Agriculture faces many intractable problems in the near future that are unprecedented in their scale and global impact. Population growth, shifts in consumption and non-food uses of agricultural products, climate change, and degradation of natural capital threaten global food security. To meet greater demand without further compromising environmental integrity, farmers will needs to increase production while regenerating and improving existing cropland (Foley et al. 2011). Perennial crops are a possible solution to some of these problems due to their reduced need for mechanical, material, and labor inputs, potential for production on marginal agricultural lands, and ability to provide ecosystem services that are not available from annuals, such as year-round erosion control (Asbjornsen et al. 2012; Zhang et al. 2011). Perennial grains are a key component in efforts to increase the proportion of perennial crops in agricultural production, as annual grain crops are grown on 70% of global agricultural land and make up 80% of the global food supply (Pimentel et al. 2012).
While the benefits of perennial grain crops are attractive, development and adoption of perennial grain cropping systems relies on solving a number of agronomic issues that negatively impact their economic viability. Chief among these issues is significantly lower grain yields from perennial grains compared with annual analogs (Jaikumar et al. 2012). Substantial progress has been made in breeding higher-yielding cultivars of perennial wheat (DeHaan et al. 2014) and perennial rye (Acharya et al. 2004), but there has been less investigation of best practices for perennial grain crop management in the field. However, as little as 30% of yield increases in annual wheat can be attributed to genetic improvement over the past several decades (Anderson et al. 2005), suggesting that agronomic practices have a large effect on cropping system performance. Optimization of management strategies might also have a large impact on improving perennial grain productivity and thus profitability.
The purpose of this project is to investigate the impact of stand renovation via strip tillage and strip intercropping grain legumes on the productivity and profitability of intermediate wheatgrass cv ‘Kernza’ (Thinopyrum intermedium) and perennial rye cv ‘ACE-1’ (Secale cereale x S. montanum) perennial grain crops in the Northeast. Kernza is a variety of intermediate wheatgrass domesticated for use as a grain crop by researchers at the Land Institute in Salina, KS. Breeding progress has recently reached a point where Kernza is beginning to enter small-scale commercial production through partnerships between researchers, growers, and processors interested in selling products made with Kernza to consumers interested in sustainably grown food (Karnowski 2017). As an example, Patagonia Provisions recently release Long Root Ale, a craft beer made from Kernza and marketed with the ecosystem services provided by Kernza as a key selling point (Lubofsky 2016). ACE-1 is a hybrid perennial rye developed by researchers at the Agriculture and Agri-Food Canada Research Centre in Lethbridge, AB, Canada, originally intended as a forage crop but now also being utilized for food-grade grain production. We believe that Kernza and ACE-1 present opportunities for farmers in the Northeast to meet demands for local grain production and take advantage of the new market for perennial grain products while diversifying their cropping systems, decreasing costs through more efficient use of land, labor, and material inputs, and protecting their soils and the environment.
Despite the potential to transform agriculture, there are still several agronomic issues to be addressed in Kernza cropping systems. One major issue is that yields tend to decrease in mature Kernza stands after two to three years of growth. This effect is believed to be caused by vigorous root growth that restricts tillering and reproductive capacity within a few years of planting (Jungers et al. 2017). We are interested in how strip tillage might contribute to mitigating this problem via root pruning and subsequent stimulated growth of mature Kernza plants. In addition, grass-legume intercrops including intermediate wheatgrass have been shown to be more productive and weed suppressive than monocultures (Weik et al. 2002). We hypothesize that including grain legumes may provide similar benefits while also enhancing overall profitability of the system via sale of the legume crop.
To better understand the effects of strip tillage and intercropping grain legumes on the productivity and profitability of Kernza perennial wheat cropping systems we will pursue the following research objectives:
1) Quantify the effects of strip tillage and intercropping on Kernza and grain legume biomass productivity and yield.
2) Quantify the effects of both strip tillage and intercropping on weed density and weed species composition.
3) Conduct economic analysis and determine effects of strip tillage and grain legume intercropping on overall cropping system profitability.
4) Monitor and compare Kernza and grain legume growth to inform planting schedules that allow for synchronous maturity and harvesting.
Based on preliminary research results from the 2017 field season the proposed research plan has been split into two separate experiments, one that will investigate intercropping field peas with two perennial small grain varieties, intermediate wheatgrass cv ‘Kernza’ and perennial rye cv ‘ACE-1’, and another that will investigate the effects of the timing of strip tillage on the renovation of established Kernza stands. This fall the intercropping experiment was planted and fall strip tillage was performed in the tillage experiment. Details on these two experiments and how they differ from the original proposal are provided below.
In order to investigate the potential benefits of intercropping grain legumes with perennial small grains we established a new field experiment in Fall 2017 using a split-plot, spatially balanced complete block design. Perennial grain and field pea monocultures and intercrops are the whole plot treatments and oats planted as a winter-killed nurse crop is the split-plot treatment (PGP_plotMap). The two perennial grains and the oat nurse crop were planted September 19, 2017, and field peas will be planted April 2018. Intercrops are to be planted as a replacement series, with alternating rows of grain and peas at a 7.5 in row spacing. This experiment differs from the original proposal in several ways. Perennial rye is an additional perennial small grain crop that we will be investigating. As we do not have established perennial rye stands available for this experiment, the perennial grain crops are newly planted, and thus tillage was uniform and is not a treatment. We have also added the use of oats as a winter-killed nurse crop for the perennial grains as a split-plot treatment in order to determine whether it can improve the perennial grains’ ability to compete with weeds during the establishment year. This additional research question was developed based on results of our other perennial grain field experiments and information provided by collaborators at the University of Minnesota and the University of Wisconsin. Soybean has been removed as a possible legume intercrop due to its late maturation relative to the perennial grains which caused significant harvest complications during our preliminary trial during the 2017 field season.
Due to our inability to examine the effects of strip tillage as a tool for stand renovation in the intercropping experiment described above, we have also begun a separate tillage experiment in the 3.5 year-old Kernza stand we had originally intended to use for the combined intercropping/tillage experiment that we had originally proposed. In the revised tillage experiment we will be investigating the effects of the timing of strip tillage on Kernza productivity using a randomized complete block design with fall tillage, spring tillage, and a no-till control as treatments (see attached file: NEW_tillage_plotMap). The fall tillage treatment was done in early October 2017 and the spring tillage treatment will be done in April 2017 prior to Kernza jointing. This experiment differs from the original proposal in that we have added a fall tillage treatment based on our experiences using strip tillage in established Kernza stands in spring 2017. Spring tillage must be done prior to Kernza jointing to avoid excessive damage to the plant that inhibits grain production, but timing of spring tillage is complicated by wet field conditions that have become more common and problematic in the northeast in recent years. Fall tillage may have similar renovation effects as spring tillage, while avoiding these potential timing issues and also reducing workload on farmers during the busy spring planting season.
Data collection in both experiments will be similar to what was described in the original proposal, with grain yield, crop biomass, and weed biomass as the response variables being measured. Data collection will begin in July 2018 as originally planned.
Education & Outreach Activities and Participation Summary
No education or outreach activities related to this project have been done at this point. The project will be discussed at a meeting with farmers who are collaborating with our lab on perennial grain research that is planned for January 2018, and it is anticipated that a presentations on our combined perennial grain research program, including this project, will be given at multiple conferences, field days, and farmer meetings during 2018.