چكيده لاتين :
Introduction: The consumption of inorganic fertilizers in agricultural ecosystems led to the destruction of
soil physical, chemical, and biological characteristics and severely affected the quality of the products.
Therefore, the application of compost fertilizers in agricultural lands has been widely considered, and it has been
mentioned as the best environmental measure. Rootstock plays a crucial role in the growth of citrus trees.
Among all the nutrients needed by citrus, nitrogen has a vital role, and a large amount of this macronutrient is
supplied in the soil every year. The release of nutrients from organic matter, especially nitrogen, is slower than
the nitrogen release from chemical fertilizers. Rootstock affects the photosynthetic capacity of the transplanted
cultivar, which is related to the annual carbohydrate redistribution and is a determining factor for vegetative
growth and reproductive development. The growth, yield and fruit quality of cultivars are, therefore, strongly
regulated by rootstock. In the recent study, the effects of compost and nitrogen fertilizers on common rootstocks
in Mazandaran province, including citrange, citrumelo, and sour orange, were investigated.
Materials and Methods: An experiment was conducted as a completely randomized design at Qaemshahr
Horticultural Research Station. The treatments included sulfur granular compost (0, 2.5, 5, and 7.5%), produced
by Mazandaran Wood and Paper Industries Company, and pure nitrogen (0, 20, 40, and 80 mg kg-1) in the form
of ammonium sulfate. Vegetative growth, including plant height, crown diameter, and the number of leaves,
were measured. Also, to study the changes in leaf nutrient concentration, leaf samples were collected, in July and
the concentration of nutrients in leaf tissue was measured. A randomized complete block design was conducted
at Qaemshahr Horticultural Research Station in 2017. The treatments included sulfur granular compost (0, 2.5, 5,
and 7.5%), produced by Mazandaran Wood and Paper Industries Company, and pure nitrogen (0, 20, 40, and 80
mg kg-1) in the form of ammonium sulfate. One-year-old seedlings of the same size from citrange, citrumelo, and
sour orange were planted in 7- kg pots containing arable soil and the treatments. The applied soil was analyzed,
and its physical and chemical properties were determined. Irrigation of all pots until reaching the field capacity
(weight method) was performed uniformly for all treatments. At the end of the growth period, vegetative growth
parameters, including plant height, crown diameter, and the number of leaves, were measured. Also, to study the
changes in leaf nutrient concentration, fully developed leaves samples were collected, in July and the
concentration of nutrients was analyzed. Nitrogen was determined by the Kjeldahl method with a sulfuric acidhydrogen
peroxide mixture. Phosphorus by calorimetric, potassium using a flame photometer, and calcium,
magnesium, iron, manganese, zinc, and copper were measured using the flame atomic absorption method.
Results and Discussion: Results showed that the highest nitrogen concentrations in citrange and citrumelo
seedlings were 2.92 and 2.97% due to 40 and 80 mg kg-1 N and 2.5% compost, respectively. In citrumelo
rootstock, plant height increased with enhancing nitrogen application levels at different compost levels. Compost
levels did not show a significant increase in citrange height, but the highest height growth was observed at 40
and 80 mg kg-1 nitrogen. In the sour orange rootstock, consumption of high levels of compost and nitrogen
significantly reduced plant height. In all three rootstocks, the highest concentrations of potassium were observed
in high levels of compost and no nitrogen application. The concentration of iron and zinc in citrumelo leaves
increased with increasing compost levels. The trend was different in citrumelo so that consumption of 2.5%
compost and 40 mg nitrogen fertilizer showed the highest concentration of leaf iron (151 μg g-1), while the
application of 5% compost without nitrogen reduced the concentration of iron to 62.2 μg g-1. Changes in citrange
zinc concentration were similar to citrumelo. In sour orange, iron concentration changed limitedly and ranged
from 83.8 μg g-1 in 2.5% compost and 20 mg kg-1 nitrogen fertilizer to 61 μg g-1 in control. In this rootstock, the highest concentration of zinc was obtained from no compost application and 40 mg kg-1 nitrogen (28.14 μg g-1),
whereas the lowest concentration of iron was observed in control. Citrange seedlings performed better in nutrient
uptake than citrumelo and sour orange seedlings. Consumption of 5 and 7.5% levels of compost in sour orange
rootstock reduced plant height and crown diameter and caused rosette, led to an increase in the number of leaves.
The most effective level of nitrogen in sour oranges was 80 mg kg-1 nitrogen. Application of 80 mg kg-1 nitrogen
and 2.5% compost, and 80 mg kg-1 nitrogen and 5% compost led to the highest number of leaves in citrumelo
and citrange rootstocks, respectively.
Conclusion: According to vegetative growth and concentration of nutrients data, especially from the nitrogen
concentration point of view, maximum vegetative growth was obtained in citrumelo rootstock from 2.5%
compost and 40 mg kg-1 nitroge.
