Efficient Late-Season Irrigation for Optimal Crop Yields

The end of the growing season is crucial for farmers, especially when it comes to irrigation. This period requires a balance, keeping crops sufficiently watered for optimal yields while also depleting stored soil water.

A recommendation from the University of Nebraska Extension suggests that starting from August and extending into September, crops should be allowed to utilize more stored soil water. By the time crops mature in September, the stored soil water content should be lower than it was in August. They advise reducing soil water levels from 50% to 40% after crops reach certain stages.

Farmers often miss the opportunity to harvest off-season rain storage by ending their seasons with overly wet soil. This excessive watering can lead to over-irrigation, as seen in 2017 when 72% of fields were over-irrigated late in the season.

Why does this over-irrigation happen? Habits could be to blame. Farmers set irrigation routines during July, the peak of plant transpiration. But as daylight shortens and temperatures cool in late summer, many continue this high-level irrigation. This despite the drop in water needs for crops like corn and soybeans as they mature.

Judgmentary irrigation can save money, improve harvesting conditions, allow off-season rain storage, and reduce nutrient leaching. For example, a silt loam soil field at full capacity can capture 5.5 inches of off-season rain, resulting in a potential savings of around $7,200, including nutrient retention.

In Nebraska, the off-season from October to May typically sees enough precipitation to replenish soil moisture. By optimizing irrigation, farmers can benefit from this rain, improve harvest conditions, and guard against multi-year droughts. Precise water management can reduce nitrate losses, safeguarding groundwater.

Water needs as the season ends depend on the crop and its growth stage. For example, corn requires five inches of water to mature, while soybean maturity depends on day length. Tools like ET gages and soil water sensors can help farmers accurately gauge water needs, ensuring efficient irrigation and maximum yields.

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