New method developed for monitoring pasture nutrients

Process compares pasture nutrient levels obtained by traditional laboratory methods to readings from handheld NIRS device.

A fast new way of checking nutrient levels in grasslands allows farmers to quickly monitor changes in pasture nutrients and adapt their animals' grazing methods accordingly, according to an announcement from the publishers of Frontiers in Sustainable Food Systems.

By cutting the analysis time from around 16 hours to less than a minute, this relatively cheap and easy approach may greatly improve the sustainable management of grasslands — the main form of agriculture in many parts of the world, and a cheap and affordable source of nutrients for ruminant livestock that, in turn, provide meat and milk for people, the announcement said. Using this new method, research being published in Frontiers in Sustainable Food Systems shows that overgrazing pasture to below 7 cm significantly reduces the amount protein and digestibility of the grassland.

"Real-time nutrient monitoring can provide a more timely and adaptive pasture management than is currently feasible for farmers and should lead to productivity gain," said lead author Matt Bell, assistant professor at the University of Nottingham School of Biosciences in the U.K. "Using this new method of checking nutrient levels, we show that over-grazing or over-harvesting pastures will significantly reduce protein levels and its digestibility, which will be detrimental to the productivity of the land."

In many parts of the world, grassland is the dominant form of agriculture, and it is also one of the largest ecosystems, covering around 40% of land on Earth. Changes in pasture nutrients over the growing season are not typically monitored, the researchers said, but doing so may help farmers make the best use of this natural resource.

Bell and his team of colleagues at Nottingham recognized this problem and have been working on a solution.

"Grass provides a cheap and affordable source of nutrients for ruminant livestock, which, in turn, produce milk and meat for humans. To manage pasture most effectively, we need a tool for frequently monitoring pastures across fields and over a spring/summer growing period that is quicker, easier and cheaper than traditional laboratory methods," Bell explained. "To do this, we calibrated a handheld near-infrared spectroscopy (NIRS) device to measure nutrients in pasture."

This process involved the comparison of pasture nutrient levels obtained by traditional laboratory methods, which require the use of large, specialized equipment, to the readings given by the relatively quick and simple handheld NIRS device. The NIRS technique measures the spectrum of energy reflected from a sample illuminated by white light, providing information on different nutrient levels in less than a minute.

Using this new method, Luca Mereu, co-author of this research on an Erasmus internship in the U.K. from Italy, collected samples at the University of Nottingham farm to assess changes in pasture nutrients and the factors that may have caused these changes. The results showed that a decline in the height and cover of pasture were associated with lower digestibility and reduced concentrations of protein.

"Intensively grazed pastures should avoid going below a height of 7 cm, otherwise nutrient intake by the animals will be limited. Below this height, the composition of the grass is more stem and residual plant material than vegetative plant material," Bell said.

"Our study confirms that this new handheld NIRS technology can be used to inform better grassland management decision-making and the utilization of pastures for sustainable production," he continued.

This new approach to nutrient monitoring is also expected to lead to new areas of research.

Bell explained, "We wish to investigate other factors potentially influencing changes in pasture nutrients such as botanical composition, different grazing animals and variability within a day. This may help farmers to decide the optimum timing for grazing by sheep and cattle as well as silage management."