Effect of Electrical Conductivity and Spatial Variability of Soil on Crop Productivity

Abstract

The emerging agricultural scenario advocates for balancing of multiple research objectives including productivity, crop quality, safety, livelihood security, protection of environment and biological diversity at affordable cost. Precision farming (PF) is one such viable technological tool which can ensure sustainable development and meet above expectations. PF is an outgrowth of technological developments. PF is the most promising sustainable agriculture (SA) approach known to date and has been hailed as one of the most influential approaches to production agriculture. It epitomizes a better balance between reliance on traditional knowledge and information and management-intensive technologies thus, safeguarding fragile environmental infrastructure. This system can be efficiently explored on the basis of emerging technological tools and sources of information such as GPS, GIS, YMs, RS, soil, plant and pest sensors, and variable-rate technologies (VRTs) for application of optimally customized inputs. Conventionally field is managed uniformly as a whole, without reference to the agronomic variability of fertility or crop growth and development, under the assumption that the field is homogeneous. Whereas, in modern agricultural management practices (AMPs), fields are managed with respect to site-specific variability wherein these fields are delimited into smaller zones called as sub-fields and are managed separately in order to match farm specific agronomic characteristics. In such approach, variations in edaphic and anthropogenic factors including organic matter content, soil nutrient and moisture status, landscape topography of the field (slope and elevation), climatic conditions, cropping history, plant protection needs, as well as past soil management practices etc., is accounted for while developing a management strategy, in order to increase the productivity of land, improve the quality of crop, profitability of the production, reduce the risk of over or under management, conserve the natural resources, and protect the environment. There are a number of spatio-temporal variability mapping technologies including soil mapping, crop mapping and yield mapping. In case of yield monitors, they are fitted on the combine harvester but, these are not developed for all crop varieties and can’t indicate what factors have resulted in bringing variability of yield productivity on a field. Similarly other mapping tools are still evolving and will take time to become fully matured technology for field usage. In contrast soil variability mapping tools are most widely used and are documented for their practical use on fields. Soil ECa mapping is one such most popular technique which is widely accepted for mapping and characterizing spatial variability of soils due to its several advantages such as: ease of operation, rapid measurement, ruggedness, reliability of data, cost effective operation. Several studies have indicated that bulk soil EC measurements can serve as a substitute for soil physical properties including OM, clay content, CEC, and can be used to measure nutrient concentrations in the field. It has also been seen that EC maps are proving useful in improving economic returns to PF. On the software tools side, performance of various spatial interpolation techniques for mapping soil properties has been evaluated by many researchers to improve site-specific crop input efficiency. As it has been now established enough that uniform rate application is inefficient, recent research in PF has focused on use of MZs as a method for variable application of inputs. MZs based farming is efficient and cost effective to yield higher quality and quantity returns in agri-production system. In MZs, homogeneous combinations of potential productivitylimiting factors which have minimal heterogeneity in a particular region are identified. This process mainly answers three questions i.e. source of information to be used for delineation of zones, procedure to be followed for delineating zones and numbers of zones that should be optimal on a given field. Often on some soils ECa has been reported to match crop yield patterns in such zones. Similarly, ECa in conjunction with soil and / or landscape attributes has been used to explain variability of fertility attributes as well as productivity zones and establish their patterns at different scales in addition to identify soil sampling locations. Based on inferences drawn out of literature search, a strong need was felt to undertake PF studies on Indian fields particularly the variability of electrical conductivity and spatial distribution of soil physico-chemical properties in relation with crop productivity. As Indian land holdings are small scale, there is pressing need to establish feasibility of PFTTs on Indian fields in the local conditions where tropical weather is different and moreover a large difference in farming cultural practices exists. Presented work deals with the studies relating to spatial variability of bulk electrical conductivity and soil physico-chemical properties and its influence on crop productivity through use of modern PF techniques and technologies.