Microbial fertilizer increase nitrogon uptake and fruit yield of apple trees infected with Baikal disease

ObjectivesThis paper studied the effects of microbial fertilizer on alleviating the Baikal disease and growth, nitrogen uptake, yield and quality of apple plant.

MethodsTaking the seedlings of the five-year-old ‘Yanfu 3’/M26/Malus hupehensis Rehd. as tested material, a two-years’ field trial was conducted using ¹⁵N trace technique. Three treatments were designed: sick apple tree (infected with Baikal disease) applied with chemical fertilizer (CK), healthy tree applied with chemical fertilizer (T1) and sick tree applied with both microbial and chemical fertilizer (T2). A hundred of fruits were randomly picked up from each treatment at fruit ripening period. The whole trees were cut down as samples, and the absorption and utilization of the ¹⁵N were determined.

Results1) The root biomass and new shoot length of apple trees in T2 were significantly higher than those in CK and T1. The dry biomass of fine roots and thick roots, the branch length in T2 were 39.4%, 157.0% and 42.0% higher than in CK, respectively. The Ndff values in CK and T2 were significantly lower than those in T1 in all the tested organs. The Ndff of fruit, new shoot, leaf, fine root, thick root, perennial shoot and trunk in T2 were increased by 93.4%, 75.6%, 63.7%, 96.1%, 80.2%, 103.4% and 95.0%, compared to those of CK. The ¹⁵N utilization rate of T2 treatment was 14.4%, significantly higher than those of T1 treatment (10.4%) and CK (6.7%). The ¹⁵N partitioning rates in the leaf, fruit and new shoot in T2 treatment were all significantly higher than those of CK and T1 treatment. The disease control effect of microbial fertilizer (T2) was only 7.1% in the first year, and increased significantly to 20.9% in the second year. In the second year of T2, the individual tree fruit yield was 6.3 kg, single fruit weight was 208.2 g, soluble sugar content was 14.3%, titratable acid was 0.5% and the sugar acid ratio was 27.6, which were significantly higher than those in CK, but still not as high as in T1.

ConclusionsMicrobial fertilizer can promote the root growth of apple plant infected with baikal disease, enhance the uptake and transport of nitrogen, and alleviate the effects of baikal disease on yield and quality of apple to a certain extent.