of maize and soybean crops in the US Midwest

Root traits are important to crop functioning, yet there is little information about how root traits vary with shoot traits. Using a standardized protocol, we collected 160 soil cores (0−210 cm) across 10 locations, three years and multiple cropping systems (crops x management practices) in Iowa, USA. Maximum root biomass ranged from 1.2 to 2.8 Mg ha−1 in maize and 0.86 to 1.93 Mg ha−1 in soybean. The root:shoot (R:S) ratio ranged from 0.04 to 0.13 in maize and 0.09 to 0.26 in soybean. Maize produced 27 % more root biomass, 20 % longer roots, with 35 % higher carbon to nitrogen (C:N) ratio than soybean. In contrast, soybean had a 47 % greater R:S ratio than maize. The maize R:S ratio values were substantially lower than literature values, possibly due to differences in measurement methodologies, genotypes, and environment. In particular, we sampled at plant maturity rather than crop harvest to minimize the effect of senescence on measurements of shoots and roots. Maximum shoot biomass explained 70 % of the variation in root biomass, and the R:S ratio was positively correlated with the root C:N measured in both crops. Easily-measured environmental variables including temperature and precipitation were weakly associated with root traits. These results begin to fill an important knowledge gap that will enable better estimates of belowground net primary productivity and soil organic matter dynamics. Ultimately, the ability to explain variation in root mass production can be used to improve C and N budgets and modeling studies from crop to regional scales

Understanding the 2016 yields and interactions between soils, crops, climate and management

Several technologies to forecast crop yields and soil nutrient dynamics have emerged over the past years. These include process-based models, statistical models, machine learning, aerial images, or combinations. These technologies are viewed as promising to assist Midwestern agriculture to achieve production and environmental goals, but in general, most of these technologies are in their initial stages of implementation. In June 2016 we launched a web-tool (http://crops.extension.iastate.edu/facts/) that provided real-time information and yield predictions for 20 combinations of crops and management practices. Our project, which is called FACTS (Forecast and Assessment of Cropping sysTemS), takes a systems approach to forecast and evaluate cropping systems performance. In this paper we report FACTS yield predictions accuracy against ground-truth measurements and analyzing factors responsible for achieving 200-240 bu/acre corn yield and 55-75 bu/acre soybean yields in the FACTS plots in 2016

Water availability, root depths and 2017 crop yields

During 2016 and 2017, June-July precipitation was below normal in many parts of Iowa creating midseason concerns about potential yield loss due to water stress. However, these concerns were not realized. In contrast, 2016 and 2017 crop yields over-performed yields obtained in many years with average of above average June-July precipitation. In Iowa, deep root systems, high soil water storage capacity, and shallow water tables are common explanations for high yields in years with below normal precipitation. How deep can roots grow? How much does groundwater contribute to the yields? To answer these questions and more, the Forecast and Assessment of Cropping sysTemS (FACTS) project was established in 201