Texas, USA 2010 - International Herbage Seed Group

cultivars are characterized by slender, soft and easily digestible stems. Such plant morphologyand mechanical features of the stem make them prone to lodging.Because of these characteristics, alfalfa seed yield is strongly affected by ecological factors andit varies significantly in dependence of weather conditions, more than the other crops. Averagelong-term variations in seed yield are 14,5% in corn, 17,6% in winter wheat and up to 57% inalfalfa (Zarinov & Kljuj, 1990).In regions with semi humid climate, weather conditions in the year of growing are the mainsource of variation in alfalfa seed yield. In years with high rainfall, alfalfa plants are lush andthey lodge easily. Lodged plants are not suitable for pollination and low seed yields areconsequently produced (Huyghe et al., 2001). In conditions of high soil moisture, there are noeffective cultural practices to avoid the lodging of seed crop and seed losses. The most efficientmeasure is the selection of suitable production region. Moderate soil moisture content incombination with high air temperatures is required for seed production (Goloborodko &Bodnarcuk, 1998).The objectives of this paper were to analyze the alfalfa seed yields obtained in Serbia and toestablish correlations between the seed yields and the ecological factors.Materials and MethodsImpact of weather condition on alfalfa seed yield was studied in thirteen experimental years(1997-2009) on four locations. The experimental sites were located in northern Serbia, at 45 o 83‟N, 20 o 46‟ E (Kikinda), 45 o 77‟ N, 19 o 11‟ E (Sombor), 45 o 20‟ N, 19 o 51‟ E (Novi Sad), and44°58‟N, 19°36‟E (Mitrovica). This area has a continental semi-arid to semi-humid climate, amean monthly air temperature of 11.0 o C, a total annual precipitation of around 600 mm, and ahighly uneven distribution of precipitation. Table 1 shows the monthly mean air temperaturesand monthly sums of precipitation for the period May-August.Table 1. Basic meteorological parameters of four locations in Serbia (1997-2009)ClimaticfactorMean airtemperature( o C)Precipitation(mm)Locality Month Average/May June July August TotalKikinda 17,6 21,0 22,6 22,3 20,9Sombor 17,6 20,7 22,1 22,0 20,6Novi Sad 17,7 20,8 22,3 22,2 20,7Mitrovica 17,7 20,7 22,1 22,0 20,6Average 17,7 20,8 22,3 22,1 20,7Kikinda 48,5 70,9 58,6 54,2 232,2Sombor 49,1 81,2 78,8 55,0 264,1Novi Sad 62,2 92,8 76,2 58,4 289,6Mitrovica 56,4 80,1 66,5 55,2 258,2Average 54,1 81,3 70,0 55,7 261,039