Water Conservation Is Paramount

Heading into summer we are already drier than normal, so it’s necessary to manage water judiciously for the health of waterways, ecosystems and economics. Its efficient use is also an important element of sustainable agriculture.

Long term rainfall for the Hamilton Basin (Ruakura) is showing a significant dominance of drier than median years since 1980. Twelve of the last 20 years have been significantly drier than average, with 2019 the second driest year on record, while only three have been significantly wetter than average.

With summer upon us it seems timely to revisit the lessons learnt from past droughts so the farming industry and support services can collectively get through the current situation and recover when conditions improve.

Water is lost from the soil by evaporation from the soil surface and by transpiration from the leaves of plants. The combination of these two factors is called evapotranspiration. Water is also lost as it drains through the soil beyond the reach of plant roots. Soil moisture depends on the balance between the water gained from rainfall and the moisture lost through evapotranspiration. The intensity of the rainfall, the number of rainfall events, temperature, sunshine, wind and the amount of water vapour already in the air are all factors that can affect this balance.

There has been growing awareness that our water resources are limited and there are multiple demands on this resource. We need to think in terms of sustainability of the recovery of farming businesses from droughts.

Water harvesting and small-storage technologies are key water-related interventions with the potential to contribute water for domestic use, livestock, fodder and pasture/crop production. If farmers and landowners are considering water storage, please first talk to Waikato Regional Council for further guidance.

There are also a few management practices that farmers can follow to help mitigate the impact of a prolonged dry spell.

With stock welfare a critical issue for many farmers due to feed shortage, grazing management is very important. Most farmers are trying to protect their capital stock. Farmers need to think in terms of sustainability – recovery of the farm business from drought – and be looking at having a good drought management plan.

Farmers with irrigation consents may note that water use efficiency is drastically reduced by irrigation systems with low inherent irrigation application efficiencies or by sub-optimal irrigator operating practices. By paying attention to systems, farmers can improve their irrigation practices and the amount of pasture produced per unit of water applied.

Efficiency can be boosted by applying water more evenly or by differential irrigation over areas of different soil type – if applications are more uneven than the system design specifications, modifications to the system may be needed to rectify the problem.

It’s important that water or effluent is not being applied faster than the soil can absorb to avoid ponding, runoff and excessive drainage, and to enable more even soil moisture levels across the paddock.

Farmers could also consider pasture types or species that have inherently higher water use efficiencies than ryegrass and white clover. Lucerne, for example, is well known for continued growth when moisture stress stops ryegrass and clover growth. Other pasture types, such as tall fescue, are also potentially more drought tolerant. The important point to be considered here is the productivity of these alternative species under commercial situations.

Of late, a phenomenon called ‘hydrophobicity’ is seen during drought situations. It’s an obstruction to normal soil water relationships and the phenomenon has significant implications for water storage in soil. It leads to pastures failing to respond to autumn rains, and delayed pasture recovery especially after drought and the subsequent constraints to winter production. Moreover, it has an adverse effect on pasture persistence and hastens pasture reversion.

• For further information, please call Bala Tikkisetty, Sustainable Agriculture Advisor Technical, on 0800 800 401.

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