SABI Magazine | Page 30

How to... How to ... take soil samples A step by step guide to the sampling procedure for soil analysis - by Isobel van der Stoep and Mike de Villiers T he analysis of soil samples is a very important tool to the both the irrigation designer and the producer, who has to schedule the correct application of water, fertilisers and corrective measures to the soil in order to optimise both crop yields and the efficient use of water. This editorial will focus on the objectives and soil sampling processes. INTRODUCTION Soil sampling appears to be an extremely simple process, however the samples form the basis of a very important process known as a Soil Analysis. The results of the analysis will provide critical information to the irrigation design team in terms of soil preparation, irrigation scheduling and field management. It is, therefore, unnecessary to stress how important the sampling procedure is to the outcome of the analysis. The location, depth and handling of samples once taken should be done according to a clearly defined plan in conjunction with the Analytical Laboratory and the Irrigation Design Team. Sampling should be an on-going procedure throughout the life of an irrigated field, from soil preparation to maintenance monitoring, in order to apply corrective measures to the achievement of healthy and productive crops. The objectives of soil analysis are as follows: • Planning of irrigation and fertilisation systems • Irrigation scheduling, relating to the calibration of probes and tensiometers • The classification of soils relating to the application of fertilisers and lime • To evaluate soil fertility • To detect and correct imbalances in nutrient concentrations • To assist with the determination of accurate cultivation/ management units. The most important advantage of on-going soil analysis is the ability to monitor changes in soil fertility in order to apply corrective action before nutritional stress occurs. Specialist analytical laboratories, have developed specific norms and procedures to assist with the interpretation of sampling Acknowledgements: We would like to thank the following persons for their assistance with this article Prof. Martin Steyn, Department of Plant and Soil sciences, University of Pretoria Randy Kumasamba, Department of Plant and Soil sciences, University of Pretoria Tielman Roos, Limpopo Department of Agriculture 28 SABI | JUNE/JULY 2016