Efficiency in Potato Growing with Irrigation in Dry Climate

Improvements were introduced in technology of potato cultivation under irrigation in the conditions of the Southern Urals steppes. Key elements of agronomical complexes aimed to cultivate the crop were developed in experiments. They provide control of light regime and feeding schedule, phytosanitary characteristics of seeds to gain different levels of the expected yield. We defined water consumption regime of the crop in ontogeny for regional conditions. On the result of multivariance evaluation we defined percent of impact of the examined factors on potato crop capacity. It was set out that if water and feeding regime of soil are combined in the optimum way the potato crop makes 49 tons per 1 hectar.


Introduction
Agriculture and practice have defined the main trends of improving stability in production. They are: agricultural technology improvement, use of climatic cropping pattern, selection and others. But the only thing that may contribute to the dry areas of Russia with mean stability of guaranteed yield volume is improvement of cropland efficiency with some of its part being irrigated.
Steppe zone of South Ural is well provided with photosynthetic active radiation, but because of lack of rainfall in natural conditions of moisture it does not give high crops or yield stability, so it can not be classified as industrially developed land producing potato crops. But the need for such useful feeding stuff as potatoes is very high, so the part of irrigated land is given for this type of crops cultivated with ridge -like technology.
In this regard it becomes very important to develop the main methods aimed to get the scheduled yield volume by means of satisfying biological needs of plants.
The soil of the experimental part of the land is characterized as southern chernozem, bench type, medium-humic, with medium productivity, deeply solonized, with medium and high consentration of loam, brown and straw coloured, deposited on carbonated alluvial soil.
Hydro-physical characteristic of soil in the layer 0...1,0 m is the following: minimum water-holding capacity -23,8%, maximum hygroscopicity -8,3%, permanent wilting point -12,5% of dry land mass, density of meter long layer -1,29 t/m 3 . The experimental part of the land is plain land slightly sloped (up to 0,001) in the north-east direction. Underground water basin is 8…10 m. below. The irrigation network is of combined type. The source for the irrigated land is the water-storage basin containing 1,5...2,0 mln. m 3 of water, 95% of water comes from the river Ural, 5% is thawing water.
The experiment №1 (1999)(2000)(2001) was aimed to discover the impact that the following factors produce on the yield and tuber quality: density of planting, application rate of mineral fertilizers, cultivars of potatoes. The research work was carried out on the cultivars Karatop and Krasnopolskiy. Each experiment included 5 variants classified according to rate of fertilizer application calculated for output per hectare: control was carried out without fertilizer treatment; 30 t of tubers -N 99 P 45 K 162 ; 40 t -N 132 P 60 K 216 ; 50 t -N 165 P 75 K 270 and 60 t -N 198 P 90 K 324 . To justify the optimum density of planting the experiments were carried out with the following figures: 40, Humidity of active layer of the soil in the experiments was reserved at min 75…80% НВ level. The experiment used the split-plot method in three replications [2]. Hydro-physical characteristics of soil were defined [4 и 9], irrigation depth and consumptive water use was calculated [5]. The yield was calculated separately on each plot.
The experiments were aimed to discover energy efficiency [1], regression analysis was carried out [10] using in calculations the application program package STATGRAPHICS-2.6 (Russian version). Application rate of mineral fertilizers for the scheduled yield of potatoes was calculated as per methodology of programming station of Volgograd State Agricultural Academy, Russia.

