Yield and evapotranspiration of forage sorghum depending on preirrigation soil moisture

Abstract

A two-year study on the effect of irrigation on the green forage yield and evapotranspiration of forage sorghum has been conducted at Rimski Šančevi experiment field of Institute of Field and Vegetable Crops on the calcareous chernozem soil on the loess terrace. The study included irrigation variants with pre-irrigation soil moistures of 60-65, 70-75 i 75-80% of field water capacity (FWC) and the non-irrigated control. The effect of irrigation on forage sorghum yield was statistically significant. The average yield increases due to irrigation practice were from 30.6 to 45.5%. The highest yield of forage sorghum was achieved in the variant with pre-irrigation soil moisture 70-75% of FWC (95.74 t ha'1). That value represents the technical minimum (TM), or the lower limit of optimum soil moisture for forage sorghum in the soil with medium and heavy mechanical composition. Evapotranspiration of forage sorghum was determined on the basis of a balancing of water consumption from the soil reserve (2 m depth), the rainfall during growing period and irrigation requirement. Water consumption for evapotranspiration of forage sorghum ranged from 571.4 mm to 629-6 mm in the irrigated variants and from 428.9 mm to 472.9 mm in the control. Water consumption for evapotranspiration in the irrigation variant with the highest yield of forage sorghum (pre-irrigation soil moisture 70-75% of FWC) ranged from 576.2 to 630.9 mm, or 603-9 mm on the average. It can be concluded that the forage sorghum water requirement is at the level of 600 mm in the climatic conditions of the Vojvodina Province.

U ogledu, u poljskim uslovima, ispitivan je efekat različite predzalivne vlažnosti zemljišta na prinos zelene mase krmnog sirka. Takođe, utvrđene su potrebe ove biljne vrste za vodom, odnosno potencijalna evapotranspiracija (ETP). Ogled je izveden na Oglednom polju Naučnog instituta za ratarstvo i povrtarstvo na Rimskim Šančevima na zemljištu tipa karbonatni černozem lesne terase. Ogled je postavljen po metodu blok sistema i prilagođen uslovima navodnjavanja kišenjem. U ogledu su bile zastupljene varijante navodnjavanja sa predzalivnom vlažnošću zemljišta 60-65, 70-75 i 75-80% od poljskog vodnog kapaciteta (PVK), kao i kontrolna varijanta bez navodnjavanja. Vreme zalivanja odredivano je praćenjem dinamike vlažnosti zemljišta termogravimetrijskom metodom. ETP za pojedine otkose i vegetacioni period krmnog sirka određen je bilansiranjem potrošnje vode iz rezervi zemljišta padavina i norme navodnjavanja. Na varijanti navodnjavanja sa predzalivnom vlažnošću zemljišta 70-75% od PVK postignut je najveći prinos zelene mase (95,74 t ha"1) i te vrednosti vlažnosti zemljišta predstavljaju predzalivnu vlažnost, odnosno tehnički minimum vlažnosti za krmni sirak na srednje lakim do srednje teškim zemljištima po mehaničkom sastavu. Potrebe za vodom (ETP) krmnog sirka u klimatskim uslovima Vojvodine iznose oko 600 mm.