CROPS ADAPTATION MANAGEMENT IN THE CONDITIONS OF STEPPE LANDSCAPE OF UKRAINE

SUMMARY Preformed study approved for studied crops the dependency between crop nutrient uptake and concentration as well the impact of landscape positions, adaptation potential of species, varieties and hybrids occurrence.


INTRODUCTION
The steppe zone of Ukraine is known as a zone with intensified development of erosion processes, around 35 % of all arable lands are affected by erosion each year (Kharytonov et al. 2004). Landscape features is a major factor in erosion process. All washed soils are formed on slopes with surface runoff. The intensity of erosion processes depends on the characteristics of hill slopes including angle slope, shape, length and exposition.Intensive land cultivation, complicated relief, large share of cultivated crops in rotation promote the development of erosion processes Nazmi et al. 2011;Mehdizade et al. 2013). Excessive densifying of the upper layers of molisoils and drastic reduction in the maximal intensity of water absorption are the main causes of the progressing erosion (Stone et al. 1985;Thelemann et al. 2010). Hillslope processes are defined by unique site characteristics such as soil physical and chemical properties, water retention and flow patterns, biological processes and topographic influences (Molodovskaya et al. 2011;Marques de Silva and Silva. 2008;Rochette et al. 2011;Kaspar et al. 2003) found that in years with belowaverage rainfall, corn yield was negatively correlated with relative elevation, slope, and curvature, whereas in years with above-average rainfall, corn yield was positively correlated with relative elevation and slope.
Increasing of the adaptive capacity of crops is based on adaptation mechanisms similar to those for plants, which are representatives of natural flora (Lykholat et al. 2016). The similar data were obtained when crops growth at specific landscape positions is influenced by several interacting hill slope process across a typical soil arena (Schipanski et al. 2010;Snapp and Kravchenko, 2015;Russenes et al. 2016). Influence of landscape position and terrain attributes an annual crop yield has been studied. In particular, corn yield and total plant biomass was greater at foot slopes benefiting from more available soil water at those lower landscape positions (Stone et al. 1985;Marques de Silva and Silva. 2006).
Corn grown yield at the depositional, flat and south-western hill slope positions lower than at all other positions. There were differences in the stover to grain ratio between landscape positions. The flat landscape position had a 6.9:1 ratio of stover to grain, whereas the depositional site had a 9:1 ratio (Thelemann et al. 2010). The same tendency was established in studies showing reduced yield at lower landscapes position with excessive amounts of water tend to collect (Kravchenko and Bullock 2000;Parent et al. 2008).
Means of adaptive macro-and micro-differentiation include the ecological specialization of species and varieties sowing. The cropping plan and crop rotation has been treated using a variety of approaches based on different objectives and handled at very different scales incorporated into agronomic, economic and land-use models (Farquharson and Baldock, 2008;Lazrak et al.. 2010;Ladoni et al. 2016). As follows, the design of agroecosystems based on increasing of species, varieties and hybrid variety is the first rate task. The key element of this approach is the formation of an adaptive species structure for cultivated areas for each particular element of the natural landscape. The choice of crops and their allocation to plots is at the core of the farming system management (Negassa et al.2015;Velychko, 2014). These decisions concentrate all the complexity involved in cropping system design and selection at the farm level because of their many involvements at different stages of the crop production processes (Simic et al. 2016). The large number of possible adaptation options, model-based exploration tools are commonly used to supplement traditional empirical approaches (Schaller et al. 2012;Han et al. 2017) for designing and evaluating innovative agricultural production systems.
Allocation of ecologically similar territories and choosing appropriate crops for those should be considered as the first step. No less important task is the right choice of crops for introduction into the crop rotation for culturing on sloping lands, which characterized by different exposition.
The aim of the research is to provide an assessment of the adaptive potential of crops under the conditions of the steppe agro-landscape of the Ukrainian steppe.

MATERIALS AND METHODS
Experimental areas were divided according to rate of received solar irradiation, moisture supply, organics and mineral nutrient content in the soil (Fig. 1). Crops were planted across the main slope on the experimental field. Determination of the dependence of the plants' reaction of on the flat, northern (N) and southern (S) hill slope landscape position was planned. This approach allows to determine the areas where the same crop, variety or hybrid are grown on maximaly different reliefs, which is considered as major affecting factor. An overland gain of alfalfa, espresso, barley and corn was evaluated in the phase of agricultural maturity. The green mass of peas was sampled in the phase of branching and budding. The nitrogen and phosphorus concentration in plant samples was estimated using Kjeldahl method. Total P concentrations of the applied residues were determined by sulfuric acid digestion (Thomas et al. 1967). Potassium was determined with flame photometry.
The intensity of the nitrogen fixation of the nodules of peas was determined by the Hardy acetylene method (Hardy et al. 1968) on the gas chromatograph Chrom-5 (Czech Republic).
Crop uptake rates for nitrogen, phosphorus and potassium are calculated per yield of dry matter for crops.

