Methodology and advantages of vegetation-microfield experiments in agrochemical research

The vegetation-microfield method: how to bring experiments closer to the actual field

Standard vegetation experiments in greenhouses poorly reflect how fertilizers or products will perform in the field. In enclosed spaces, temperature regimes are far from natural, and irrigation is regulated artificially. The vegetation-microfield method solves this problem: plants develop in the zone’s real climate and can utilize moisture from subsoil horizons.

Bottomless vessels are used for the experiment; they are buried flush with the ground and filled with the soil under study. Alternatively, a trench can be dug, its walls isolated with polyethylene film, and divided by transverse partitions into individual sections. Pre-sowing irrigation is performed during setup, and subsequent water supply is provided by precipitation and groundwater, unless the experimental design includes the study of irrigation regimes.

• Depth of bottomless vessels — 50–60 cm
• Minimum monolith depth — 60 cm
• Maximum monolith depth — up to 3 m

The method is indispensable when studying soil microflora and pests. For example, when soil is infested with cereal root rot, gray mold of sunflower, or cotton wilt, it is impossible to set up a standard field experiment, as a sterile control cannot be created. In microfield vessels, pathogens act in a natural setting where their harmfulness is amplified by real climatic stresses.

Using this method, it is easy to separate the influence of soil fertility and climate. To do this, vessels are filled with soil brought from a different climatic zone. The large volume of the containers maintains high soil buffering, a crucial factor for adequate plant growth. To reduce dependence on weather whims, the experiment can be combined with drought shelters, plastic covers for soil warming, or gauze canopies for shading.

Working with soil monoliths and specifics of experiments on rice

In agrochemical and land reclamation research, it is more effective to use intact monoliths rather than disturbed (loose) soil. They are extracted from soils of different landscapes and buried at a single test site. This allows the relocation of micro-plots of natural vegetation, along with their native physicochemical and biological environment, to other climatic zones for long-term observations.

Due to the natural heterogeneity of the soil cover, it is necessary to increase the number of experimental replicates. The monolith-replicates themselves are cut on a leveled plot as close to each other as possible. The width of the monolith is made as large as possible, limited only by the lifting capacity of winches and transport equipment. It is pointless to use monoliths shorter than 60 cm — they offer no advantages over loose-filled vessels.

The method has proven itself well in experiments with rice. Experimental paddies are built from brick or reinforced concrete blocks, positioned above or below the soil level. The main task of such structures is to maintain natural temperature in the root zone and regulate the water layer depending on the plant's growth stage.

1. Line the container with polyethylene film to completely prevent water leakage.
2. Fill the prepared container with soil taken directly from rice paddies.
3. Carry out irrigation in strict accordance with the regime recommended for commercial rice crops.