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Effect of Nitrogen Fertilization in the Sour Cherry Orchard on Soil Enzymatic Activities, Microbial Population, and Fruit Quality
Sour cherry (Prunus cerasus L.) is one of the most important fruit crops in Poland and ‘Łutówka’ is the dominant cultivar in commercial orchards. The experiment was carried out in 2007–2013 in three orchards; in each of them, three levels of fertilization were applied: 0 N kg ha−1, 60 kg N ha−1, and 120 kg N ha−1. The activity of dehydrogenase and protease in the soil was studied depending on nitrogen fertilization. The abundance of soil microorganisms was assessed: bacteria, fungi, actinomycetes, and nitrogenous bacteria (Azospirillum and Azotobacter) in the years during the experiments carried out with fertilization of 60 kg N ha−1 in all orchards. The enzyme activity of dehydrogenases increased after the use of 60 kg N ha−1 from 3.8 to 6.7 (cm3 H2 24 h−1 kg−1 DW soil), but a further increase in the dose to 120 kg N ha−1 caused a decrease in activity to 5.1 (cm3 H2 24 h−1 kg−1 DW soil). The activity of proteases was dependent on nitrogen fertilization, but to a large extent it was related to the course of climatic conditions. There is no relationship between the growth and the activity of proteases. The yield and selected quality parameters of the cherry fruits were associated with both dehydrogenases and proteases. The use of lower doses of nitrogen fertilizers allows for maintaining biological balance in the soil and a more efficient use of nutrients, contributing to less environmental pollution.
Effect of orchard site and climatic conditions on plant nematode density levels
Phytoparasitic nematodes are commonly found in the soil and their presence can lead to plant diseases, weaker growth, reduced yields and lower fruit quality. A study conducted in 2006–2009, involving the monitoring of climatic conditions, identified the influence of precipitation and temperature on the number of nematodes, in 7 sites within a cherry orchard. Soil samples to assess nematode populations were taken from 7 sites that differed in terms of cultivation and age: 5 cherry orchards established in different years. Not all nematode taxa responded in the same way to temperature increase. Members of the families Belonolaimidae, Trichodoridae and the genus Aphelenchus increased in number with rising temperatures. The negative water balance limited the number of nematodes in the soil in the layer up to 30 cm, whereas the increase in soil moisture had a positive effect on the development of Paratylenchus spp., and mebers of the family Hoplolaimidae and Heterodera. The largest total number of nematodes was found on the strip cultivated with agricultural crops after orchard liquidation. However, parasitic nematodes accounted for were at low levels (17%). The size of fruits from trees growing on sites with a large number of nematodes decreased with a simultaneous increase in total soluble solids and fruit firmness.