I am reading some literature which says sampling should be done when soils are at field capacity. This ensures appropriate interpretation of field penetration resistance measurements, facilitates proper mixing of subsamples, and prevents soils from smearing during sampling and transport.
This makes me think what are appropriate conditions, precautionary measures and pre-preparation for taking samples from a 60 acres.
Dr. Srivastava's references are very good. In my experience, it is physically difficult to be in the field when the ideal conditions occur. My best results have been when the soil is somewhere between field capacity on the higher moisture side and somewhere just above the permanent wilting point moisture content of the soil. I use push probe tools so this is the moisture range that is where these tools work best. A lot depends on the depth of sampling, too. There isn't one good optimum condition at which to sample although there are ranges of conditions where there are good conditions. Sampling in the moisture range that I mentioned facilitates crushing of cores and mixing and also packaging and other handling of the samples.
Sampling should be avoided just after fertilization, amendment application and immediately after rainfall. If fertilization is intended at planting, sampling should be carried out before planting. Sampling taken during the crop growth period will help in knowing the in situ nutrient status of the soil during different stages of plant growth. For comparing analysis, it is important to take sample at similar time, year after year at regular intervals.
Depth-wise soil samples should be taken as per needs. For analysis of the available macro and micro-nutrients that are related to crop growth and nutrient uptake, sampling is done to a depth of 30 cm. In some cases , especially in irrigated areas, sampling is done to a depth of 60-100cm, especially for monitoring NO3-N leaching and salinity. Soil samples especially for micro-nutrient analysis should be taken using a stainless steal auger. For rhizosphere sampling carefully excavate the root specimens from the soil, cut the root from the larger connecting roots with the knife or scissors, place the root and adhering soils in a plastic bags, a tag label is dropped in to it with all details in all collected samples and transport the samples to the laboratory in ice-cooled box or cardboard boxes for analysis.
While mapping nutrients, issue becomes still very tedious when changes in nutrients status are to be evaluated over space and time. Relocating the same grid points for assessment of temporal changes in soil nutrient status needs a huge skill and experience. We also need soil fertility limit vis-a-via crop to superimpose over spatial variogram for specific nutrient to delineate management zones...
Dear Dr. Srivastava ,
Thank you for link . it is very important information to take samples
- Badges
- Science topic
- Similar topics
- Agriculture
- Soil Science
- Soil