Correct administration of nitrogen and irrigation proven to extend yields and cut back leaching

Think about a scorching and dry summer season day, it may need been dry and scorching for a very long time. The birds are singing and the irrigation machines within the fields are operating at full velocity. However what does irrigating crops actually imply for farmers’ yields and the way does it have an effect on nitrate leaching? Researchers from Aarhus College have discovered the reply in information from 1988-1992.

“Now we have labored with a dataset that’s greater than 30 years outdated, however regardless that it’s outdated, it’s nonetheless helpful and related at present. We used the information to delve right into a years-long debate about whether or not irrigation is nice or unhealthy, for instance by way of nutrient leaching,” explains postdoc Loraine ten Damme from the Division of Agroecology at Aarhus College.

On the proper time and place

The query of whether or not irrigation is nice or unhealthy is actually about two issues. On the one hand, irrigation is anticipated to extend the chance of nitrate leaching as a result of elevated irrigation will increase percolation—that’s, it will increase the leaching of extra water into groundwater. However, irrigation has the benefit of accelerating plant development and thus nutrient uptake, which really reduces the chance of leaching. The extra nitrogen the vegetation take up, the much less is left within the soil, which suggests much less leaching. However which of the 2 views is the precise one?

“Our information level to the significance of managing each irrigation and nitrogen accurately. Because of this if you happen to fertilize with the correct amount of nitrogen on the proper time, and also you additionally irrigate on the proper time, you’ll considerably cut back nitrate leaching and you’ll obtain a better yield as properly,” explains Loraine ten Damme.

Conversely, mismanagement of irrigation will trigger elevated leaching and restricted yield. So, as such, there isn’t any clear reply as to whether irrigation is nice or unhealthy. Nevertheless, analysis exhibits that there are good advantages to having a transparent technique on your administration, even when it isn’t all the time simple.

“There are numerous issues that come into play in relation to fertilization and irrigation methods that make it a bit tough to plan. You need to suppose forward, as a result of if you happen to add a specific amount of nitrogen however do not irrigate sufficient, the vegetation will not have the ability to take up the nitrogen. The nitrogen then stays within the soil vulnerable to leaching and also you would possibly as properly have saved the cash on fertilizer. Thus, you probably have fields that may’t be irrigated, it’s best to adapt your fertilization technique, i.e., apply much less fertilizer, as a result of nobody can predict what the climate might be like through the season,” says Loraine ten Damme.

Nitrogen follows the water

The experiments behind the information the researchers labored on passed off in 1988-1992 on coarse sandy soil in Jyndevad. Throughout that interval, there have been years of drought and moist years, which based on the researchers offers them the chance to see what impact irrigation has on grain, seed and straw yield.

“We will see that in years with applicable precipitation, there was no noticeable distinction in leaching, whether or not or not crops had been irrigated. That is apparent since the necessity to irrigate has not been very excessive in these years, however after we have a look at the information for the dry years, we see a giant distinction between irrigated and non-irrigated fields, specific on the comparatively increased ranges of nitrogen utility,” says Loraine ten Damme.

Within the trials, three completely different quantities of nitrogen fertilizer had been utilized to each irrigated and non-irrigated experimental plots. The info from the dry years clearly confirmed that when a crop just isn’t irrigated, elevated fertilization has little impact on crop yield however results in elevated leaching. In distinction, the information confirmed that the irrigated crops may make use of upper ranges of fertilizer, with out the chance of elevated nitrate leaching.

“Usually, nitrogen will comply with the water, and that additionally means in concept that the extra you irrigate the extra leaching you’ll threat, however our research present that that is really not essentially the case. Once you irrigate on the proper instances, crops can take up extra water and extra nitrogen. That manner you might not threat elevated leaching, however enhance crop productiveness,” says Loraine ten Damme.

However do you have to water on a regular basis to extend plant development and cut back leaching?

“No, an excessive amount of water creates anaerobic situations, which signifies that vegetation can drown. Furthermore, if you happen to overwater, there’s a excessive threat that fertilizer nitrogen might be leached through the rising season,” she explains.

The identical goes for nitrogen. You may hold including nitrogen, however sooner or later, you may attain a stage the place the vegetation cannot make the most of any extra, i.e. additional fertilizer doesn’t enhance yield. You attain a saturation stage and something above that might be a waste of effort, cash and can enhance the chance of leaching.

Know your wants

There isn’t any simple answer, as many components come into play when planning your fertilization and irrigation technique.

“As a farmer, you might want to know when your vegetation are rising greatest to be able to fertilize and water accurately to get essentially the most out of your efforts. You additionally must regulate the climate, which is usually tough to foretell, particularly if you wish to plan methods to fertilize firstly of the rising season. Irrigation choice assist techniques assist farmers to quantify the irrigation wanted for the crop in its particular growth-stage whereas minimizing the chance of overwatering. Nevertheless, it is necessary to do not forget that if you happen to’re solely making use of small quantities of nitrogen, then the necessity for irrigation is not that nice, however you probably have a fertilization technique with bigger quantities, you then also needs to irrigate to get the utmost profit from the nitrogen and the utmost achieve by way of increased yields and fewer leaching,” concludes Loraine ten Damme.

The work is printed within the journal Acta Agriculturae Scandinavica, Part B—Soil & Plant Science.