Sod-podzolic soils have:
- acidic reaction – pH 4-5;
- exchange acidity 1-2 mg-eq/100 g, of which 80-90% is due to aluminum;
- hydrolytic acidity 3-6 mg-eq/100 g;
- cation exchange capacity 5-15 mg-eq/100 g;
- degree of saturation with bases 30-70%.
In most cases sod-podzolic soils need liming.
Agrochemical indicators depend on the granulometric composition and the state of cultivation. Sandy and sandy loam soils are characterized by low humus content to 0.5-1.0%, nitrogen – 0.003-0.08%, phosphorus – 0.03-0.6%, potassium – 0.5-1.0%, calcium, magnesium, and other macro-and micronutrients. Loamy and clayey soils contain humus 2-4%, nitrogen 0.1-0.2%, phosphorus 0.07-0.12%, potassium more than 1.5%.
Most sod-podzolic soils are poor in mobile forms of nitrogen and phosphorus, light soils are poor in potassium. At high state of cultivation acidity decreases to pH 5.1-6.0 and increases the humus content to 2.5-4.0%, labile phosphorus forms to 150-200 mg/kg, potassium to 200-300 mg/kg, the capacity of cation exchange, the degree of saturation of the bases and the provision of other nutrients.
As these soils are mainly concentrated in a zone of sufficient moisture, the use of fertilizers and liming show high efficiency. In the first minimum is more nitrogen, on poorly cultivated soils also phosphorus. On light soils, along with nitrogen-phosphorus fertilizers, the use of potassium and magnesium fertilizers is effective.
Gray forest soils
The thickness of the humus horizon, humus content and the degree of podzolization for gray forest soils can vary greatly.
In light gray soil:
- pH 4.8-5.4,
- humus content 1.6-3.4%,
- Hg and S respectively 2.3-3.8 mg-eq/100 g and 10-18 mg-eq/100 g,
- V 72-82%,
- the content of mobile forms of phosphorus and potassium in corresponds to grade 3.
Indicators are better for gray forest soils and reach a maximum for dark gray forest soils:
- pH 5.5-6.0,
- humus 3.5-7.0%,
- Hg and S respectively 2.3-5.4 mg-eq/100 g and 20-36 mg-eq/100 g,
- V 80-86%,
- provision with mobile phosphorus and potassium corresponds to grade 4.
In the first minimum on the light gray and gray forest soils is nitrogen in the second – phosphorus, in dark gray soils, the reverse sequence is possible. The need for potassium fertilizers is manifested in the cultivation of potassium-loving crops.
Depending on the level of intensification of agriculture such agrochemical indicators as pH, provision with mobile forms of elements may change towards improvement or deterioration.
Black earth soils
Black earth soils contain in the arable horizon:
- humus 4-12%,
- total nitrogen content 0.2-0.5%,
- total phosphorus 0.1-0.3%,
- total potassium reserves 2.5-3.0%,
- the reaction is from neutral for typical chernozems to slightly acidic for leached and podzoled subtypes,
- hydrolytic acidity increases from typical to leached subtypes from 0.5-3.0 to 5-7 mg-eq/100 g.
As it transitions southward from the common to the southern subtype:
- pH 7-8,
- hydrolytic acidity disappears,
- cation exchange capacity 50-60 mg-eq/100 g,
- humus content 8-12%,
- total nitrogen reserves 0.4-0.5%,
- total phosphorus reserves 0.25-0.35% in typical chernozem decreases in the transition to the northern and southern subtypes.
Provision of old, poorly fertilized or unfertilized soils with mobile forms of phosphorus and nitrogen decreases and often does not exceed grade 2-4. On such soils are effective phosphorus, and under favorable conditions of moisture nitrogen fertilizers. On the old and poorly fertilized for potassium-loving crops along with phosphorus-nitrogen fertilizers are effective potash. In the wetted areas of the western Black Earth zone fertilizer efficiency is higher, in the east depending on the aridity of the climate efficiency decreases.
In the transition from north to south, chestnut soils are divided into subtypes: from dark to light chestnut soils. At the same time their fertility decreases. Humus content decreases from 4-5 to 2-3%, total nitrogen from 0.2-0.3% to 0.10-0.15%, phosphorus from 0.1-0.2% to 0.08-0.15%, cation exchange capacity from 30-35 mg-eq/100 g to 12-15 mg-eq/100 g, slightly alkaline reaction (рНsalt) from 7.0-7.2 to 7.4-8.0, among absorbed cations – sodium specific weight increases.
Chestnut soils contain sufficiently large reserves of potassium, but have a low supply of plant-available forms of nitrogen and phosphorus. With a lack of moisture efficiency of phosphorus and nitrogen fertilizers is reduced. In rainfed conditions on chestnut soils recommend minimum doses (10-15 kg/ha) of phosphate fertilizers, which are applied during sowing. Under irrigation conditions the efficiency of nitrogen and phosphorus fertilizers increases sharply, potash fertilizers are often ineffective.
Among chestnut and especially light chestnut soils with increasing proportion of sodium in the soil absorbing complex and alkalinity reaction occurs different degrees of alkalinity. In order to increase fertility of solonetzic soils the actual and exchange alkalinity is neutralized by gypsum or acidification.
Yagodin B.A., Zhukov Y.P., Kobzarenko V.I. Agrochemistry / Edited by B.A. Yagodin. – Moscow: Kolos, 2002. – 584 p.: ill.