There isn’t much to say regarding the wheat crop right now but to wait so let’s go in a different direction this week. First, the Crop Protection class at the college toured the area south of the college this past Wednesday travelling as far south as the Hudson area. Normally they can examine wheat, alfalfa, and newly emerged corn. Since the weather went south pretty quickly, the tour was a bit abbreviated. It’s safe to assume they didn’t find any corn emerged or even germinated. The alfalfa seemed to be doing alright and was recovering well from the freezing weather. On the plus side, the cold weather had greatly diminished insect pressure. When splitting open wheat stems, they only found a few with obviously freeze-damaged heads. Naturally, the wheat will be short and leaf damage was visible but little in the way of insect or disease pressure was visible. The crop which appeared to suffer the most (damage that won’t bother most wheat producers) was rye. Rye fields in the area were heading out and damage to the head was apparent.
The “Law of the Minimum”, proposed by Sprengel and popularized by German Chemist Justus von Liebig is a cornerstone of modern crop production and fertilizer science. The law simple states “if one of the essential plant nutrients is deficient, plant growth will be poor even when all other essential nutrients are abundant.” In more general terms it means growth is controlled not by the total amount of resources available, but by the scarcest resource or the “limiting factor.” This concept has broad implications for crop production, especially as agriculture intensifies even more in the quest to increase productivity per acre to meet an ever increasing demand for food, fiber, and fuel. So what does it mean for crop production?
· There are 16 essential nutrients for crop growth. They are group by the relative amount the plant needs with nine macronutrients and seven micronutrients. While the micronutrients (iron, zinc, etc.) are needed in minute amounts compared to what we think of as fertilizers (nitrogen - N, phosphorus - P, potassium - K, etc.). However, if these micronutrients aren’t available in adequate amounts, they will limit yields even if adequate amounts of the macronutrients are present.
· Crop yields have increased dramatically over the last fifty years so we are removing ever increasing amounts of nutrients. Producers have paid attention to the big three (N-P-K) but increasingly, especially on lighter soils or soils low in organic matter, nutrients like sulfur, chloride, and zinc are becoming deficient and limiting yields.
· What all this means is an increasing need for more intensive soil and plant tissue testing to identify and address nutrient deficiencies that previously were rare. While this costs time and money, the money lost by not investing in a comprehensive nutrient management program is greater.
· Finally, paying attention to the Law of the Minimum concept can save money since often these problems are addressed by applying more of the traditional nutrients which doesn’t correct the problem.