Rogozhina Ye. V.
All Russia Scientific and Research Institute of
Floriculture and Subtropical Crops, Sochi, Russia, e-mail: RogojinaEW@yandex.ru
Influence of fertilizers on nitrogen-fixing
activity of brown forest acid soil in a tea plantation of subtropical Russia
We studied the potential
nitrogen-fixing activity of brown forest acid soils of tea plantation under the
influence of fertilizers in the conditions of the Black Sea coast of Russia. In
general, nitrogen-fixing activity (AA) of soils was characterized by low values
and ranged from 0.37 to 2.1 ng C2H4 / (g h). Adding
fertilizers in medium (N200P60K50 kg / ha of active substance) and the highest
(N600P180K150 kg / ha of active substance) doses inhibited the nitrogen-fixing
ability of brown forest acid soil of tea plantation.
Keywords: tea plant, the potential
nitrogen-fixing activity, fertilizers, subtropical zone of Russia.
Brown forest acidic soil of moist
subtropics of Russia of natural biocenoses (beech and hornbeam forest) are
characterized by low supply of available forms of nitrogen (30 - 50 mg/kg) [5],
so the cultivation of agriculture, especially tea (Camellia sinensis), requires
the use of high doses of nitrogen fertilizers.
One of the criteria used for monitoring
the microbial succession in the soil under the influence of fertilizers and
determination of the level of agrogenic load is the study of the intensity of
the nitrogen fixation process. The process of nitrogen fixation is influenced
by a complex of various factors: acidity, humidity, soil temperature, the
presence of mobile forms of nitrogen, the composition of the microbial
community and the relationship of microorganisms, fertilizers. As a result,
nitrogen-fixing capacity of soils varies depending on the vegetation period
plants, agrocenosis, agricultural practices of cultivation [8]. In experiments
of in vitro has been long ago established the influence of inhibition of
nitrogen fixation in the presence of free forms of nitrogen in the environment,
but the question of its impact on nitrogen fixation in the soil in the presence
of the plants is still complex and poorly studied [7].
In this regard, the aim of this study
was to explore the features of the effect of different doses of fertilizers on nitrogen-fixing
ability of potential brown forest acid soil in the conditions of agro-ecosystems
of tea in subtropical zone of Russia.
We studied the nitrogen-fixing activity (AA) of brown forest acidic soils of beech and hornbeam
forests (background) and three varieties of the
experimental sections of many years tea plantation of Kolkhida sort the coastal
strip of the Big Sochi (Uch-Dere). Exploring options differed
in doses of applied mineral fertilizers: control - N0P0K0
(without fertilizers); single - doses
N200P60K50 kg / ha of active substance; triple
doses - N600P180K150 kg / ha of active substance. The
size of experimental plots - 50m2. Fertilizers by the experimental
scheme were brought in according to the zonal Guidelines: 60% of nitrogen and 100% of phosphate and potash fertilizers in April,
40% of nitrogen - in June, in the form of dressing. The mixed soil
samples were taken in August and October 2008, from the topsoil (0 -10cm) in compliance with the rules of sterility.
Potential nitrogen
fixation was determined by the method of acetylene reduction on a Kristall-2000
gas chromatograph with flame ionization detector and a column length of 1 m,
column diameter of 3 mm, filling of Porapak N 80/100, column temperature of
60°C, detector temperature of 160°C, vaporizer temperature of 100°C, carrier
gas flow (N2) of 50 ml/min, air flow of 280 ml/min, and hydrogen
flow of 28 ml/min. The activity of nitrogen fixation was expressed in ng of C2H4/(g
h) [6]. Agrochemical characteristics were determined by methods widely used in
the practice of agrochemical analysis [1]: pHsal was determined
potentiometrically in a suspension with a soil : KCl solution ratio of 1 : 2.5
(ionometer pH-121); the humus content was determined according to the method of
Turin in the modification of Orlov and Grindel’; the content of mobile forms of
phosphor and potassium it was determined according to Oniani; easily hydrolyzed
nitrogen was determined according to Turin and Kononova using the colorimetric
method with the Nessler reagent, colorimeter KFK-3 (wave length 400–440 nm);
and humidity was determined by the weight method.
The temperature of air and soil in
August - +240C and +180C, in October - +170C and +130C,
respectively. Soil moisture during this period varied slightly (August
average of 36.5%, in October - 34.8%), which was due to sufficient rainfall in August. The acidity of the
samples varied in the range of 3.06 to 4.2 (Fig. 1).
Fig.1. The acidity of the soil
experimental tea plantation
According to the established gradations, these soils were characterized
by low (N0P0K0, N200P60K50) and medium (forest, N600P180K150) humus content (average of 3.3 and 5.5%, respectively); hydrolysable nitrogen content varied from low values (forest, N0P0K0)
to high (N600P180K150) (from 53 to 187 mg/kg,
respectively); provision of mobile phosphorus - from low
(N0P0K0) to high (N600P180K150) (from 108 to 1200 mg/kg,
respectively); potassium content is high (from 464 to
478 (mg/kg) [4].
The studies found that the of brown
forest acidic soils of beech and hornbeam
forests (background) in the summer-autumn
period were characterized by low values of the potential nitrogen-fixing
activity(AA) (Fig. 2) and were
comparable with the values obtained for the brown earth of the southern taiga
forests(pHH2O= 4.6) [2]. This fact was due to
the high acidity of the soil solution which inhibits the nitrogenase activity of
free nitrogen fixers [3; 7].
AA soil agrophytocenosis of tea (without fertilizer) had values close to the background. Adding fertilizers in medium (N200P60K50), and in high doses
(N600P180K150) inhibited the nitrogen-fixing ability of brown forest acid soil of
tea plantation (Fig. 2).
Fig.
2 Potential nitrogen-fixing activity (AA) influence of
fertilizers in a tea plantation
The decrease in the AA control values (N0P0K0) under the
influence of the fertilizer is more pronounced in October (2.4 times) compared to August (1.3 times). This correlated with the acidity (Fig. 1) that we have previously noted
(r = - 0.74) [8].
With the reduction the acidity of the soil in October, the decrease of AA during the fall was determined,
apparently, by the soil temperature, to a lesser extent by humidity.
Thus, minor differences of nitrogen-fixing capacity of the soils
of natural cenosis (beech and hornbeam forest) and agrocenosis of tea
plantation (without mineral fertilizers) were set at this stage. The application of mineral fertilizers in the studied doses inhibited
the nitrogen-fixing ability of brown forest acid soil of tea plantation.
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