Storing water to cope with droughts

Summer 2018: In Sweden, temper­a­ture records were being rewritten almost daily. Some areas went for three weeks without rain, a first in this northern climate. Nicklas Göransson, farming 300ha of pota­toes, onions, carrots and grain, saw his yields fall by 25% during the season as his pivot irri­ga­tion did not allow him to coun­ter­bal­ance the effects of heat, due to a lack of water. “We couldn’t irri­gate the small grain,” he recalls a year later.

His pota­toes yielded only 30-40t/ha, 10t less than expected, and his onions 40t/ha instead of 50t. Barley yields fell by 25%. Still, he did better than many of his colleagues – according to the Lant­männen coop­er­a­tive, the average Swedish grain yield fell by 45% in 2018.

Warming

Throughout Europe, droughts are putting more and more farmers under pres­sure. In a scenario of high carbon emis­sions, heat waves like those of the last two years, or even more intense, will be repeated every two years in the next 30 years, according to the Euro­pean Envi­ron­ment Agency. This would increase irri­ga­tion needs by 25% by 2100. In the southern part of the conti­nent, non-irri­gated field crops could expe­ri­ence yield drops of up to 50%.

A worrying situ­a­tion. However, average annual water resources remain stable in most coun­tries, and have even increased in some (info­graphics p12). Preserving water when it is avail­able in order to use it later is there­fore a common-sense approach. Reten­tion basins, hill­side reser­voirs, and agro­nomic solu­tions exist, and more and more producers are consid­ering them.

Sweden: invest­ment in the future

In early 2018 Mr Göransson started construc­tion of his water reten­tion system, which was completed a year later. It consists of a 30,000m³ drainage-fed basin coupled with a wetland, and is connected to the nearby Helgeån River. The drained water flows into the basin and when it reaches satu­ra­tion a pipe redi­rects excess water to the marsh, where it is stored. Conversely, if there is not enough rain to fill the pond and marsh­land, water from the Helgeån River can be used.

“It’s an invest­ment in the future,” says the producer. Two thirds of his irri­gated areas are still supplied by a self-drilled well, but the neigh­bouring town of Kris­tianstad is plan­ning to use ground­water as well. Mr Göransson there­fore expects quotas to be set on how much ground water can be taken out. “Before the reten­tion system was built, I was much more vulner­able to future regu­la­tions and restric­tions.”

He under­lines the sustain­ability of his approach: “It would not be sustain­able in the long term to use only pure drinking water to irri­gate our crops. I am not allowed to use more water than my farm produces. But the marsh­land brings biodi­ver­sity.” The 2.5ha of wetland was eligible for aid money covering 90% of the estab­lish­ment costs, namely SEK2.5m (£209,000).

On the water consultant’s map, Nicklas Göransson points out his 2.5ha wetland and the connected 30,000m³ water dam, part of which is under sea level.

On his farm in Gärds Köpinge, Nicklas Göransson inspects drainage pipes from his fields which lead down to his dam and wetlands, which are also connected to a nearby river.

France: a basin for vegetable growing

Further south, France has not been spared from the changing climate. In 2019 alone, the FNSEA (National Feder­a­tion of Farmers’ Unions) esti­mated economic losses due to the drought to be €80m (£72.5m). In Print­zheim, Alsace, Anthony Carbi­ener can testify to this. The young farmer and his parents work 91ha, mainly growing vegetable crops (squash, pumpkin, cabbage, cour­gettes, asparagus, Chinese cabbage, and lettuce). Deli­cate produce in the context of climate change.

“The farm began market gardening in 2000,” reports Mr Carbi­ener. “We never needed to irri­gate until 2003. Now we’ve run out of water.” The first drought expe­ri­ence was in 2014. “And from 2017 onwards, we have been hit hard.” Plants are not only impacted by the water deficit but also by the heat, which is unavoid­able. “Blooming crops are the ones that suffer the most. During the last heat wave, they started to wilt as early as 10am.” In the green­house where the family grows toma­toes, peppers and aubergines for direct sale, the temper­a­ture rose to 70°C.

In 2018, the family decided to build a reten­tion basin to make up for the lack of water – having just lost 70% of their vegetable harvest. “The problem is that Print­zheim doesn’t lie over any ground­water,” explains Mr Carbi­ener. “We tried to drill a well, but we’d have to go down to 600m to get the 70m³ per hour we’re looking for.” Instead, the farm invested €55,000 (£50,000) in a 60 x 60m basin, five metres deep, with slopes of 35°. That’s a 12,500m³ reser­voir, making it the largest arti­fi­cial basin in the region. It will fill up directly thanks to the abun­dant winter rains, and through the drainage water from the surrounding 150ha.

Effi­cient irri­ga­tion

“The volume of rain shifts throughout the year,” observes the vegetable grower. In the middle of the cabbage harvest, intense rain­fall compli­cated field work. And it’s getting harder and harder to get onto the fields in the spring. “At the begin­ning of April, we had a long warm period, followed by a period of heavy rain at the begin­ning of May. And then, from 15 May: No more rain until September,” says Mr Carbi­ener. “This has been the recur­ring pattern for several seasons now.”

