Irrigation scheduling strategies for pepper based on evaporation and reference evapotranspiration

Abstract

The experiment with drip irrigated pepper was conducted at the Rimski Šančevi experimental field of the Institute of Field and Vegetable Crops in Novi Sad in 2019. The irrigation was scheduled on the basis of the water balance method. Two methods were used to compute the daily evapotranspiration of pepper (ETd): reference evapotranspiration (ETo) and evaporation from an open water surface (Eo). Crop coefficients (kc) and corrective coefficients (k) were used to convert ETo and Eo values into ETd. Kc and k were 0.3–0.4, 0.6–0.7, 0.9–1.1, 0.8–0.9 and 0.4, 0.7, 1.0 and 0.8 for initial stage, crop development, mid season, and late season, respectively. ETo was calculated by the Hargreaves equation. Eo values were measured by a Class-A pan located at a meteorological station near the experimental plot. Irrigation started when readily available water (RAW) in the 0.3 m soil layer was completely absorbed by plants. Differences in crop yield (Y) and irrigation water use efficiency (IWUE) obtained using Eo (42.58 t ha-1, 15.20 kg m-3) and ETo (40.78 t ha-1, 14.56 kg m-3) were not statistically different. Evapotranspiration rate was 364.2 mm and 337.3 mm in Eo and ETo variant, respectively. The fact that the differences in Y and IWUE between different calculations of ETd were not statistically significant indicates that both methods can be recommended for irrigation scheduling programs for pepper in the climatic conditions of the Vojvodina region. However, priority should be given to ETo due to the easy accessibility and reliability of data.

Navodnjavanje paprike sistemom kap po kap obavljeno je u Institutu za ratarstvo i povrtarstvo na oglednom polju Rimski Šančevi (Novi Sad) 2019. godine. Vreme zalivanja je određivano vodnim bilansom. Dve metode su korišćene za obračun dnevnog utroška vode na evapotranspiraciju paprike (ETd): referentna evapotranspiracija (ETo) i evaporacija sa slobodne vodene površine (Eo). Koeficijenti kulture (kc) i koeficijenti korekcije (k) korišćeni su za pretvaranje ETo i Eo vrednosti u ETd. Vrednosti kc i k bile su 0,3–0,4; 0,6–0.7; 0,9–1,1; 0,8–0,9 odnosno 0,4; 0,7; 1,0 i 0,8 za početak vegetacije, intenzivni porast, centralni deo vegetacije i kraj vegetacije. ETo je računata postupkom Hargrivsa (Hargreaves). Eo vrednosti su merene evaporimetrom klase A, postavljenim na meteorološkoj stanici u neposrednoj blizini ogledne parcele. Navodnjavanje je obavljano kada je lakopristupačna voda u sloju zemljišta do 30 cm bila utrošena od strane biljaka. Razlike u prinosu (Y) i produktivnosti utrošene vode navodnjavanjem (IWUE) korišćenjem Eo (42,58 t ha-1, 15,20 kg m-3) i ETo (40,78 t ha-1, 14,56 kg m-3) nisu bile statistički značajne. Vrednosti evapotranspiracije u periodu vegetacije paprike bile su 364,2 mm odnosno 337,3 mm na varijantama obračuna Eo i ETo. Činjenica da nisu utvrđene statistički značajne razlike u vrednostima Y i IWUE ukazuje da se obe metode mogu koristiti u obračunu ETd u realizaciji racionalnog zalivnog režima paprike u klimatskim uslovima Vojvodine. Međutim, prednost zbog dostupnosti podataka ipak treba dati postupku ETo.