36005.ART
October 2016

CLIMATE CHANGE REQUIRES FARMERS AND GROWERS TO HAVE A BETTER UNDERSTANDING OF THE WATER-RELATED CHARACTERISTICS OF SOILS

Climate change is a reality that we must learn to live with, as illustrated by the report ‘Managing the land in a changing climate' published in July 2013 by the UK's independent Committee for Climate Change's Adaptation Sub-Committee; this report includes a disturbing prediction that farming could suffer a shortfall in water supply by 2020. On the other hand, the UK has had a number of wetter summers in recent years, so we have to be prepared for both drought and wet weather.

To cope with these conditions, farmers and growers can reconsider which crops and varieties to grow. They can also combat drought conditions using only a limited water supply if they are smarter about irrigation. Optimising irrigation requires both an understanding of the plants' needs and a detailed knowledge of the water-related characteristics of the soils - which can vary significantly from one area to another, even within a single field. Precision farming is already employed by some farmers in the UK to optimise the use of fertilisers, thereby maximising yields and minimising costs, and a similar approach to irrigation could be beneficial, particularly for fruit and vegetable production.

A key characteristic of any given soil is its soil water isotherm - also referred to as soil water characteristic curve (SWCC), moisture release curve, water retention curve or pF curve. This characteristic represents the relationship between the soil's water potential and its water content. A semi-log plot of these parameters produces a straight line, the slope of which indicates whether the soil will shrink or swell as it dries and takes up water, and it can also be used to calculate specific surface area for the soil. Soil water isotherms have seldom been used in the past by UK farmers and growers because it has been a laborious, time-consuming and costly process to generate each isotherm. Fortunately, however, the relatively recent introduction of the Decagon Devices AquaLab Vapour Sorption Analyser (VSA), which is available in the UK through Labcell, automates the process, enabling a complete adsorption/desorption isotherm to be generated from up to 200 points in around 48 hours. In addition, the latest version of the VSA benefits from a static feature that enables humidity to be held constant so that a study can be made of the way a soil takes up water into its crystal structure (2:1 clays), and water content change can be monitored over time. The affordable, benchtop VSA is easy to use, clean and calibrate, so it presents new opportunities for farmers and growers who are eager to gain a far better understanding of their soils and implement smarter irrigation regimes.

For in-situ monitoring of matric potential (water potential), Decagon Devices offers the MPS-2 sensor that utilises a capacitive measurement technology to monitor the water content of a known ceramic matrix, from which the soil's matric potential can be inferred. This sensor achieves good accuracy in the measurement range of interest, giving a better indication of plant-available moisture than measurements of water content.

Of course, if the soil water characteristic curve has already been generated for the soil in question, then water potential can be established simply by measuring water content and converting this using the characteristic curve.

Plant research

Plant scientists are also researching ways to optimise irrigation without compromising yield or quality.

Today there is a wealth of sensors and instruments available for measuring moisture-related parameters and characteristics in soils, but the maximum benefits can only be attained if the data is subjected to rigorous analysis. Raw data can be difficult to interpret, and building spreadsheet-based analysis tools is time-consuming and prone to errors. To overcome this problem, Decagon Devices has developed its DataTrac 3 soil moisture analysis suite for manipulating data and generating easily-interpreted graphs. If appropriate, data is updated in real time, so users can monitor what is happening in case any manual intervention is required. In addition, users can add their own notes that will help them to understand the information at a later date. If Decagon Devices Em50 and Em50G loggers are being used, the DataTrac 3 software can automatically receive and organise the data to minimise the need for operator inputs, which also avoids the risk of errors being made.

It cannot be stated with 100% certainty that climate change will cause water shortages for farmers and growers in the future, but the probability is sufficiently high that action should be taken. If water is in short supply it must be used wisely and not wasted, so it is vital to have a detailed understanding of the relationships between plants, soil and moisture. The technology is readily available, affordable and easy to use, so farmers and growers are urged to start gathering data in order that they can implement a smart irrigation regime and continue to produce crops with the right yield and quality, even in the event of water shortages.

Contact Labcell to request more information about the Decagon Devices AquaLab Vapour Sorption Analyser and other instrumentation by telephoning 01420 568150 or email mail@labcell.com. Alternatively, find out more and download data sheets from Labcell's website at www.labcell.com.

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