The trials were carried out at a private farm in Plovdiv region with coordinates: 42°03’ N and 24°32’ E and 184 m on the sea level. The apple trees were planted in March 2016 at a spacing of 3,50 x 1,25 m with cvs “Golden B” and “Granny Smith”/M 26 in a North-South row orientation. Training system is spindle, irrigation system – drip and soil management natural sod mulch interrow. For the stydy were used 3 trees in 8 replicates. The trunk diameter was
measured in the beginning and the end of vegetation season and the foliar analysis - in the begining of July and August. During the season 2019 were used organic fertilizers „Keratin“ and „Lumbreco“ according BBCH stages - first treatment before BBCH 60, second - after 69 and third - one after 73 stage. The dosage of „Keratin“ was 25 kg/ha and „Lumbreco“ - one liter concentrate plus 150 liters water and from this solution 10 liter per tree. According to Gorbanov S. (2018) the optimum value of N in apple leaves is 2.6%. Near the optimal content were data from July analysis at variant „Lumbreco“ following by „Keratin“.
The optimum level of P (P2O5) is 0.4% and more of this level is for „Keratin“ only. For other macro nutrient K (K2O) the optimum content is 1.6% but the data from analysis and for
variants are very variable. More than optimal level - 0.4% of Mg were in Keratin variant and for Ca optimum - 1.5% for Lumbreco. All these data demonstrated that Keratin and
Lumbreco are suitble for organic fertilizers in apple orchards
