According to many investigations in Bulgaria and abroad irrigation with reduced irrigation depths causes no proportional decrease in crop yield. The water-use efficiency from rainfalls and water applications is greater at smaller depths than at the optimum ones, especially in soils with great water-holding and good capillary properties. This information is worth for farmers from regions with insuffi cient and variable rainfalls and from countries under hard economic conditions. The main problem is how to obtain maximum production of good quality and of high probability rate to meet the food demand of the population. The paper presents an investigation of the dynamics of the available for plants water content at irrigation and rainfed conditions within the profile of a cinnamonic red forest soil during the vegetation period of two earthed-up crops – maize and soybean. The soil type is widely spread over the irrigated territories in South Bulgaria and the two crops have strategic share in the grainforage balance in Bulgaria. Th ey are very responsive to water in the process of yield formation. The yields obtained at different available water probability are well founded and the allowable soil water deficit, considering some economic criteria for each crop, is determined. Some conclusions about irrigation of the two crops in water deficit conditions and practical advises are derived. The work is developed on the base of long-term field experiments in the region of Sofia, Bulgaria.

cinnamonic red forest soil; water deficit; available water; irrigation; yield; Bulgaria

Published by University of Zagreb, Faculty of Agriculture, Zagreb, CROATIA
Sponsored by Ministry Science and Education of the Republic of Croatia