Roller-Crimping Cover Crops on Irrigated Organic Cropland

Objective 1 - Determine best performing species and varieties of winter cereal grain to use as a rolled-down mat in the Western Slope region of Colorado.

Several species - winter rye, winter triticale, winter wheat and winter barley - and varieties within each have been used in organic no-till pulse studies. However, as suggested by a review published by Vincent-Caboud et al, in 2019, “future research should focus on (i) screening species and cultivars to identify cover crop and crop combinations that optimize cropping system performance [...].”. A research paper published by the same authors in 2019 showed differences in soybean yield and weed emergence with various winter rye and winter triticale varieties, which had produced comparable biomass amounts.

Winter rye and winter triticale are proving to be the best-performing species. At David Harold’s farm, in addition to a tilled plot for control, we will plant at least two varieties of each species and assess their performance.

Protocol:

1/ Spring Stand

• Evenness, assessed with computing the greenness from UAV imagery, will determine if there was poor germination or poor over-wintering. Hired drone photographer will take UAV photos and TA will analyze them.
• Tillering, assessed by random tiller counts across plots, performed by PI, TA, and Educators.

2/ Biomass at termination, according to a review by Silva and Delate, 2017 a good stand will exceed 8,000 kg of dry matter of winter cereal per hectare. PI, TA, Educator and Intern will clip above ground winter cereal biomass, air dry it on farm, and weigh samples. Léa will enter and analyze data.

3/ Weed control will be assessed in August of each growing season. PI, TA, Educator and Intern will clip above ground weed biomass in random plot places (including tiller control), air dry it on farm and weigh samples. Léa will enter and analyze data.

Objective 2 - Determine best planting date of winter cereal grain

A determining factor in obtaining 8,000 kg per ha of winter cereal, or more, at the time of planting is the cereal planting date. A study by Mirsky et al showed that winter cereal cover-crop biomass increased approximately 2,000 kg of dry matter per ha from latest to earliest fall planting dates (August 25-October 15).

Olathe CO, is qualified as a USDA hardiness zone 6b, same as Kutztown PA, where Rodale Institute’s main farm is located. There, for a successful organic no-till soybean crop, winter cereal should be planted before October 10 (verbal communication with Dr. Andrew Smith, COO, Rodale Institute). While a later planting date is desirable to allow more flexibility in the choice of the preceding crop, planting too late will result in poor cereal stand and biomass production. At David’s farm, we will plant winter cereals at a minimum of two different dates between September 15 and October 15.

To assess the performance of different seeding dates, we will use the same protocol described in Objective 1.

Objective 3 - Determine if roller-crimper is needed for adequate termination of winter cereal

Adequate timing of the roller-crimping has been documented as late anthesis into early milk stage: “Cereal rye biomass peaked at the late dough stage but optimal mechanical control was obtained between 50% anthesis and early milk stages.” (Keene et al, 2017). Adequate termination is critical to improve water use efficiency of the whole system. A poorly terminated cover crop will continue evapotranspiration at the crop’s detriment. 

While roller-crimpers have been a tool of choice for cover crop termination in the organic no-till system, there is anecdotal evidence* from Midwestern farmers that other, non-specialized tools could be used if termination timing is adequate. In this study, we will be comparing the quality of cover crop termination using a roller-crimper or a cultipacker at late-anthesis, early milk stage of winter cereal development.

Protocol:

1/ Computing the greenness of the mat from UAV imagery taken 5,10 and 15 days after termination. Hired drone photographer will take UAV photos and TA will analyze them.

2/ Measure water use efficiency. In August, PI, TA, Educator and Intern will collect crop above ground biomass at random locations of each treatment (including the tilled control). TA will pair the crop biomass data with the water input date collected using the flow meter to calculate water use efficiency of each winter cereal.

* Anecdotal evidence gathered by Léa Vereecke during her 6 years of work across Midwestern States with organic farmers implementing the practice.

Objective 4 - Pinto beans seed saving

“[...] cultivar selection and breeding for cash crops adapted to Cover Crop Based Rotational Tillage (CCBRT) remains a component of the system where a dearth of information exists. The value of breeding crops for specific organic environments is increasingly recognized. [...] cultivars that can withstand cooler soil temperatures, establish through the thick cover crop residue, and withstand a narrow row spacing could provide specific trait advantages to improve performance in the CCBRT system.” (Silva and Delate, 2017)

David Harold and his peers have experience with seed-saving to breed for their specific growing conditions. Crop seeds will be saved from the first crop’s harvest to plant the second year. If the system shows promising results by the end of the project, David and peers will continue implementing and saving seeds.

Objective 5 - Measure water use efficiency/infiltration as influenced by rolled-down cereal

See “Relevance to sustainable agriculture” section for references on relationship between no-till into rolled-down cereal mat and water use efficiency.

Protocol:

1/ On-farm visual observation of soil surface condition: establish a rating system of surface soil moisture and assess it monthly  (PI, TA and/or Educators and/or Intern)

2/ Infiltration rate using infiltration rings, monthly, PI, TA and/or Educators and/or Intern will insert infiltration rings into the soil to a depth of two inches and fill them with water to measure the rate of infiltration in the rolled-down mat and the bare soil.

3/ Protocol 2/ of Objective 3

Objective 6 - Compare weed control under tilled and no-till organic pinto bean production

Protocol:

see Objective 1, 3/