Austrian winter peas as a cover crop in a wheat-sorghum rotation

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Austrian winter peas have a growth pattern very similar to that of winter wheat. It is established in the fall, overwinters, and makes some additional spring growth. As a cover crop, it is then terminated sometime in the spring prior to planting of a summer row crop.

There are several potential benefits of planting Austrian winter peas as a cover crop:

• As a legume, it provides supplemental nitrogen to the soil
• Reduced erosion potential
• Captures left-over nitrogen from the previous crop
• Provides habitat for soil-improving microorganisms

However, cover crops can also use up soil moisture that would otherwise be available to the cash crop, potentially reducing yields. It also adds an extra expense to the cropping operation.

A no-till research project was conducted from 1996 to 2008 by Bill Heer, former agronomist-in-charge at the South Central Kansas Experiment Field near Hutchinson, to evaluate the effects of winter peas and their ability to supply nitrogen to the succeeding grain sorghum crop.

Methods

Within a no-till wheat-grain sorghum rotation, winter peas were planted in the fall after wheat harvest. Half the plots were not planted to the cover crop. Where winter peas were planted, they were chemically terminated at two different times – April and May. The plots, both where the cover crop had been grown and without a cover crop, were then fertilized with nitrogen broadcast at the rates of 0, 30, 60, and 90 pounds per acre. The plots were then planted to grain sorghum. Phosphate was applied at the rate of 40 lbs/acre in the row when planting grain sorghum and wheat.

Winter peas were planted at the rate of 40 lbs/acre in 10-inch rows with a double-disc drill.

Results

Each component in the rotation was present every third year. Grain sorghum was harvested in 1996, 1999, 2002, 2005, and 2008. Yields are summarized in the chart below, averaged over all five years.

 

 

Grain sorghum yield as affected by N rate, winter pea cover crop, and termination date: South Central Kansas Experiment Field 1996-2008
Cover crop treatment	Cover crop termination date	N rate (lbs/acre)	Yield, 5-year average (bu/acre)
None	N/A	0	62.0
		30	79.1
		60	84.2
		90	98.2
		Average:	80.9
Winter peas	April	0	84.9
		30	90.8
		60	92.5
		90	85.2
		Average:	88.4
	May	0	84.3
		30	89.7
		60	92.2
		90	95.0
		Average:	90.3

 

Conclusions

• Averaged over 5 years and all N rates, Austrian winter peas as a cover crop increased grain sorghum yields by about 7-9 bu/acre.
• Termination date of the winter peas made no significant difference in sorghum yield.
• Where nitrogen was applied at the highest rate, 90 lbs/acre, the beneficial effect of winter peas on sorghum yield disappeared. In fact, sorghum yields were highest where N rates were 90 lbs/acre and no cover crops were grown. At all other N rates, winter peas improved sorghum yields.

For more details, see Austrian Winter Pea: Effects on N Rates and Grain Sorghum Yield in a Cover Crop, Grain Sorghum, Winter Wheat Rotation, Keeping Up With Research SRL 142: http://www.ksre.ksu.edu/bookstore/pubs/SRL142.pdf

 

DeAnn Presley, Soil Management Specialist
deann@ksu.edu

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