Chapter 1 Soil Health and Nutrient Management
1.5. S OIL T ESTING FOR S OIL H EALTH M ONITORING
Conceptually, the intrinsic health or quality of a soil can be viewed simply as ‘its capacity to function’. Soil health could be defined as ‘the capacity of soil to function within the ecosystem
boundaries, to sustain biological productivity, maintain environmental quality and promote plant and animal health’. Many a time, the state of the soil is also explained loosely in terms of soil health, soil productivity, or soil environment. On the other hand, soil quality connotes the soil’s usefulness for a particular purpose over a longer time scale. Nonetheless, the terms ‘soil health’ and ‘soil quality’ are often used inter-changeably; farmers prefer the former and scientists the later. Even use of the joint term ‘soil quality/health’ has been proposed for a better communication, knowledge sharing, and understanding of the management techniques by different stakeholders. The basic soil health indicators should (i) integrate soil physical, chemical and biological properties and processes; (ii) be sensitive to variations in management;
and (iii) measurable or accessible by as many people as possible.
In Indian context, monitoring of soil health is often considered synonymous to soil testing, carried out for assessment of soil fertility status or appraisal of soil problems such as acidity, salinity or alkalinity. The infrastructure for soil health monitoring has only over the last 3 years begun to be upgraded to support the analysis of even minimum soil fertility parameters required for formulation of balanced fertilizer schedules; and measurement of biological and physical characteristics of soils by soil testing laboratories would require further strengthening &
therefore time. Research laboratories, however, study the impact of input use, cropping systems, climate change, etc. on different soil health parameters.
Soil testing is a time-tested tool for soil fertility evaluation and monitoring. It also helps restoration of depleted soils by offering soil-test based recommendations on plant nutrients and amendments. Soil testing operates on the principle of probability, meaning, if all other factors of productivity are at the optimum, there is high probability to obtain more profitable response to applied nutrients based on soil testing than to those applied on ad hoc basis. So far, the results have been impressive, provided the recommendations are formulated suiting the specific crops grown. Began in 1955-56, soil testing service in India have constantly expanded over the years, and more particularly since the last 3 years. The present network is described by 1735 soil testing labs (STLs) (1459 static labs + 276 mobile labs) with an annual analysing capacity of 22.24 million soil samples (Figure 1.6).
Figure 1.6 Expansion of soil testing service in India
In addition, soil testing facilities have also been created at almost all Krishi Vigyan Kendras (KVKs), numbering 676. The state agricultural universities (SAUs), some of the ICAR institutes and private/cooperative industrial & service organisations also offer soil testing service on a limited scale. In order to further strengthen the service in different states, 5846 mini labs (digital soil testing kits) have been sanctioned during the year 2016-17 onwards by the DAC & FW. Of this network, only 911 STLs are equipped with micronutrient analysis facilities. With the governments’ initiative to distribute soil health cards (SHCs) to ~138 million farm holdings once in every cycle of 2 years, soil testing service has come to occupy centre stage, and is now considered critical infrastructure for soil health management.
1.5.1. Weaknesses of Soil Testing Service
Despite large network of STLs and personnel engaged therein, the service is yet to gain desired mass acceptability. As a result, the voluntary demand for soil testing is low, as even innovative and resource-rich farmers are often not enthusiastic to get their soil tested for fertilizer use and soil amendment decisions. This is due to lack of trust in the services offered by STLs, and also on account of not realizing the importance of soil test based nutrient-management. Soil testing, therefore, is yet to transcend beyond a government-driven service However, all stakeholders have since the role out of comprehensive and universal SHC scheme in 2014-15 begun to pay greater attention. Further, among a large number of farmers there is now greater awareness about its tahnks to aggressive advocacy & promotion by the government over the last 3 years, and can become a demand driven initiative at the farmers’ level. This responsibility on the shoulders of all concerned agencies including researchers, State Departments of Agriculture, fertilizer industry, and policy makers at national level. A critical analysis of the major weaknesses of soil testing service is presented hereunder:
Soil sampling protocols
Soil sample is the first and foremost component of soil testing that decides ultimate value of
the service to the farmers. As small amount of soil in the form of sample represents the entire delineated area, a poor soil sample becomes the primary source of error in soil testing and interpretation of results for nutrient recommendation or any other intended purposes. Prior to initiation of SHC Scheme, no well-defined norms for sampling density, time or frequency was laid down. As a result, the soil test data could neither be used meaningfully for generation of area-specific soil fertility maps, nor for monitoring of management-induced temporal variability in soil fertility status.
