Organization and methodology of conducting agrochemical field experiments

Any new technology or fertilizer requires field testing. A field trial helps to understand how specific conditions and agricultural practices affect yield and product quality on your farm. In agricultural chemistry, it is used to study the efficiency of fertilizers and chemical ameliorants on plots with uniform soil fertility and a specific soil type.

Stationary and production trials: what is the difference

Trials are divided into two key types depending on where they take place and what tasks they solve: stationary and production. They differ in plot size, measurement accuracy, and the volume of accompanying analyses. The choice of trial type depends on the goals of the farm or research organization.

Stationary trials are established by research institutions on permanent plots. Here, they study in detail how fertilizers affect yield and quality through direct and residual effects, as well as how nutrients transform in the soil. For such studies, it is mandatory to even out the plot's fertility, mark the boundaries of the plots with benchmarks, and follow the crop rotation adopted in the region.

Production trials are conducted directly in the fields of agricultural enterprises. Science uses them to verify the most effective options from stationary studies in real production, while farm agronomists use them to get answers to their practical questions. Requirements for them are less stringent, and the plot area is significantly larger.

• Total plot area in stationary trials — 100–250 m²
• Net plot area in stationary trials — 80–150 m²
• Plot area in production trials — 500–5000 m²

By duration and objectives, stationary trials are subdivided into two types:

• Basic — long-term studies based on detailed programs within a crop rotation. They require strictly homogeneous soils and high precision.
• Preliminary (indicative, temporary, short-term, reconnaissance) — short-term auxiliary trials outside of crop rotation. They are needed to prepare schemes for basic trials, and only yield is measured in them.

Methodology and accompanying analyses

For the trial results to be useful, it is important to properly organize the accompanying studies. Chemical analysis of the soil shows how typical the trial plot is for the farm or zone. Plant analysis allows evaluating the effect of fertilizers on harvest quality and nutrient dynamics.

In production studies, the program of accompanying work is simplified and reduced to several sequential stages:

1. Perform soil analysis before establishing the trial (or use data from previous agrochemical surveys).
2. Mark the boundaries of the plots and the entire trial area.
3. Perform sowing, fertilizer application, and plant maintenance in accordance with the trial methodology.
4. Determine the structure of the resulting harvest after the end of the growing season (plant sample analyses during the growing season are not conducted).

By the number of factors studied, trials are divided into single-factor and multi-factor. In a single-factor trial, only one indicator is changed against a constant agrotechnical background, strictly observing the principle of the single difference. This is how specific types and forms of fertilizers, their application rates, timing, and methods of application, as well as cultivar responsiveness, are tested.

When planning a field trial, it is important to immediately decide on the number of factors. Single-factor schemes are simple, but if you need to understand how the fertilizer application rate interacts with its timing, you will have to set up a multi-factor trial. It is more complex to record and provides more options for analysis, but this is the only way to see the mutual influence of different agricultural practices on yield.

By the time of execution, trials are divided into short-term (one-year) and long-term (multi-year). A short-term trial evaluates the effect of fertilizers only during one season, without considering the residual effect in the second year. Such studies can be conducted both in research institutions and directly in the fields of farms.

Long-term trials allow evaluating the residual effect of fertilizers on subsequent crops in a crop rotation. They study both single applications and the systematic accumulation of nutrients in the soil. Only in long-term studies is it possible to track the cumulative effect, the influence of liming, gypsum application, or the dynamics of soil cultivation.

• Weather testing in short-term trials — 3–4 years
• Duration of long-term trials — from 10 to 50 years or more
• Area of small-plot trials — from 1 to 20 m²

Geographic coverage and size of experimental plots

In terms of territorial coverage, trials are divided into single and mass trials. Single trials are established at a specific location according to an individual design to test local hypotheses. Mass (geographic) trials are conducted using a unified design simultaneously in several regions to understand how soil and climatic conditions affect the effectiveness of different forms, rates, and methods of fertilizer application.

The size of the experimental area determines the technology used in the field. Based on this criterion, trials are divided into standard field trials and small-plot trials. The latter require a special approach to evaluating results due to the small size of the area.

If the plot size allows for the use of standard agricultural machinery, the trial is considered a standard field trial. In this case, the agricultural technology adopted by the farm is fully observed on the plots. This eliminates the influence of artificial factors on the final yield.