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Changes in farming practices can yield big savings in water use

Contrary to popular belief, there is large potential to cut water use in California agriculture without fallowing fields. - Photo: Canva
Contrary to popular belief, there is large potential to cut water use in California agriculture without fallowing fields. - Photo: Canva

A recent study conducted by researchers at UC Santa Barbara in the United States reveals that variations in farming practices can yield significant water savings, potentially rivalling the impact of switching crops or leaving fields fallow.

Contrary to prevailing assumptions, the study, published in Nature Communications, employs innovative data-driven methodologies to demonstrate ample opportunities for reducing water usage in California’s agricultural sector without resorting to field fallowing. By leveraging remote sensing, big data analytics, and machine learning, the research team assessed water consumption by crops in the Central Valley of the state.

Lead author Anna Boser emphasises that less drastic measures than field fallowing may prove pivotal in addressing California’s water challenges, challenging the notion that substantial changes in land use are necessary.

Crop-specific water usage

Boser’s focus on crop-specific water usage led her to compare transpiration rates between fallowed and active fields throughout the Central Valley. Subtracting evapotranspiration (ET) in fallow fields from total evapotranspiration yields the amount of water that crops are actually consuming.

The research found that crop type alone accounted for only 34% of the variation in water consumption, suggesting overlooked opportunities for water conservation. She investigated the model, controlling for factors like location, topography, local climate, soil quality and orchard age.

Irrigation efficiency across the counties of the Central Valley. – Image: UC Santa Barbara
Irrigation efficiency across the counties of the Central Valley. – Image: UC Santa Barbara

Differences in farming practices

Ultimately, a significant reduction of 10% in crop transpiration could be achieved if the top 50% of water users adjusted their consumption to match that of their median-consuming counterparts. Boser attributes these potential savings to differences in farming practices.

Similarly, if this same group of farmers transitioned to cultivating median water-intensive crops for their respective regions, agricultural evapotranspiration would decline by 10%. Such variations underscore the wide-ranging differences in water consumption among various crop types.

The study suggests that removing the top 5% of the most water-hungry fields from production could also result in a 10% decrease in agricultural evapotranspiration. This highlights the substantial impact that addressing inefficiencies in farming practices can have, potentially rivalling the water-saving benefits of switching crop or fallowing fields.

However, fallowing remains the most efficient method for reducing agricultural evapotranspiration. The researchers note that leaving just 5% of land fallow could yield a significant 9.3% reduction in water consumption, comparable to the savings achieved through crop switching and within-crop adjustments, which by definition affect up to 50% of cultivated lands.

Variations in annual agricultural evapotranspiration (ET) across and within crop groups. – Image: UC Santa Barbara
Variations in annual agricultural evapotranspiration (ET) across and within crop groups. – Image: UC Santa Barbara

Changing irrigation practices

The authors aim to figure out what farming practices are responsible for 10% variances in crop water usage. Some notable examples include mulching, no-till planting, the adoption of drought-tolerant varieties, and deficit irrigation, a method where growers intentionally provide less water than the crop theoretically consumes. Deficit irrigation has already shown promising outcomes in viticulture, where vintners have observed enhancements in wine quality.

Optimising irrigation practices presents another avenue for reducing water consumption. Irrigation efficiency accounts for the fraction of water a farm uses that actually gets consumed by crops. Inefficiencies include issues like leakage, weed proliferation, and evaporation during transportation and in the field. However, these factors were not within the scope of Boser’s model, which solely focuses on crop transpiration. Notably, these inefficiencies occur even before water reaches the plants.

Reaching the roots

According to Boser, approximately 60% of the water utilised by a farm ultimately reaches the roots of its crops. She emphasises the considerable potential for improvement in this domain, though the attainable level of efficiency remains uncertain. “Irrigation efficiency is actually quite poorly understood”, she says.

The research team aims to pinpoint the root causes of irrigation inefficiencies, quantify the effectiveness of various irrigation methods, and explore how climate and geography effects irrigation efficiency. All this will require collecting empirical data.

Overall, the findings underscore the potential for fine-tuning farming practices to achieve substantial water savings, offering a more nuanced approach to water management in California’s agricultural landscape.

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Groeneveld
René Groeneveld Correspondent for Australia





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