In 2000, Australian scientists tricked grapevines into conserving water by drying half their roots. 26 years later, PRD remains a technique that can maintain yields while cutting irrigation by 50%

Water is essential to agriculture, but using it efficiently becomes increasingly important when supplies are limited or affected by salinity. Researchers in Australia developed a way of changing how grapevines are irrigated so the plants receive less water while continuing to produce commercially useful crops.

The approach, called Partial Rootzone Drying (PRD), was developed at the University of Adelaide’s Waite campus by a team led by Dr Peter Dry, Senior Lecturer in Viticulture science, and Dr Brian Loveys of CSIRO Plant Industry.

PRD was developed as a way to reduce irrigation without creating additional problems associated with saline soils.

The Idea Behind Partial Rootzone Drying

The principle behind PRD is to deliberately keep various parts of a grapevine’s root system under different water conditions.

One portion of the roots is gradually enabled to dry while the remaining roots continue receiving adequate water. According to the research described by Dr Dry, this makes the plant react as though a huge portion of its root system is facing drought.

The plant responds by producing chemical signals that cause the stomates to close and minimize shoot growth and leaf area. These changes help conserve water, while the watered roots continue aiding the health and productivity of the plant.

The process can then be reversed. The earlier dry roots can be watered while the roots that had been getting water are allowed to dry. This can prompt the minimized shoot growth and partial stomatal closure again.

By repeatedly switching which side of the root system gets water, growers can maintain one portion of the roots in moist conditions while another remains dry.

Less Water Without Minimizing Commercial Yield

The researchers reported that PRD could significantly improve water-use efficiency. “With grape vines and other crops such as citrus, pears and peaches, we can produce the same commercial yield with half the district average of water applied,” stated Dr Peter Dry, Senior Lecturer in Viticultural Science.

“In most situations we’ve been able to double the water use efficiency, so that has big implications. We are short of water, so if we can get twice as much fruit per megalitre of water, that’s very important,” cited Dr Dry.

Questions About Salinity

South Australian agriculture relies heavily on the River Murray, where increasingly saline water creates an additional challenge for growers. Researchers were therefore interested in knowing how PRD would perform when irrigation water itself contained more salt.

“So far we haven’t done much research on using PRD saline water,” said Dr Dry, “except for experiments where the water is relatively saline, and we’ve had exactly the same results,” he said.

“We’ve assumed so far that because we are putting on half the water, we’re only putting on half the amount of salt on, but I guess the distribution of salt in the soil, and how the roots take up the salt, is one of the issues,” said Dr Dry.

PhD Research Into Water Quality

Two new PhD students were working on comparisons between conventional irrigation and PRD using two different water sources.

“We have 2 new PhD students working on comparisons of conventional irrigation versus PRD using 2 water qualities, River Murray water and bore water,” said Dr Dry. “The bore water is extremely saline, and we’ve got 2 amounts of irrigation so we have 8 treatments in that experiment.”

“One student is going to be looking at the movement of salt in the salt profile; the accumulation of salt, its effect on the soil structure and also the accumulation of salt within the vine itself, both in the leaves and the fruit,” mentioned Dr Dry.

The other student would concentrate on the effect of the irrigation treatments on fruit quality.

“The other will be looking not so much at the salinity but at the fruit quality,” he stated.

Innovation Without a Patent

The development of PRD was also presented as an example of how scientific research can result in practical agricultural innovation. However, turning such a concept into a commercial product does not necessarily guarantee financial rewards for the researchers who developed it.

Dr Dry said the researchers had considered the possibility of commercialisation but explained that the basic idea could not be patented.

“We have looked at that,” said Dr Dry. “You can’t patent this idea.”

He noted that funding was already supporting PhD students, while also expressing uncertainty about how additional research initiatives would translate into financial support.

“We are getting some funding for PhD students so we shouldn’t be complaining too much, but I’m about to write another application, and I’m not quite sure, with these initiatives that you mention, how we’re going to get money out of them. We’re waiting for someone to tell us the cheque is in the mail.”

A Different Way to Think About Irrigation

Partial Rootzone Drying offers a distinctive approach to agricultural water management. Rather than simply reducing water everywhere, the technique alternates irrigation between different portions of a plant’s root system, allowing the plant to respond to drying conditions while maintaining access to adequately watered roots.

The research described by Dr Dry showed potential for maintaining commercial yields while using substantially less irrigation water. Its investigation across different crops, water qualities, and countries also reflected the wider challenge facing agriculture: producing food with increasingly limited freshwater resources.

The work at the University of Adelaide’s Waite campus placed plant responses, irrigation practices, salinity research, and agricultural productivity together in an effort to make better use of every unit of water available.

Source: ScienceDaily

FAQs:

Q1. What is Partial Rootzone Drying?

Partial Rootzone Drying, or PRD, is an irrigation technique that alternates water between different sections of a plant’s root system. One portion is kept relatively dry while another remains watered.

Q2. Why was PRD developed?

PRD was developed to reduce the amount of irrigation water needed by crops. It was particularly relevant to agricultural areas facing limited or increasingly saline water supplies.