In a material possibilities of vlagozaryadkovy waterings are reflected, is shown as to count their norms for a charging moisture of various soils, to avoid washing away from them of nutrients and to achieve due effect in productivity of cultivated grain crops at the minimum expenses.
Vlagozaryadkovye waterings
At rational conducting irrigated agriculture the vlagozaryadka is the same important component of a mode of waterings of winter crops, as well as vegetative (spring-year waterings.
Problem of vlagozaryadny waterings is moisture accumulation in settlement layers of earth for the purpose of ensuring normal rewintering of winter crops during the autumn and winter (interirrigation) period of vegetation before the first watering in the spring.
Below, in table 1, monthly sizes of a precipitation and total evaporation are specified in the interirrigation period. A precipitation is given on the basis of mean annual these meteorological stations of the Crimea, total evaporation – from various crops measured by hydraulic soil balansomer, on available long-term series of observations.
Table 1. A precipitation and total evaporation during the interirrigation period
Apparently from the table, a precipitation for October-March, compensates total evaporation. Excess of evaporation over a precipitation is observed since April 1 and makes during the period from crops before the first vegetative watering winter (since April 20) 510 m3/hectares. For accumulation of such quantity active vlagozapasov it is necessary to humidify to the smallest moisture capacity (the top limit of optimum moistening) a layer of earth in capacity 55 see.
By researches it is established that on the low-power soils spread by calcareous shhebnistymi by deposits, winter crops it is possible to grow up not less than 0,8 m at capacity of a layer blocking limestone.
Calculation of norm of a vlagozaryadka on normalnoslozhenny polnoprofilny soils and on the low-power carbonate chernozems spread by calcareous shhebnistymi by deposits, is made on the formula deduced on the basis of long-term scientific researches:
Mvlz = 2000 – V0,7; m3/hectare (1)
where Mvlz – norm of vlagozaryadny watering, V0,7 – the general vlagozapasy in a layer of earth of 0,7 m defined by a termostatno-weight method before a vlagozaryadka (m3/hectare).
Thus, theoretically possible norm of a vlagozaryadka provided that from the specified layer of earth all are consumed productive vlagozapasy, i.e. moistening of the soil is at level of humidity of a zavyadaniye, 2000-1015=985 m3/hectares equal. However its such moistening in October yet wasn’t for all years of researches. The average norm of a vlagozaryadka fluctuates within 500-600 m3/hectares, i.e. is comparable with vegetative watering. It is quite enough this moisture to receive amicable shoots and to provide normal rewintering during the interirrigation period.
As to soils with close (less than 2,5 m) level to zaleganiye of ground waters not to cause development of processes of a secondary zasoleniye and bogging, calculation of norm of a vlagozaryadka is made in a different way.
Mvlz = NVA – Va; m3/hectare (2)
where Mvlz – norm of a vlagozaryadka; NVA – the smallest moisture capacity in a layer (and), pays off 3300´a; Va – the general vlagozapasy in a layer (and) before a vlagozaryadka.
The layer of earth which is subject to moistening at a vlagozaryadka (and), m, pays off on a formula:
and = 0,4 (N – 0,5) – 0,2; m (3)
where N – level of ground waters in day of definition vlagozapasov, m.
To calculate norm of a vlagozaryadka, despite a variety of soil climatic conditions on peninsula territories as we see, simply.
Danger of excess of norms of a vlagozaryadka consists, as it was specified above, in emergence of processes of a secondary zasoleniye and bogging on soils with a close zaleganiye of ground waters that very quickly and for a long time deduces lands from an agricultural turn. Other problem is washing of nutrients on soils with a deep zaleganiye of ground waters out of limits of an area of coverage of root system that reduces effect of application of fertilizers (first of all, nitric) since under the main processing 2/3 norms of nitrogen are brought. By researches it is established that 800 m3/hectares of the water filtered for a korneobitayemy zone carry away with themselves 65 % of mobile nitrogen. The nutrients which have left with a filtrational stream in the underlaying horizons of the soil, will be lost for plants, and it means, as the part of a crop will be lost, as well as the means spent for purchase and application of fertilizers.
Share of participation of a precipitation and irrigating water in formation of a crop of winter wheat is inadequate. Natural moistening (precipitation) forms 23 %, a vlagozaryadka – 52 %, vegetative waterings – 25 % (the first - 16 %, the second – 6 %, the third and the fourth, in the sum – 3 %) from the greatest possible crop at an optimum mode of an irrigation. It is necessary to note that a precipitation can create the specified part of a crop only provided that their norm for vegetation will be not less than 2200 m3/hectares. If it is less than precipitation, a crop on bogare can not be in general.
In table 2 data on efficiency of waterings under winter wheat are combined with costs of carrying out waterings on types of dozhdevalny cars.
Table 2. Efficiency of waterings on winter wheat
Data of researches show that one vlagozaryadka norm of 600 m3/hectares at a high agrobackground can give a grain increase, in comparison with bogary, in 30 c/hectares and frequency rate of return of expenses for watering – 6,9 times.
From the specified figures the vlagozaryadka role in receiving a crop of winter crops is visible therefore to neglect vlagozaryadkovy waterings in technology of irrigated agriculture it is impossible by no means. The similar economy of irrigating water and the financial means necessary for carrying out watering, will turn back, at the best, receiving a crop half smaller, than probably in the conditions of concrete year, and is the most real – heavy losses. The means spent for preseeding processing, seeds, crops in the autumn and, probably, on having changed in the spring of the vybrakovanny areas summer cultures, will be thrown out on a wind.
Century Lyashevsky, candidate technical sciences, M. Kudin, Candidate of Economic Sciences, A.Tishchenko, candidate of agricultural sciences, Crimean research center of Institute of hydraulic engineering and UAAN land improvement.