G. Panayotova1*, S. Kostadinova2, S. Stefanova-Dobreva3, A. Muhova3
1Department of Plant production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
2Department of Agrochemistry and Soil Science, Faculty of Agronomy, Agricutural University, 4000 Plovdiv, Bulgaria
3Field Crops Institute, 6200 Chirpan, Bulgaria
(Manuscript received 6 September 2020; accepted for publication 26 February 2020)
Abstract. The aim of this study was to investigate the influence of long-term nitrogen-phosphorus fertilization and meteorological conditions during the period 1990-2019 on test weight of durum wheat grain in Central South Bulgaria. The influence of nitrogen and phosphorus rates – 0, 40, 80, 120 and 160 kg.ha-1, as well as combined NP fertilization in the same rates on durum wheat grain under conditions of stationary long-term fertilizing experiment in cotton-durum wheat crop rotation was studied. The analysis of the results showed that the test weight was below the standard requirements in eight of the studied years, and in 22 years the average test weight exceeded the requirements. The values in 17 years were over 80.0 kg. The test weight decreased by increasing the N rates above 80 kg and the lowest average value was seen at N160 – 79.4 kg. The Р application in rates from 40 tо 160 kg.ha-1 indicated a tendency to increase the test weight. Good values were realized by combining a moderate to high phosphorus rates Р80-160 with low N levels N40-80. Weather conditions during the 30-year period have a strong significant impact on the test weight of the grain.