Assessing Productivity and Ecosystem Contributions of a Perennial Grain Crop

Abstract:

The growing interest in perennial grain production largely stems from Field Image1 agricultural stakeholders wanting to improve soil health, protect freshwater supplies, reduce input costs, and mitigate global climate change. In recent studies conducted in the Midwest, the novel perennial grain crop known as Kernza ( Thinopyru m intermedium ), has shown the ability to decrease nitrate leaching, increase labile soil carbon, exhibit a high whole – crop NUE, and sequester more carbon in its biomass than annual wheat. Although the ecological benefits observed from the cultivation of perennial grains are promising, recent studies comparing this crop to annual wheat have lacked a good control for the effect of tillage , and there has yet to be adequate research published on how this perennial grain performs in Mediterranean environments. Thus, grower confidence in this crop may be restricted to regions where perennial grain research is taking place (i.e. the Northeast and Midwest) and the mechanisms behind Kernza’s potential to improve soil ecosystem services are not yet clearly defined.

My research seeks to determine if Kernza is a viable agronomic crop for the Mediterranean climate of California and to expand on existing knowledge concerning Kernza’s potential to sequester carbon and improve soil ecosystem services. More specifically, over the course of three years, the objectives of this research are to: 1) determine if the quantity and lability of soil carbon and nitrogen are a function of the plant type and its associated microbial community, tillage, water, nitrogen fertilization, or a combination of factors ; 2) assess whether Kernza is a practical crop choice for specialty crop growers, growers interested in improving soil health, or growers interested in implementing Kernza on marginal land ; and 3) evaluate if carbon sequestration on a Yolo silt loam in a Mediterranean environment is a function of the plant type and its associated microbial community, tillage, water, nitrogen fertilization, or a combination of factors. An array of soil carbon, nitrogen, and microbial analyses such as permanganate oxidizable carbon, potentially mineralizable nitrogen, and total phospholipid fatty acids will be conducted to address the first objective. To address the second objective, grain yield, aboveground biomass, and harvest index will be tracked and soils from select treatments will be analyzed at the Cornell Soil Health Assessment lab. For the last objective, SOC and/or indicators of C sequestration (i.e. soil aggregation or carbon use efficiency) will be monitored in soils from select treatments and compared to baseline samples.

This study takes place at UC – Davis’s Russell Ranch Sustainable Field Image 2 Agriculture Facility — a long – term research trial in Davis, California that is comprised primarily of Yolo silt loam. We implemented a split – plot randomized complete block design with plant species (annual wheat and Kernza) and tillage (till and no – till annual wheat) as a whole – plot treatment, irrigation as a subplot treatment, and nitrogen fertilization ( 0 – 150 kg N/ha) as a sub – sub plot treatment. This design allows us to answer our questions regarding Kernza’s productivity and the mechanisms behind its potential contribution to soil ecosystem services while controlling for tillage.