The basin allows him to irri­gate between seven and 15ha, depending on the year. This is not a guar­antee against drought but does provide more room for manoeuvre. “The volume of water would allow more land to be irri­gated, but the next plots are 4km away. It would be too expen­sive to pump water all that distance. Then we have to opti­mise our crop rota­tion.”

Preserving water in the ground is another possi­bility. “We started mulching the cour­gettes for weed control, and we saw a reten­tion benefit.” Mr Carbi­ener now system­at­i­cally uses a 1.5m nylon sheet on both sides of the row along with drip irri­ga­tion. “If cour­gettes do not have a regular growing cycle, the fruit will be deformed and impos­sible to sell at the main buying centres.” The measures put in place have enabled him to halve the volume of irri­ga­tion water required.

For several years the farm has also been working to improve its soil organic matter. “In market gardening, we spread compost at a rate of 60m³/ha every year.” After harvest, nitrogen fixing crops are sown. “Times are changing rapidly, and not every­body will be able to cope with it, but we’re already seeing the bene­fits,” says Mr Carbi­ener.

Germany: natural water reserves

At the begin­ning of December, not far from Berlin, the east wind freezes you right down to your bones. It’s hard to believe that Peter Kaim, who runs a mixed crop/livestock oper­a­tion in Nauen with 1,000ha and 170 dairy cattle, had to cope with a heat wave last summer. And yet it was his region, Bran­den­burg, that suffered the most from the heat wave in  Germany. It rained more than in 2018, but not enough to make up the deficit. “We really have had two bad years behind us,” he says. In April 2018, spring “never came”.

“We went straight from winter to summer. Then there was almost no rain all summer,” says Mr Kaim. On the non-irri­gated land with sandy loam and silty-sandy soils, yields were heavily affected: -30% in barley, -50% in corn, -70% in English ryegrass. Only a few plots on a former peat bog drained in the 18th century, where the ground­water level is higher, did better. “The climate has been changing for 25 years,” says the farmer. “I can’t change anything about that. On the other hand, I can change the way I think and work.”

Since 2007, Mr Kaim has been grad­u­ally moving towards minimum tillage, with the aim of saving water, limiting erosion and increasing humus levels. In the begin­ning it was not the weather that moti­vated him to change his system but the fall in rye prices. The goal was to reduce his work­load. “After the first seeding without tilling, I could see that the crop was growing well.” Mr Kaim quickly recog­nised the bene­fits of this tech­nique for soil health and its water cycle.

Strip-till and interim crops

He reserves several plots for trials. Mr Kaim has observed the effect of the delay between tillage and sowing on yield (-20% in rape­seed for a 10-day differ­ence). Where he does culti­vate he sows the crop right after the culti­vator has passed over, in order to leave the soil open for the shortest time­frame possible to avoid water loss. Last summer, he even worked overnight to limit evap­o­ra­tion.

For the past three years, he also used strip-till as an alter­na­tive to direct seeding. The distur­bance to the soil is minimal: The machine only opens it precisely where the row of seeds is sown and adds slurry if neces­sary. The plant bene­fits from the localised organic fertiliser and the preserved humidity, as the soil remains mostly covered.

In addi­tion he has adapted rota­tions to simplify cultivation tech­niques. Mr Kaim usually follows rape­seed with no-till rye, corn, winter barley and, finally, wheat. But this is just one possi­bility among many. “Rota­tion is the system’s corner­stone. With more crops, it’s easier to juggle.” Rape­seed is only grown every five years.

In each case, he weighs up the pros and cons of direct seeding and – based on the specific condi­tions of each plot – decides whether to incor­po­rate the residues. Many farmers still leave their fields uncov­ered during the winter months to take advan­tage of freeze-thaw. But Mr Kaim considers the approach to be outdated under current climate condi­tions. “Soil isn’t meant to be bare. It should stay covered to prevent it from drying out.” The closed vege­ta­tion cover also prevents rain­drops from hitting the soil like a hammer, which reduces water runoff: The farmer’s goal is to ensure that the rain will infil­trate in the square metre where it falls.

Delaying the drought

Under­sown crops have proven to be very useful on plots subject to erosion. If it rains in autumn, they can even be harvested. Other­wise, they remain in place until the begin­ning of the vege­ta­tive period. In this way, they play their anti-erosion role “but don’t take winter water,” says Mr Kaim.

Over the past few years he has discussed his approach with colleagues from the region and compared different systems. Their corn has a better start than his strip-till corn but the situ­a­tion reverses around mid-June. “Their soil has no more water. Our corn stays good for longer.” Here, collecting rain in a basin is not an option, but Mr Kaim is consid­ering building dykes in the former peat bog drainage network to stop runoff. “I hope, as a result, to delay the drought by a week. It’s not much, but it’s some­thing.”

However, for him, the main adjust­ment vari­able in the face of future droughts remains agronomy. “It is essen­tial to preserve natural water reserves,” he empha­sises. The soil is indeed the first tool for storing water.