Readings taken once per minute provide a rough measure of surface solar radiation. Even with quite a bit of high cloudiness there's enough sunlight to cast a shadow. At day's end, meteorologists tally the minutes as a percentage of possible sunshine. Measurements taken over the last 30 years show that Las Cruces and south-central New Mexico have 84 percent of possible annual sunshine. Soil temperature is key for optimum planting.
Sunshine promotes germination and strengthens tender seedlings.
Converted to heat units and degree days, sunshine affects crop maturity and helps predict when insect populations will peak. Along with wind, sunshine determines the potential evapotranspiration rate used to figure crop water needs and schedule irrigation. Heat-loving crops like cotton crave the sun, first to warm the soil to the 60 degrees required for planting and then to stimulate boll production. Sunlight has built New Mexico's growing nursery industry, which now ranks seventh statewide in cash receipts for agricultural commodities. In southern New Mexico, greenhouses need no artificial light.