Since universal coverage of individual farm holdings for sampling and analysis is not possible with existing technology & infrastructure, soil sampling norms need to be standardized. The GPS-enabled sampling at a uniform grid of 2.5 ha for irrigated areas and 10 ha for rainfed areas envisaged under SHC Scheme is a welcome initiative. However, the sampling protocols can be further refined so as to capture maximum variability in soil fertility and generate site- specific prescriptions.
Lack of farmers’ participation in soil sampling
As soil samples are collected by the extension personnel without farmers’ involvement,-often without knowledge of the farmers, they obviously remain unconcerned, and seldom own the outcome. In the absence of a feedback mechanism, the benefit accrued to the farmers in terms of adoption of soil test-based recommendations cannot be evaluated properly to bring in need- based improvements, if any in the service.
Poor analytical facilities and their maintenance
Majority of STLs analyze soil samples for pH, EC, organic C, available P and available K status, and offer recommendations for NPK only, as not all STLs are as yet equipped with atomic absorption spectrophotometer (AAS) – an essential equipment for micronutrient analysis. Other analyses are also done often using very old and outdated equipments. Some of the STLs having AAS or inductively-coupled plasma spectrophotometer (ICP) are not able to generate quality data on micro-nutrients for lack of support services such as uninterrupted power supply, utmost care in collection, processing and storage of soil samples, absence of analytical grade reagents, double distilled water, etc.
Repair and upkeep of lab equipments is another major challenge in the STLs located in remote areas or in the KVKs. Where needed infrastructure has been put in place under the soil health management (SHM) scheme, over the last about 3 years, the critical weakness that remains to addressed in absence of appropriately qualified and adequate number of personnel at the laboratories.
Quality of analysis
The quality of soil analysis is extremely important for the desired impact of soil testing service.
The quality of analysis in the STLs is often compromised on account of inadequate infrastructure, operating facilities, poor human resource, and/or lack of essential support services. Besides, there is no organic linkage between staff who test the samples, and the extension staff who collect the sample. In such cases, soil testing simply meets the set targets,
not the farmers’ expectations. Unless soil test data is reliable and accurate, fertilizer prescriptions are unlikely to perform in the field as expected.
Poor and incomplete fertilizer prescription
One of the most important reasons for poor salability of soil testing service among the farmers is sub-optimal and incomplete fertilizer prescriptions offered by the STLs. This may fail to meet high yield or high profit aspirations of the farmers. The recommendations as given in the package of practices of different states are generally confined to NP or NPK, and this is not enough in current situation of widespread multi-nutrient deficiencies.
Since fertilizer recommendations with “one size fits all” approach overlook location-specific and crop-specific nutrient status the outcome may turn out to be only a shade better than farmers’ fertilizer practice. In result, it may not yield the desired impact on yield levels or soil health and consequently become a bad demonstration. A bad demonstration is worse off than no demonstration. Since SHCs follow general fertilizer recommendations of different states as modified by soil test results, the old fertilizer recommendations need to be revised so as to offer robust recommendations to the farmers, and in sync with local agro-climatic conditions.
Fertilizer prescriptions based on targeted yield approach of ICAR’s AICRP on Soil Test Crop Response Correlation (AICRP-STCR) take into account nutrient demand of the crop for a targeted yield goal and relative contributions from soil and fertilizer sources. Fertilizer adjustment equations of the AICRP–STCR may be used as these suggest a change in fertilizer requirement with changing yield targets. This approach, however, offers fertilizer recommendations for moderate yield targets only. Hence, AICRP-STCR as well other approaches need to be examined critically and improved so as to keep them relevant for high production agriculture. As examined in the succeeding Volume VIII, dealing with production targets across the crops, it will be seen that productivity gains ar the only rational approach to achieving higher production, since the scope for bringing additional land under cultivation is not much.
Poor human resource
Soil testing is a specialized job which requires involvement of a subject matter expert with thorough understanding of soil test methods, data interpretation and formulation of recommendations. Unfortunately human resources deployed in several STLs possess inadequate knowledge and skill essential for the job. Sometimes trained officers heading the STLs are replaced with those not having even a basic training in soil testing. Also, there has not been a provision for regular training/refresher courses for the STL staff, prior to launching of SHC Scheme. This needs to be addressed suitably on priority.
Weak linkage with research institutions
Professional linkages of the STLs with research institutions (ICAR or SAUs) are either absent or very weak, resulting in restricted transmission of any new knowledge or developments from the latter institutions to the former. Simultaneously, research institutions too do not get feedback from the STLs. Two way diffusion of information and knowledge would benefit both
to the advantage of soil test system as a whole. It would help to create effective linkage/interface amongst organisations associated with soil testing service (mostly State Departments of Agriculture and ICAR institutes and SAUs).