Agriculture Reference
In-Depth Information
13.1 INTRODUCTION
Wheat is one of the most important food cultures in Russia, as well as across the world.
In the agricultural zone of Tyumen region, soft spring wheat is the leading culture
among cereals. Area under cereal crop in the region increased from 616 thousand ha
in 2007 to 7,155 thousand ha in 2011. At the same time, crop area of winter wheat
decreased from 6.6 thousand ha in 2009 to 0.4 thousand ha in 2011. The productivity
of winter wheat varied within a wide range—from 9.4 centners per ha in 2007 to 36.7
centners per ha in 2011.
A limited distribution of winter wheat in the regions characterized by complicated
soil and climatic conditions has several reasons. Thus, L.V. Vikulova [1], M.V. Niko-
layev [2], and L.V. Karpova [3] noticed hard wintering conditions, the possibility of
return of frost in spring, and early spring drought events among the main limiting
factors.
A.S. Ivanenko, N.A. Ivanenko [4] noticed the necessity to develop the technology
of breeding of the given culture. The variety has a considerable importance for the
wintering and the increase of productivity [5].
It is necessary to note that the winter wheat has a set of advantages compared with
spring wheat: it withstands better the early summer drought, it uses more effectively
the moisture from summer and autumn precipitation, it suppress the growth of weeds,
and the foundation and formation of yield occur under more favorable conditions [6,
7].
It is possible to distinguish several critical periods relatively to environmental fac-
tors in the ontogenesis of a plant of winter wheat. Usually, the plants are most sensitive
to unfavorable environmental factors at the stage of seedlings and at the fi rst stages of
growth [8]. At this stage, the following limiting factors can be noted: sudden changes
of air temperature and amount of precipitation (initial stages of growth and develop-
ment of plants can occur both, under overwatering as well as under insuffi cient water
supply).
During autumn period, the formation of plant biomass and accumulation of nutri-
ents for further wintering takes place. For successful passage of the phase of third leaf,
the plants need optimal temperature regime: not above +7-12°С (especially under
insuffi cient moisture) and not below +2-3°С. In winter, the soil temperature at the
depth of the node of bushing out affects considerably the vitality of plants. Under the
temperature below −19°С, the die-back of point of increase is possible, which leads to
the death of the whole plant. The temperature decrease is especially dangerous for the
plants of winter wheat from mid-November to early December under small depth of
snow cover. The temperature oscillations (interchange of thaws and frosts) can lead to
the deformation and breach of root system of plants.
The death of plants in spring (period of vegetation resumption) may be evoked
by the return of cold weather; overwatering and hypoxia in the depressions of relief;
damage of plants by phytopathogenic fungi; and water defi cit.
Each ecological niche has its own peculiarities, which may considerably affect
the growth and development of plants. When testing the samples of winter wheat in
the northern forest-steppe of Tyumen region from 1987 to 1992, we observed that the
death of plants often falls to the spring period due to the complexity of unfavorable
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