Last week I introduced some of Herndon, Kan., no-tiller Dietrich Kasten’s water-use efficiency data that was presented at a past conference. Dietrich had a water use efficiency rating of 33% for a winter wheat/summer fallow rotation.

He arrived at this rating by using the total amount of precipitation received, on average, for the total length of the rotation (42.98 inches), subtracted the amount of moisture required for vegetative growth (10 inches), then determined the amount of moisture required to produce 50 bushels of wheat which is the average wheat crop for traditional winter wheat/summer fallow in their area.

Each additional inch of moisture above the 10 inches required for vegetative growth will produce 4.6 bushels of wheat. Fifty bushels of winter wheat requires 10.86 inches of moisture, in addition to the 10 inches for vegetative growth.

This crop rotation of winter wheat/summer fallow receives 42.98 inches of precipitation, uses 10 of those inches for vegetative growth, uses 10.86 inches for grain production, and has 22.11 inches of precipitation lost to evaporation, leaching or weed competition.

Using this same model for other crop rotations, Dietrich compared similar systems such as winter wheat/corn/summer fallow and determined with 60-bushel wheat yields, his efficiency in producing the wheat crop jumped to 52%.

Through extensive on-farm research they’ve determined there is a 10-bushel increase in their wheat yields from 50 bushels/acre in a wheat/summer fallow rotation to 60 bushels/acre in a wheat/corn/summer fallow system.

Winter wheat following winter wheat had an efficiency of 76%, with an expected yield of 40 bushels/acre. The efficiency was higher due to a shorter fallow period from winter wheat harvest until the planting of winter wheat in September.

Corn following winter wheat had an efficiency of only 40% during this 15-month period from winter wheat harvest until corn maturity. During this time he receives on average 29.5 inches of precipitation and raises 100 bushels of corn per acre. The 100-bushel corn crop needs 18.42 inches of moisture to produce this yield.

Corn requires 10.9 inches for vegetative growth, and for each additional inch, corn yields increase by 13.3 bushels per acre. There is a loss of 11.08 inches of precipitation from this cropping system.

Dietrich has added field peas into his cropping rotation, replacing the summerfallow that followed corn in his wheat/corn/fallow rotation. Dietrich’s farm now uses a winter wheat/corn or milo/field pea rotation. His on-farm research and yields have shown over the past several years that his winter wheat following field peas has had similar yields to his winter wheat following fallow in his wheat/corn/fallow rotation.

Dietrich’s expected yield for winter wheat following field peas is 60 bushels. His water-use efficiencies for the winter wheat jump to 97% in this rotation.

Dietrich’s water-use efficiencies for the various cropping systems he compared were quite interesting. He compared numerous other cropping systems as well. These comparisons of water-use efficiencies help Dietrich determine which cropping rotations are best suited to maximize the amount of water he is able to harvest each year to make his operation more profitable.

I thought this was a very thought-provoking presentation. His highest water-use efficient crop was his winter wheat following field peas, which had a water-use efficiency of 97%. I visited with Dietrich after this and I’ll talk more about this topic next time.