Table of Contents
Advertisement
Irrigation Water
In agricultural areas it is quite common to find altered values in the chemical composition of irrigation
waters. The problem concerns mostly the high nitrate concentration, usually determined by excessive
fertilization or irrational liquid manure spreading. The analysis of irrigation waters allows us to find
out which are the substances present in major or minor quantity and to organize an advantageous
fertilization plan.
For example, if the quaninty of water utilized for crop cultivation is 250 mm/ha (=2500000 L/ha)
-
and the nitrate (NO
) concentration is 150 mg/L (34 mg/L as nitrate-nitrogen NO
3
85 kg/ha of nitrogen. In choosing type and fertilizer to be used, it is important to consider this
information, in order not to waste fertilizer nor to induce soil pollution.
Nutrients Solutions
The nutrients requirements of the plant are determined by the type of plant, its age and the
environmental conditions. The control of chemical composition of nutrients solutions given to the
plants is an operation that allows a correct preparation of the fertilizer. In analyzing the solution it is
typically necessary to perform a dilution, depending on the concentration of substances.
A dilution factor of 5 usually covers the analysis of residual solution in recycling systems. The nutritive
elements are differently absorbed by the plants, hence the nutrient solution loses substances, becomes
impoverished and must be enriched.
A dilution factor of 10 normally corresponds to the typical values of nutrients solutions. It is therefore
possible to verify that the solution given to the plants contains the correct quantities of nutritive
substances.
8.2. PREPARING NUTRIENT SAMPLES FOR ANALYSIS
Nutrient samples need proper preparation before they can be analyzed by photometric methods. The
three most common problems are:
1. High concentration (samples contain too much nutrient for the analysis method)
2. Turbidity (samples appear cloudy or hazy)
3. Color (samples have a colored tint from soil or impurities)
High nutrient concentration is overcome by dilution of the sample by a known amount with
demineralized water. This is most often encountered when measuring the macro-nutrients: ammonia,
nitrate, phosphorus, and potassium. The following sections explain procedures for diluting samples by
factors of 5, 10, and 50. The table below recommends the dilution procedure and the method to use
based on the estimated nutrient concentration:
-N), soil receives
3
21
Advertisement
Table of Contents