Conclusion
Comparative valuation as per potatoes growth stage terms (seedling emergence, budding, coming into flower) showed, that in the first half of vegetation period cultivar Krasnopolskiy was in advance of cultivar Karatop (average 2…4 days in advance). But both cultivars grew fully ripe together, in 117…119 days after being planted.
Works [3], [7], [8] and other scientists discovered that photosynthesis process is strongly effected by leaf-area duration growth. Our experiments on the initial stages of potatoes growth showed that application rate of mineral fertilizers and plant population had practically no effect on leaf-area duration. But by the period of flowering all samples of variable plant population (both fertilized cultivars) showed almost twofold leaf-area growth as compared to non-fertilized. Leaf-area showed max size 57,2 thous. m 2 /ha for Krasnopolskiy cultivar and 61,2 thous. m 2 /ha for Karatop cultivar. It took place in the first decade of August in the inter-stage period: beginning of flowering-vine wilting, for samples with plant population 60 thous. units/ha.
Photosynthetic potential showed its maximum index to the end of vegetation period for cultivar Krasnopolskiy when fertilized for yield of 50 and 60 t per ha, its average index was 1,66 and 1,75 mln for the years of the research. For Karatop cultivar it showed 1,69 and 1,78 mln m 2 day/ha. Photosynthesis was most active in June at high growth of vine and in July-August at tubers' mass growth. On the fertilized irrigated fields at leaf-area extension period photosynthesis net productivity reduced from 9,5 till 8,9 g/m 2 per day for cultivar Krasnopolskiy and from 9,3 till 8,6 g/m 2 -for cultivar Karatop. Well formed leaf surface due to fertilizers and rich moisture regime contributed to improvement of tubers' daily growth for both cultivars, average by 20…46 %, and improvement of tubers' growth terms by 20 days, compared to non fertilized.
The experiment produced maximum crop capacity due to use of the fertilizers with dose rate N 165 P 75 K 270 with density of planting 60 thousand items per 1 hectar. The figures made 30.3 tons per 1 hectar for Krasnopolskiy cultivar and 46.6 tons per 1 hectar for Karatop cultivar (table 1).
Growth of application rate of mineral fertilizers and reduction of plant population provided reduction of yield for both cultivars of potatoes.
The research showed that cultivar Karatop in favorable water regime of the soil was more sensitive to fertilizers than Krasnopolskiy. Application of N 99 P 45 K 162 contributed to yield growth by 7,7…8,2 t/ha as compared to non fertilized samples. Growth for Krasnopolskiy cultivar made 3….5 t/ha.  Comparative analysis of ridge tillage time showed better figures for 30 days after planting potatoes. In this case annual weeds contamination level reduced up to one grade, for perennial weeds the same figure is 3 grades, soil density in 0…0,30 m deep by the time of yield remained 1,10 t/m 3 or within the limits optimal for tuber development. During the whole vegetation period of the crop the soil at the tuber depth had optimal temperature: from 14,4 о С in the first decade of May to 22 о С in the second decade of June. This fact had a favorable impact on the potatoes root formation, growth and development of the tops. Combination of ridge tillage time in 30 days after planting with rate of fertilizer application N 198 P 90 K 324 in this experiment produced maximum potatoes yield of the Karatop cultivar 49,3 t per 1 hа (table. 5).
Besides fertilizers impact on the potatoes yield growth was set as 92 %, the same figure for ridge tillage time was 4,2%. I.S. Shatilov [11], I.P. Kruzhilin and others [6] pointed out close relationship between the potato tuber quality and rate of mineral supply of the plant.
Really our experiments showed that growth of mineral supply contributed not only to yield improvement, but also provided tuber quality improvement. At that, average tuber mass grew (by 31…43%) and quantity of tubers per one plant also grew (average, by 9…11%).
On the average the years of research showed max tuber mass per one plant for Krasnopolskiy cultivar (715 g) with plant population 40 thousand per 1 ha when fertilized to output 50 t per hectare. Karatop cultivar showed maximum tuber mass per one plant as 780 g. with plant population 40 thousand per 1 ha when fertilized to output 60 t per hectare. The same cultivar had max tuber mass per one plant as 779 g. with plant population 60 thousand per 1 ha when fertilized to output 50 t per hectare.
Optimization of soil water regime is the essential condition to produce scheduled yield. Depending on the year of the research it took from 5 to 10 wetting with volume 200 -480 m 3 /hа to preserve humidity level min 75…80 % НВ in the active layer of the soil cultivated for potatoes. At that, irrigation need changed from 2240 tо 3250 m 3 /hа.
The achieved figures on moistness average daily flow during the vegetation period prove that they are effected by degree of soil wetting, the plant development stage and weather conditions. Maximum level of daily water requirement for potatoes (4,9…5,1 mm) was set in July-August, in the inter phase periods of budding -beginning of flowering and beginning of floweringwilting of potato tops. These periods are characterized by most rapid tops growth, maximum leaf -area and vegetation mass, as well as rapid formation and growth of potato tubers. Maximum humidity plow continued up to the third decade of August and then it reduced till 3,4…2,1 mm in the inter phase period: wilting of the tops -tuber ripening.
Potatoes need minimum of irrigation at the beginning of the vegetation period because the sprouting use water mainly from mother tuber, evaporating surface is small. Thus daily water consumption changes within limits 1,8…2,3 mm.
Increase of plant population and rate of fertilizers application result in reduction of flow intensity needed to produce one unit of the crop. Minimum water-use ratiofor potatoes was showed by samples with pant popula tion 60 thousand units/hа when N 165 P 75 К 270 was applied and made 155 m 3 /t for Krasnopolskiy and 101 -for Karatop. Combination of ridge tillage time 30 days after planting with fertilization N 198 P 90 К 324 provided further reduction of water-use ratio up to 85 m 3 /t.
Nitrate concentration in potato tubers grows after application of fertilizers in high degrees. Their use within limits of the examined measures had no negative effect on the tubers quality (table 6).
Maximum permitted level is 250 mg/kg of wet weight. Note. Average for 1999-2003. So nitrate concentration in potato tubers for Krasnopolskiy and Karatop cultivars when fertilized by N 198 P 90 K 324 made 61,53 and 60,07 mg/kg, which is 4 times less than maximum permitted level.
Energetic efficiency of the experiments was estimated by comparing figures of total energy used to produce the crops with indexes of energy received with the yield. Maximum net energetic income -56,5gigajoule /ha was produced by Karatop cultivar when fertilized by N 165 P 75 K 270 and plant population 60 thousand pants per 1 hа (table 7).  As a result, to produce 45…50 t of potatoes (Karatop cultivar) on 1 ha it is required to combine plant population of 50…55 thousand units per 1 ha with rate of application of N 165 P 75 K 270 or N 198 P 90 K 324 on 1 ha and ridge tillage time in 30 days after planting. To produce 30 t of potatoes (Krasnopolskiy cultivar) from 1 ha it is required to combine plant population of 45 thousand units per 1 ha with rate of application of N 165 P 75 K 270. Humidity in the active layer of the soil has to be kept min 75…80% НВ during the whole period of vegetation of both cultivars.