6 Aleksandra Głowacka
This is why other cereals, such as wheat or oats, are introduced in strip
cropping, in order to limit the negative effect of maize on the accompanying
plant (Iragavarapu and Randall 1996). Next to the soy, the common bean is
often introduced for strip intercropping because it is a legume commonly
grown for consumption in different regions of the world. In the study
conducted by Głowacka (2013b), common bean seed yield was on average
13% higher in common bean/dent maize/spring barley strip cropping than in
sole cropping. Strip cropping also significantly increased the number of pods
and seeds per plant of bean, seed weight per plant and 1,000-seed weight. It is
significant that the beneficial effect of strip cropping on the yield of the
common bean was particularly pronounced in plots where mechanical weed
control was used. This was probably due to the smaller weed infestation
observed in the common bean crop on the plots with strip cropping and
mechanical weed control (Głowacka 2013a). Furthermore, the adjacent maize
strip formed a barrier protecting the bean plants from the wind, which may
have improved water utilization and the temperature in the bean crop, thus
favourably influencing the number of pods per plant. It was also showed that
seed yield and elements of the yield structure varied depending on the position
of the row in the bean strip. The lowest number of pods and seeds per plant
were in the row adjacent to spring barley, and the highest number in the row
adjacent to maize. But the highest seed weight per plant was noted in the row
next to barley. In the row directly adjacent to maize, a pronounced negative
effect of the maize was observed and the bean seed yield was lowest, but in
successive rows the yield increased and was highest in the row next to spring
barley. The maize and beans were sown at the same time, and maize has slow
initial growth. During the seed-filling period, the competitiveness of maize
with respect to bean was higher, so the seed weight per plant was higher in the
row directly adjacent to barley (Głowacka 2013b).
Research on strip cropping has generally found an increase in the yield of
cereals accompanying maize and soybean (Ghaffarzadeh et al., 1994,
Iragavarapu and Randall 1996). According to Głowacka (2013b), the yield of
the spring barley in the common bean/dent maize/spring barley strip cropping
was 4.9% higher than in the sole cropping. The barley was sown 3-4 weeks
earlier than the other plants, so there was less competition in the edge rows
during the early developmental phases. In the later period, when the bean and
maize plants could compete with the barley, it needed less water, nutrients and
light. According to Fukai and Trenbath ( 1993 ), avoiding the overlapping of
critical periods improves complementarities in the use of resources between
intercrop components with positive implications on resource-use efficiency.