RESULTS AND DISCUSSION
Calculation of release and consumption of the main nutrients by alfalfa and saffron harvests are presented in the Tables 1 and 2.
As it can be concluded from the Table 1, the rates of removal of nitrogen with aboveground biomass of alfalfa and sainfoin are higher for the hill slope of northern position. Similar effect when alfalfa biomass at the western hillslope position was higher than the depositional position (Thelemann et al. 2010).
More favorable environmental conditions also resulted in higher removal rate of phosphorus by leguminous plants on the "shadow" slope of the northern exposition (compared to the flate landscape position).
The lowest level of potassium removal was observed on the slope that was strongly eroded. In the bulk mass of the alfalfa hay, the ratio of N: P: K varied from 1:0.3:0.8 for the sample harvested from the plain land to 1:0.25:0.5 for the samples harvested on the slopes.
Obviously, these difference can be explained by the greater accumulation of nitrogen as a result of symbiosis with rizobacteria. The ratio of N: P: K for the sainfoin was virtually unchanged at rate of 1: 0.3: (0.5-0.6).
In our opinion, this can be explained by the famous fact that alfalfa, like most of mesophytes more than the sainfoin (xerophyte) had adapted to the conditions of northern hill slope position.
The data on ratio, yield and total removal of main nutritions with the biomass of two varieties of green pea at different landscape positions are shown in the table 2.
From the two mentioned local varieties of peas, "Ukisniy 9" had a lower dependence on the relief than "Lgovsky -zelenozerny".
Study of the activity of the nitrogenase complex in the root nodules of plants revealed the difference for the three varieties of peas and dependence on the landscape features (Fig. 2).
In particular, certain peas varieties local selection showed high rate of nitrogen fixation. On the northern slope, which was more humid, higher levels of nitrogen fixation (up to 200 μg of nitrogen per hour per plant) was recorded for "Vusaty" variety. The level of nitrogen fixation for peas on the plain land and at the bottom of the valley was lower than on the slopes in 2 -8 times. As it follows from the data presented in the Table 3, barley plants actively responded on the growing conditions of cultivation, which reflected on the harvest and crop nutrient removal.
The uptake of nitrogen, phosphorus and potassium with the barley harvest on the slope of the southern exposition decreased by 48 and 36 % compared to the flat landscape position.
The difference in the macronutrients concentration capacity for the aboveground mass of barley reflected on the ratio of their removal according to the elements of landscape. In particular, the ratio of N:P:K for plant harvested on the plain land was 1: 0.34: 0.74, on the slopes of the northern and southern positions, ratio changed from 1: 0.36: 0.78 to 1: 0.33: 0.76 accordingly. Table 3. Nutrients uptake rate for aboveground mass of barley and the costs required for production of 1 ton of the grain and relative quantity of leaf and steam mass of barley. The response of corn hybrids to the culturing conditions was significantly different from these observed for barley. The ratio of N: P: K, in average, for studied hybrids, was within the range of 1: 0.39: (1.01-1.07).
General features of the NPK removal with aboveground mass of corn and cost required form production of 1 ton of grain and relative leaf and stem mass for corn hybrids are presented in the Table 4 and 5. After analysis of the yield data for the corn hybrids, it should be noted the preference of the slope with the northern exposition, reflected on the bulk crop nutrient removal.
In average, the removal of N, P, K for the slope of the northern exposition was on 5.8; 2.0; 8.0 kg / ha higher than for the plain land and on 23.8; 9.2; 32.0 kg / ha higher than for the slope of the southern exposition. This observation can be explained by biological specialties of studied crop hybrids. In all environmental conditions, hybrid Dniprovsky-141 always consumed more nitrogen, phosphorus and potassium than any other studied hybrid.
CONCLUSION Preformed study approved for studied agricultural crops the dependency between crop nutrient removal and concentration as well the impact of landscape positions, adaptation potential of species, varieties and hybrids occurence. Perennial legumes (alfalfa, sainfoin) were more unpretentious. Pea varieties (Ukisniy 9" "Lgovsky -zelenozerny" and "Vusatiy") are moderately pretentious appeared to be better than cereal crops -megatrophs (barley, corn) in terms of edification for growing on slopes. It can be explained by special adaptation reactions, such as symbiotic nitrogen fixation, better capacity for absorbtion of mobile forms of nutrients from the soil, etc.