LW-R-6: Agricultural irrigation | Umweltbundesamt

LW-R-6: Agricultural irrigation

Under climate change conditions, the need for irrigation is likely to increase and extend to additional crops. In Germany, both the terrain fitted with irrigation technology and the actually irrigated terrain have increased since 2009. In 2019, 506,480 ha of outdoor cultivation areas were irrigated. Frost protection irrigation is not included in these figures.

Irrigated terrain on the increase

A fundamental requirement for high and stable agricultural yields is an adequate supply of water. The cultivation of potatoes and the production of vegetables, and also the cultivation of special crops are particularly worthy of irrigation. In many regions, marketable qualities and stable yields can only be achieved by using additional irrigation of fields in need of water. Two adverse climatic trends can already be observed today in respect of adequate water supply for agricultural crops during the main growth period, which are of crucial importance for the development of good yields: On one hand, at least regionally, (early) summer precipitation is in decline, while on the other, precipitation can fall increasingly as heavy downpours, thus making the availability of water for plants even worse (cf. Indicator BO-I-1). Both developments have adverse effects on the water supply available for agricultural crops. The agricultural sector can, among other things, ensure an increase in soil moisture by cultivating more drought-tolerant varieties and by employing adapted processes of (conserving) soil cultivation and humus enrichment (cf. Indicator BO-R-1). However, the impacts of such agronomic measures can be very limited depending on site conditions. Another option is to reduce water bottlenecks by making the irrigation of agricultural crops more efficient.

The need for irrigation of agricultural and horticultural crops usually arises as a result of extraordinarily long periods of dry weather or in regions where the meteorological conditions (for instance owing to low precipitation levels) and the soil conditions are generally unfavourable. Moreover, it also depends strongly on the relevant crop species grown whether additional irrigation is needed owing to crop-specific water requirements. Regions with high irrigation requirements are not necessarily drought areas. The (future) development of irrigation requirements and the irrigation actually carried out will also depend on the ‘crop mix’.

In 2015 some 451,800 ha of outdoor cultivation terrain was irrigated in Germany. In 2019 this value had already risen to 506,480 ha. Compared to 2009 values, this is an increase by 36 %. These figures do not include any areas where frost protection irrigation was carried out; nor do they include any cultivation areas under high, walkable protective covers, such as greenhouses. With almost 55 %, Lower Saxony is the state with the highest proportion of land nationwide where irrigation plays the greatest role, followed by North Rhine-Westphalia with 10 %. In all the other Länder, this proportion is only up to 6.3 %.

By comparison, in 2015 and 2019, the areas – equipped with irrigation technology and where hence irrigation actually took place – increased further, amounting to 676,400 ha and 768,317 ha respectively. With 14 %, Lower Saxony was the state with the highest proportion of irrigatable terrain compared to the total of terrain in agricultural use, while the region of Lüneburg came top of the leader board with 25.6 %. Whether irrigation actually takes place in a particular year depends on the volumes of rain falling, but also on cost-benefit calculations carried out by the businesses concerned, and not least on the volumes of water available in the region concerned. In the drought year of 2019, 66 % of irrigatable terrain was irrigated, whereas in 2015, the proportion had been lower, amounting to 58 %. The fact that in the region of Lüneburg the cultivation of crops requires such intensive irrigation, is due to the following reasons: That particular area is one of Germany’s areas most threatened and affected by drought, although the same might be said, if not even more so, of regions located in the more easterly parts of Germany; however the areas affected are distinctly smaller there. In fact, the region of Lüneburg is one of the main potato-growing areas in Germany. In the district of Uelzen more than 20 % of arable land is used for the cultivation of potatoes. The soils are sandy and therefore have very limited water retention capacity. Irrigation trials in Lower Saxony have demonstrated that both wheat, winter and summer barley as well as potatoes are particularly vulnerable to drought, which can cause distinct losses in yields. However, optimum irrigation of potatoes produces the highest profits. This crop, followed by ‘Braugerste’ (brewers’ barley), is considered the crop most worthy of irrigation.

In order to mitigate any future conflicts of interests arising in the use of water among competing sectors, and also to ensure that limited water resources are used sustainably, the utilisation of water-saving irrigation technologies is indispensable. According to a statistical survey conducted in 2015, there were still 79 % of businesses which used sprinklers for irrigation, whereas only 32 % used (also) water-saving drip irrigation¹¹⁵. This is why funding for irrigation technology from sources such as agricultural investment funding programmes is nowadays granted typically only in those cases where such investments are linked to relevant water- (and energy-) saving purposes. In order to practise water-saving irrigation, it is furthermore crucial to ensure the optimum timing and to use the optimum amount of water: Irrigation in the mornings and evenings is distinctly more efficient in order to minimise water loss due to evaporation.

From an ecological point of view, irrigation cannot be judged to be of equal value in all regions or situations. Adverse effects of irrigation can manifest in terms of lowering the groundwater level and changing the soil’s mineral balance. So far, the proportion of irrigated arable land is still low in Germany (amounting to 3 % in 2019). And also the proportion of agricultural use of water for irrigation purposes was low – in 2019 amounting to 2.3 % of total water abstraction, albeit already higher than in 2016¹¹⁶. Nevertheless, it is likely that the actual volume of abstracted water is underestimated. It must be said that sustained impacts on the water regime in regional irrigation ‘hotspots’ or conflicts of use cannot be ruled out. In north-eastern Lower Saxony, the limitations placed on businesses within the framework of water allocations – in accordance with permission required under water-related law – might be a limiting factor for any further expansion of irrigation. During the 2018 drought, it is estimated that some of these water allocations were indeed exceeded. It is therefore essential to increase water use efficiency. Opportunities include the increase in humus content, furthering deep root penetration, optimal tillage, creative crop rotation, choice of suitable species and varieties, adapting planting densities, irrigation control and adapting irrigation technology. Furthermore, there are options available for seasonal water storage.

^{115 - StBA – Statistisches Bundesamt 2017: Land- und Forstwirtschaft, Fischerei – Bewässerung in landwirtschaftlichen Betrieben / Agrarstrukturerhebung – 2016. Wiesbaden, 38 pp. https://www.destatis.de/DE/Themen/Branchen-Unternehmen/Landwirtschaft-Forstwirtschaft-Fischerei/Landwirtschaftliche-Betriebe/Publikationen/Downloads-Landwirtschaftliche-Betriebe/betriebe-bewaesserung-5411205169004.pdf.}

^{116 - StBA – Statistisches Bundesamt 2022: Umwelt –Nichtöffentliche Wasserversorgung und nichtöffentliche Abwasserentsorgung – Fachserie 19 Reihe 2.2 – 2019. https://www.destatis.de/DE/Themen/Gesellschaft-Umwelt/Umwelt/Wasserwirtschaft/_inhalt.html#_qnan5ycnj.}