Cracking of tomato fruits in organic greenhouse trial

The objective of the research was to study how the Estonian weather conditions influence the cracking of tomato fruits of different weight and origin. Three new for Estonian conditions tomato cultivars from The Netherlands ('Auris' F₁, 'Minaret' F₁ and 'Tolstoi' F₁), two cherry type cultivars ('Gartenfreude' and 'Sun Baby') and five local widely cultivated cultivars ('Erk', 'Maike', 'Malle' F₁, 'Valve', and 'Visa' F₁) were included in the study. Four cultivars belong to the large (›90 g), four to medium (45-90 g) and two to small fruits group (‹20 g). The trial was carried out in organic conditions at Estonian Crop Research Institute in 2014 and 2015. An unheated polyethylene greenhouse was used for cultivation in soil fertilized with bovine manure at the rate of 6 kg m^-2 as the main source of fertilization. Chicken manure and seaweed solution was used three times during the growing period as additional fertilization. The number of cracked and regular fruits was counted 24 times during the vegetation period (from July to September). The weight of marketable yield and cracked fruits was determined. According to the results, it can be concluded that the percentage of cracked fruits was higher in 2014 because of higher fluctuations in daily temperatures and during the whole vegetation period. The most cracking resistant were the two small fruit cultivars and medium fruit 'Maike' showing minimal influence of the weather condition of the trial year. The cultivars 'Minaret' F₁, 'Maike', 'Valve', 'Visa' F₁, 'Sun Baby' and 'Gartenfreude' produced quite high and stabile marketable yield in unheated organic greenhouse. The yield stability of the last five cultivars was good over the both years. From the Dutch cultivars large fruited 'Minaret' F₁ had the best resistance to cracking in 2014 and medium fruited 'Tolstoi' F₁ in 2015. Both mentioned cultivars can be recommended for Estonian organic growers for cultivation in unheated greenhouses.