Influence of mineral-organic fertilizers on highbush blueberry yield and quality indicators in Bulduri Horticultural Secondary School

The production of horticultural and arable crop plants is rapidly developing in the organic farming system in Latvia. Meanwhile, there is a lack of mineral-organic fertilizers in the Latvian market or they are expensive as well as not appropriate to specific crop. Besides there is a lack of knowledge about the cultivation of different crops in the organic cultivation system in Latvia. During the project “Improving the productivity and quality of organically grown crops by using of new mineral-organic fertilizers” new mineral-organic fertilizers of biological origin have been developed, including substrates for highbush blueberry. Blueberries have specific requirements for granulometric soil composition, soil reaction, and micro and macro nutrition availability. Newly formed fertilizers had been tested both in commercial farms and in Bulduri Horticultural School to evaluate whether new fertilizers provide higher yields and higher quality at the same time maintaining soil fertility and meeting the principles of sustainable farming. In the spring of 2020, the blueberry trial was established at Bulduri Horticultural School, where four different fertilizers were evaluated in three replications of four plants. Four varieties were used: ‘Patriot’, ‘Chippewa’, ‘Bluegold’ and ‘Polaris’. The fertilizers were developed by Generis, Ltd., using registered organic fertilizer GENERIS NPK 5-5-3 as a basis, which was enriched with other organic compounds. The peat substrate was supplied by Hortimed, Ltd. The conventional fertilization system was used as a control. In the trial, the number of young shoots per bush, length of shoots and number of flower clusters per bush were evaluated. In the autumn, the increase of annual shoot number in the bush, their length (cm) and yield from the bush (kg) were assessed. According to the first results obtained in 2021, the highest annual growth for all varieties was observed in the treatment where peat combined with granulated fertilizer and sapropel was used. The highest number of flower clusters was detected in control and in the treatment with peat and granulated fertilizer applied. The beginning of flowering did not differ significantly among treatments. The obtained yield varied among varieties. As regards varieties ‘Chippewa’ and ‘Bluegold’, the highest yield was harvested in the treatment where peat substrate was enriched with sapropel and plant additives.