Irrigation – a Prerequisite for Sustainable Agriculture in Bulgaria | Напояването – предпоставка за устойчиво земеделие в България

Sustainable agriculture is a strategic aim of EU. One of the basic outputs of such agriculture is the achievement of a most significant and stable crop production over the years. The study is based upon statistical data relative to maize yields averaged over the country and additional yield dataset from 30 experimental fields. Experimental field data analyses indicate that yields of late hybrids cultivated without irrigation are quite unstable over the years. They are characterized with coefficient of variation Cv ranging from 30 to 60%. Lower values are relative to North Bulgaria or to the soils of high water holding capacity. Maize yields under irrigation are much more stable. Coefficients Cv are within the limits 12-18%. Average yields relative to the late maize hybrid H 708 are presented in Table 1. It is evident that yields under irrigation are about 1.7 folds those harvested in dry lands in North Bulgaria. This ratio is 2.3 in South Bulgaria. When averaging yields over the whole country territory, coefficients of variation are lower. They are from 21 to 34% over the periods 1968-1966 and 1990-2006, when the area of irrigated maize was insignificant. The coefficient of variation of yields drops to 12% in the period 1967-1989 when the irrigated area was about 30%. It is obvious that on the average for the country, irrigation used to contribute to stabilize and raise maize productivity. Figure 2 presents the averaged results about maize production sorted in a descending order. Needs of Bulgarian economy are about 1.500 000 t. It could be concluded that instead of exporting grain a substantial import is required in some years. Coefficients of variation of maize yield only from irrigated lands are within the limits 7-9% on the average over the country. Thus they are much lower compared with those relative to rainfed maize production 21-35%. If maize irrigation fields revives upon 100 000 ha in near future, the total production from irrigated and rainfed maize fields will be within the limits 1.600 000-3.100 000 t. In this way an important step towards sustainable agriculture will be maid, while the domestic need and export will be fully satisfied.