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Northern Prairie Wildlife Research Center

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Bird Use and Nesting in Conventional,
Minimum-tillage, and Organic Cropland

Management Implications

Minimum-tillage and organic fields in our study had a greater variety and density of birds than did conventional crop fields, particularly on fallow fields. Minimum-tillage and organic fields appeared to be more attractive to birds because more vegetation, particularly residual cover, was maintained on the land.

Although wildlife populations were higher on minimum-tillage and organic fields, success of eggs and young was low due to predation and mechanical activities. Reducing predation of eggs and young in crop fields would be difficult, but mechanical activities might be reduced in certain field types. The largest benefits of reduced nest lossed would accrue on minimum-tillage wheat and organic fallow fields because they contained the highest nest densities.

In minimum-tillage fields, hatching success might be raised by limiting spring field activities. Minimum-tillage growers are attempting to farm without tillage, but some tillage was applied on most minimum-tillage fields during our study due to weed problems. Refinements in minimum-tillage practices could result in zero-tillage systems that could increase cover on cropland and success of nesting. On organic fallow fields, destruction of nests would be reduced by delaying tillage until late June or early July. Delayed tillage of organic fallow fields could occur if growers were able to use a legume that matured later in the growing season. Later-maturing legumes could be tilled or hayed later because soil water use is delayed and forage quality is extended. Several new late-maturing legume varieties are being developed by agricultural experiment stations (J. C. Gardner, North Dakota State Univ., Carrington, N.D., pers. commun.). Field trials of later maturing legumes would be appropriate to assess the value of the practice to nesting birds and the use to farmers.

In addition to bird use in alternative farm types, we were interested in determining the effectiveness of alternative farmers in reducing soil erosion and synthetic chemical use and in maintaining crop yields. Thus, we measured soil loss on each field and estimated grain yields and synthetic chemical use by querying farm cooperators (Lokemoen and Beiser 1995).

Both minimum-tillage and organic farmers were successful in achieving respective goals of zero soil erosion or zero synthetic chemical use. However, both groups also had associated limitations because of their altered farming practices. Organic farmers reduced their synthetic chemical use to zero, but thereby reduced their grain yields, probably due to increased weed populations. The reduction in grain yields by organic farmers was partly recovered because they receive premium prices for their product. Organic farmers used more tillage to reduce problem weed growth than did minimum-tillage or conventional farmers and this procedure negatively influenced nesting and increased soil erosion.

Minimum-tillage farmers were able to maintain good crop yields with reduced tillage, but they used more synthetic chemicals compared to organic and conventional farmers. Use of synthetic chemicals is of concern because some have toxic effects on prairie wildlife (Forsyth 1989). Compared to organic and conventional farmers, minimum-tillage growers had reduced soil losses from water erosion. There also was reduced water erosion on wheat fields compared to sunflower and fallow fields, but this was true for all farm types.

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