The dynamics of soil fertility of arable lands in Goshcha district of Rivne region

Abstract

Topicality. According to agrochemical researches and field experiments of scientific institutions, the change of maintenance of humus, nutrients and reaction of soil solution that leads to agrochemical degradation is observed due to high-intensity uses of land resources, scientifically unreasonable system of agriculture.

Objective - study of dynamics of soils’ fertility indexes of arable lands of Goshcha district of Rivne region is based on the results of the last 5 rounds of agrochemical certification of agricultural lands (1996-2016).

Methods: analytical, method of comparison and calculation, and statistical. Complex agrochemical assessment of soils was carried out on a 100-mark scale in comparison with reference indicators.

Results. During the researches it is identified that during the years 2001-2016, the content of humus in 0-20 cm layer of soil of arable lands is distinguished by a constant tendency to descend generally in the area.

In the ninth round the change of the weighted average indicator was recorded for 8,9%, i.e. the decrease from 2,58 to 2,35%. The tendency to descend in the weighted average indicator remained in the tenth and eleventh round. In the eleventh tour the weighted average indicator was 2,26% that is 12,4% lower than the weighted average indicator in the eighth round.

According to the results of the seventh round (1996) of agrochemical inspection of arable lands in the area, there were 13,4% of soils with acidic reaction of soil solution (рН_KCℓ less than 5,5), with weighted average рН_KCℓ indicator of 6,3.

The increase in acidity and decrease in the weighted average indicator of рН_KCℓ is traced till the tenth round. For 2011 рН_KCℓ reached its minimum and constituted 6,0. The areas of acid soils were 29,3%.

According to the results of the XI round of agrochemical certification, the ascend of the weighted average indicator of рН_KCℓ on 0,3 units and the descend of the areas of acid soils up to 17,9% is remarked.

Content of nitrogen, that is easily hydrolysed during 1996-2001 was decreased from 120,0 to 81,0 mg/kg of soil, or by 32,5%. During the following five years there was seen an increase in the contents of nitrogen to 89,0 mg/kg of soil, or for 9,9%.

For 2011 the content of nitrogen increased to 136,0 mg/kg of soil, or for 52,8% to the previous round. In XI round of examination, the reduction of content of nitrogen by 9,6% was observed, and therefore the weighted average indicator was 123,0 mg/kg of soil. In the same round , the increase by 2,2 times of the areas of soils with extremely low content of nitrogen, and for 5,7% with low content of nitrogen and the reduction of the areas with an average (by 2,2 times) and elevated content of nitrogen (for 45,0%) are traced.

According to the results of VII – IX rounds of agrochemical examination, the gradual decrease in content of labile phosphorus from 162 to 152 mg/kg of soil was established.

According to dynamics of content of labile phosphorus there was a redistribution of the areas on this indicator: during VII-IX rounds increase in the areas with extremely low, low and average content of labile phosphorus (for 30,0%) and reduction with very high content of it (for 31,5%) was observed.

In the tenth round in 2011, the growth of the contents of phosphorus in soils of the area is traced: the weighted average indicator grew by 24 mg/kg, or 15,8%, and constituted 176 mg/kg of soil. Owing to the essential growth of the contents of labile phosphorus in soils, the dynamics of distribution of the areas according to its contents received the opposite character.

Hence, the increase in the areas with very high content of phosphorus in 2,6 times and the reduction with extremely low, low and average on 44,4 is established; 40,0 and 25,6% respectively.

The tendency of gradual decrease in content of labile phosphorus was indicated in the eleventh round. The weighted average indicator is 167 mg/kg of soil, that is 5,1% lower than in the previous tour. During the last five years the number of introduction of Р₂О₅was reduced to 14 contrary to 26 kg/ha on average for 2006-2010.

Dynamics of providing the soils of arable lands of the area with exchange potassium was similar to dynamics of providing with labile phosphorus and significantly depended on volumes of introduction of potash fertilizers.

During VII-IX rounds of agrochemical examination of soils of village councils on providing soils with exchange potassium, it is established the descending dynamics of its contents, in particular the decrease in the average indicator from 103 to 87 mg/kg of soil, or on 16 mg/kg of soil.

During the research a tendency in growth of the contents of exchange potassium from IX to X round of examination was revealed. So, at the beginning of 2011 the growth of the average indicator of contents of К₂О from 87 to 132 mg/kg of soil, or on 45 mg/kg is traced in the area (by 1,6 times). Changes in contents in the soil of К₂О determined redistribution of the areas according to the level of provision. During IX-X rounds of examination in the area, the increase in a share of soils (% of examined) with the increased content from 12,7 to 27,0%, with high - from 4,5 to 22,4% and extremely high - from 0,1 to 3,4% and reduction of a share of soils with very low contents - from 8,7 to 2,7% and low - from 44,2 to 20,5 was discovered.

In XI round of examination of soils of the area, stabilization of the average indicator of content of К₂О at the level of 130 mg/kg of soil was recorded.

According to the results of complex agrochemical assessment from VIII to XI round of examination in the area, reduction of level of the complex agrochemical point (CAP) with 50,5 to 48,5 is recorded.

In the tenth tour the increase in the level of tillage of the soil of arable lands to 58,9 with fluctuation within 33,4-72,3 is recorded.

During XI round of agrochemical examination of soils, insignificant reduction of CAP to 58,5 is discovered and fluctuation of CAP within 33,1-65,8 that demonstrate decrease in some indicators of their fertility is clarified.

Prospects. The usage of complex agrochemical point as a complex assessment of evolution of fertility of soils of Goshcha district may form a basis for local programmes of increase in fertility of soils on the short-term perspective that will provide soils of the region with constant high crops.