A common practice in the U.S. Midwest is to combine the quantities of phosphorus (P) and potassium (K) recommended for both corn and soybean crops into a single application. This biennial application of fertilizer is usually applied after soybean harvest. In a corn/soybean rotation, this results in a “direct” application to corn and a “residual” application to soybeans. Less common, although also studied by scientists, has been a biennial application applied after corn, resulting in a direct application to soybeans and a residual application to corn.
California farmers deal with complex irrigation and fertilization requirements of "specialty" crops within diverse rotations. Some of these so-called specialty crops have a farm value of more than $4 billion per year. These high-value crops demand careful management of both water and nutrients to achieve high yield and consistently high quality.
The 4R program still is and will continue to be a very important program for the crop nutrition industry.
Nitrogen (N) is one of the most widely distributed elements in nature, since it’s the most abundant gas in the atmosphere. While N isn’t found in mineral forms like phosphorus (P) or potassium (K), it’s largely present in organic compounds. Soil-based N undergoes many complex biological transformations that make it challenging to manage.
Potassium nitrate (KNO₃) is a soluble source of two major essential plant nutrients. It’s commonly used as a fertilizer for high-value crops that benefit from nitrate (NO₃-) nutrition and a source of potassium (K+) free of chloride (Cl⁻).
Potassium (K) fertilizer is commonly added to improve the yield and quality of plants growing in soils that are lacking an adequate supply of this essential nutrient. Most fertilizer K comes from ancient salt deposits located throughout the world. The word “potash” is a general term that most frequently refers to potassium chloride (KCl), but it also applies to all other K-containing fertilizers, such as potassium sulfate (K₂SO₄, commonly referred to as sulfate of potash, or SOP).
Liquid fertilizer solutions and fluid fertilizers are popular in many areas because they’re safe to handle, convenient to mix with other nutrients and chemicals, and are easily applied. A solution of urea [CO(NH₂)₂] and ammonium nitrate [NH₄NO₃] containing between 28 and 32 percent nitrogen (N) is the most popular fluid N fertilizer.
Potassium (K) fertilizers are commonly used to overcome plant deficiencies. Where soils cannot supply the amount of K required by crops, farmers must supplement this essential plant nutrient. Potash is a general term used to describe a variety of K-containing agricultural fertilizers. Potassium chloride (KCl), the most commonly used source, is also frequently referred to as muriate of potash, or MOP (muriate is the old name for any chloride-containing salt).
Potassium is always present in minerals as a single-charged cation (K⁺).
Many soils require adding several essential nutrients to alleviate plant deficiencies. Farmers may opt to select a combination of single-nutrient fertilizers or apply a fertilizer that combines several nutrients into each particle. These combination fertilizers (compound or complex) can offer advantages of convenience in the field, economic savings and ease in meeting crop nutritional needs.
Calcium carbonate, the chief component of limestone, is a widely used amendment to neutralize soil acidity and to supply calcium (Ca) for plant nutrition. The term “lime” can refer to several products, but for agricultural use it generally refers to ground limestone.
Langbeinite is a unique source of plant nutrition, since three essential nutrients combine naturally into one mineral. It provides a readily available supply of Potassium (K), Magnesium (Mg) and Sulfur (S) to growing plants.
Despite phosphorus (P) availability from geologic deposits distributed around the globe, widespread P deficiency in soils limits the growth and productivity of plants in many parts of the world. Because of this, growers commonly add this nutrient to their fields to improve crop yield and quality. Polyphosphate is an excellent liquid P fertilizer used to increase agricultural production.