What is the soil bulk density and how is the soil bulk density measured?

Soil bulk density is the weight of the soil in unit volume in order to destroy the natural structure, usually expressed in g/cm3. The soil bulk density reflects the soil structure, air permeability, permeability and water holding capacity. Generally, the soil bulk density of the cultivation layer is 1~1.3 g/cm3, and the deeper the soil layer is, the larger the bulk density is, which can reach 1.4~1.6 g/cm3. The smaller soil bulk density indicates better soil structure and air permeability. Orchard deep turning to improve soil, increase organic fertilizer and other measures to significantly reduce the soil bulk density.

There are many ways to determine soil bulk density, focusing on the ring cutter method:

1. Instruments: ring knife (volume 100 cm 3), balance (flux 0.1 g and 0.01 g), oven, ring knife holder, knife, small shovel, aluminum box, wire saw, dryer, etc.

2. Procedure: Select the location of the soil profile in the field first, then excavate the soil profile to observe the sun-facing aspect. Dig the soil on both sides of the pit. The depth of the excavation is generally 1 meter. If only the soil bulk density of the cultivation layer is measured, it is not necessary to dig the soil profile.

The soil profile was trimmed with a trowel, and the morphological characteristics of the profile were recorded. The samples were stratified according to profile levels, and 3 were repeated for each layer.

Place the ring knife holder on a ring knife of known weight. Paint a small amount of petrolatum on the inner wall of the ring knife. Push the ring knife edge downwards into the soil vertically until the ring is filled with the sample. If the soil is solid, you can use your handkerchief to beat slowly. The ring cutter pressure should be stable and consistent.

Cut the soil around the ring blade with a hoe, remove the ring knife that has been installed, carefully trim the excess soil on both ends of the ring knife, and clean the soil outside. At the same time in the same floor sampling with aluminum box sampling, determination of natural water content.

The ends of the ring knife containing the sample were immediately capped to prevent water evaporation. Immediately weigh (accurate to 0.01 grams) and record.

The aluminum box containing the sample was dried and weighed (accurate to 0.01 grams) and the soil moisture content was measured. Or directly remove the sample from the ring to determine the soil moisture content.

3, the result is calculated: ring knife volume is calculated as follows:

V=лr2h

Where: V - ring knife volume (cm 3);

r - radius of the knife (cm);

h - ring knife height (cm);

л - pi (3.1416).

Calculate the soil bulk density as follows:

Rs=g.100/v.(100+W)

Where: rs - soil bulk density (g/cm3);

G - Wet weight in ring knife (grams);

V - ring knife volume (cm 3);

W - sample moisture content (%).

This method allows parallel absolute error <0.03 g/cm3, taking the arithmetic mean.