Abstract
The circular economy concept promotes the recycling of agricultural waste. This study was aimed at investigating the effects of cattle horn shavings on apple tree nitrogen nutrition. Ligol apple trees on P 60 rootstock were the object of the study. The experiment was conducted in the experimental orchard of the Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry, from 2015 to 2018. Two fertiliser rates were tested: 50 and 100 kg/ha N. Horn shavings (14.1% N) were applied at the end of autumn or at the beginning of vegetation in the spring and in one treatment 100 kg/ha N rate was divided into two equal parts and applied both in autumn and spring. The effects of the horn shavings were compared with the effects of ammonium nitrate (34.4% N) and the unfertilised treatment. The lowest mineral nitrogen content was found in the unfertilised orchard soil and the soil fertilised with horn shavings in the spring at 50 kg/ha N equivalent. In all other cases, the fertilisers increased the soil’s mineral nitrogen content. The lowest leaf nitrogen content was found in apple trees that grew in the unfertilised orchard soil or soil fertilised in the spring with 50 kg/ha N of horn shavings (1.58–2.13%). In other cases, leaf nitrogen content was higher (1.77–2.17%). The apple trees with the lowest leaf nitrogen content produced the smallest average yield (34.5–36.6 t/ha). The highest yield was recorded from fruit trees fertilised with 50 kg/ha N of ammonium nitrate applied in spring or horn shavings applied in autumn (42.4 and 41.4 t/ha, respectively). The influence of horn shavings on the other studied parameters was similar to that of ammonium nitrate. Horn shavings, like nitrogen fertiliser, could facilitate nitrogen nutrition management in apple trees, especially in organic orchards, where the use of synthetic fertilisers is prohibited.
Highlights
Nitrogen plays an important role in apple tree production [1], and apple tree nitrogen nutrition depends on soil and climate conditions
The lowest mineral nitrogen content was found in the unfertilised orchard soil and the soil fertilised with horn shavings in the spring at 50 kg/ha N equivalent
The lowest leaf nitrogen content was found in apple trees that grew in the unfertilised orchard soil or soil fertilised in the spring with 50 kg/ha N of horn shavings (1.58–2.13%)
Summary
Nitrogen plays an important role in apple tree production [1], and apple tree nitrogen nutrition depends on soil and climate conditions. Soil with high organic matter content, favourable weather conditions and proper soil management enhance the likelihood of adequate nitrogen nutrition in fruit trees [2,3,4]. Ammonium or nitrate fertilisers dissolve in the soil solution, and plants subsequently absorb them. They are extremely useful for the rapid correction of nitrogen deficiency in the soil. Apple trees require more nitrogen during the first half of vegetation, so spring application of ammonium nitrate is the most common practice for enhancing the fruit trees’ supply of nitrogen in conventional orchards [5]. It is difficult to predict the course of mineralisation and control the amount of mineral nitrogen released during the vegetation period [9]
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