Crop nutrition management is important in sustainable agriculture. Plants needs food and they get through organic and inorganic nutrients. Soil is a pool for plant nutrients.
But excess amount of these nutrients have detrimental effects on plants growth and development. Agriculture researchers said that before crop sowing farmers should be collected their soil samples with the help of field officers and send these samples in the laboratory. Farmers should be applied nutrients according to soil analysis reports.
Soil sampling is also a good approach but after crop sowing to maturity plant sampling and testing is also a good approach to enhance nutrients efficiency and reduced the nutrition budget. Small farmers are not known about plant sampling techniques.
The prices of fertilizers are too much high and imbalance application without analysis increased management cost. So now it is important to get information about plant sampling techniques in the field.
Plant analysis is basically a tissue analysis for determining nutrient contents of plant tissue at specific stage and time. Through plant sampling we determine true time of application and fertilizer rate.
- Tissue sampling techniques
The following components must be followed during plant sampling.
Specific part or leaves at a particular location on the plant is selected according to crops. In wheat crop it is preferred that after germination 27 to 30 plants are taken for sampling. The second sampling taken at before earing stage.
In cotton crop it is preferred that at seedling stage samples should be collected firstly, at blooming stage 2nd sampling should be done and third sampling should be preferred at appearing of first square. In mango orchards sampling should be done of 7 months old trees and collected 30 to 45 leaves per plant.
In corn crop seedling, tasseling and silking stages are important for taken samples from the field. The plant stage and time of sampling are both vary and important for all crops. The number of leaves per plant or other parts like twigs should be maximum and upper leaves should be taken for analysis. It is considered thumb role for plant sampling.
Avoid take samples from stressed plants. Always choose healthy plants. The plants should not have been damaged by insects, animal attacks and diseases.
Farmers are not collected samples after immediate application of fertilizers. Do not collected border rows or trees for sampling and shade plants are also discouraged.
Some private companies and agriculture sector arranged training for farmers about how to collected soil and plants samples from the field. After sampling, sample preparation protocols must be followed. These protocols are discussed below in detail.
- Plant sampling protocols
Plant sampling protocols included initial handling, washing for decontamination, moisture removal, grinding and organic matter destruction. These steps are elaborated step by step.
1- Plant tissue transportation
Plants part are perishable and must be kept at lower temperature. Plant samples must be kept in clean paper or bags. Lower temperature prevents decay of plants. The working shelf or place must be contaminated free.
2- Sample washing for decontamination
If samples have dust particles, then wash with water. Distilled water and tap water both are used, but in laboratory distilled water will be preferred.
3- Oven drying of samples
This step is performed in laboratory. Fresh samples are firstly dried under shade then kept in oven at 700C for 3 to 5 hours. The temperature is selected according to crops. The dried tissue must be stored in moisture free room before testing.
4- Grinding of samples
For further laboratory analysis small particle size should be preferred to maintain uniformity in samples composition. The tissue is mechanically grinded by grinding machines or pestle mortar.
5- Destruction of plant samples organic matter
It is done by wet acid digestion or higher thermal oxidation. It is compulsory and important step in testing of tissue sampling.
The further processes are selected upon types of testing. All type of macronutrients, micronutrient and heavy metals testing facilities are available in all government laboratories. Nutrients are good for soil fertility but not for soil productivity.
For soil productivity balanced nutrition at right time with right application methods will be required with combination of green manures and organic matter.
The soil, plant and water sampling is key practice for maintaining sustainable agriculture systems.So agriculture universities, extension officers and researchers must be work on spreading awareness about soil,plant and water sampling.
M.Sc. (Hons.) Agriculture/Agronomy
MNS University of Agriculture Multan, Pakistan