Organic Production of Cash Cereals and Pseudocereals - Organic Agriculture Towards Sustainability - page 229

root- or oil seed crops. In exceptional cases, cereals can be grown for two consecutive years,
for example a winter and summer cereal. In that case, it is best to use a less demanding crop
(rye or oat in cool climates, maize or millet in warmer climates) as the second crop. Compared
to conventional rotations, organic crop rotations generally have a lower proportion of cereals,
not exceeding 50%. Above this rate, only crops with low nutrient demands (rye, oat, triticale)
can be used. If a legume such as red clover or alfalfa is used as foregoing crop, phytotoxicity
od the decomposing residues may be a problem for the germinating seeds of cereal crops [6].
Therefore these foregoing crops should be ploughed under at least three weeks before the
cereal is sown.

Because the maize is more demanding for N than temperate cereals, maize is usually grown
after a leguminous green manure or fodder crop [7]. Maize is often only rotated with soybeans
in conventional production systems, but a corn-soybean rotation does not provide adequate
N in an organic system, as most of the N is removed with the soybean. Thus, organic rotations
need to include additional leguminous crops besides soybeans or use additional animal
manure. A common organic rotation used in the Midwestern USA consists of maize, soybeans,
a cereal, legume green manure, and a fifth crop that is varied from year to year [8]. The effects
of 2- versus 4-year rotations on corn and soybean yields were studied in organic and conven‐
tional systems in Minnesota [9]. Maize in the organic four-year maize-soybean-oat/alfalfa-
alfalfa rotation yielded only 7-9% less than in the conventional two-year rotation, and almost
twice the yield in the organic 2-year rotation. In another study in Iowa, yields of organic and
conventional corn were equivalent in a similar 4-year rotation [10].

Cereal crops also have a useful function for the following crops in an organic rotation, due to
their fibrous root systems that may loosen deeper soil layers, depending on the particular crop
(Table 1). Moreover, monocotyledonous crops generally are not susceptible to diseases of
dicotyledonous crops and, thus, provide a break in the build-up of diseases of dicotyledonous
crops.

Root Pertinence

like cover
crop

Tolerance to
yourself

Foregoing crop
quality (generally)

Crop Land coverage

Amount Depth

Winter wheat + ++ + + + +++

Spring wheat + + + - + ++

Winter rye ++ ++ ++ ++ ++ ++

Winter barley + + + +++ + +++

Spring barley + + ++ ++ + ++

Oat ++ ++ ++ - + ++

Millet ++ +++ + - + ++

Explanatory notes: +++ good; ++ proper; + poor; - improper

Table 1. Properties of cereals when used as a foregoing crop (arranged according to Demo, Bielek et al . [11].