No Till Notes: 'American Society of Agronomy'

I was invited to do a presentation via webinar by the American Society of Agronomy. They sponsored a three series webinar titled “Replacing Fallow with Cover Crops and Annual Forages in the Semi-Arid Central Great Plains”.

The other participants presenting during this three series webinar included Dr. Dave Nielsen, research agronomist, ARS in Akron, Colorado, Dr. John Holman, cropping systems agronomist, Kansas State University, Garden City, Kansas, and Dr. Clain Jones, soil fertility extension specialist, Montana State University, Dietrich Kastens, producer from Herndon, Kansas, and myself.

The researchers from each area have done some extensive research in an effort to evaluate the performance of using cover crops as a green fallow replacement to more traditional fallow in winter wheat/ summer fallow cropping systems used primarily in the Great Plains. This research was conducted from two to eight years at the various sites.

There is a significant difference between the sites where the research was conducted in precipitation and levels of evaporation. There is quite a difference in the levels of evaporation rates between Kansas and Montana. Kansas has also experienced a prolonged drought during a portion of the research conducted as well as the Colorado site.

The researchers focused on the amount of moisture required to grow various cover crops as a single species or in combinations or cocktail mixes. The researchers also studied termination dates of the different cover crops and the amount of moisture used to produce the cover crop. They also looked at the amount of moisture available in the soil at winter wheat seeding.

The results of this research showed a general reduction in grain yields following cover crops used as a fallow replacement. The reduction of yield and protein in the grain crops was a result of the cover crop water use during the growing season along with some available nitrogen reduction in the soil following the cover crops.

The further north the trials were conducted the less the detrimental effects were on the grain yields. The higher annual precipitation rates were in the southern plains areas but the higher precipitation was offset by the increase in pan evaporation rates. The lower evaporation rates in the northern studies seemed to reduce the negative effects of the moisture used by the cover crops.

An interesting result came out of Dr. Jone’s long term studies in Montana where a pea cover crop has been grown as a fallow replacement over an eight year study. The results of this research seem to indicate that over time the green cover crop planted as a fallow replacement with termination at first bloom has increased grain yields as the study as gone along. It appears that over time the planting of cover crops, in particular peas, there is an increase in available nitrogen resulting in higher grain yields and lower nitrogen requirements to produce the crop when compared to fallow.

Dietrich Kastens on farm research showed dramatic yield reduction in his corn yields where he planted cover crops following his winter wheat harvest the previous summer. Dietrich’s main concern with the cover crops is the overall loss of residues in the field following the cover crops. Dietrich stressed the importance of residues in his system to provide the armor to the soil surface needed to protect the soil surface from wind erosion and lower soil moisture evaporation rates.

During my presentation I feel the best way for us to achieve the positive benefits from cover crops for providing improved soil health while still maintaining the residues to protect the soil from our harsh environment is to plant diversified forage crops and graze them as part of a crop rotation. I think there is a place in our crop rotations for forage crops to graze livestock. The forage crop is 50% grazed and 50% is left to cover and feed the soil.

I feel there is need for more long term research on utilizing cover crops and forage crops across the Great Plains. I think there is a place in our crop rotations to plant diversified forage crops which will provide long term benefits to our soil and improve the profitability of our farming and ranching operations.