Progress in Mineral Nutrition and Nutrient Management for Vegetable Crops in the Last 25 Years

Abstract

K. Early manufactured fertilizers were mostly solid materials, but in the middle part of the 20th century, liquid versions of fertilizer materials, particularly N, became available and their use increased rapidly in the latter quarter of the 20th century. The liquid materials, containing N and P, were very useful as vegetable transplant starter fertilizers, and the liquid N materials were used as easily-applied sidedress fertilizers. During the last 25 years, many advances have been made in the formulation of mixed-nutrient liquid fertilizers, many containing most of the essential nutrients for plant growth. The major factors driving the development of liquid fertilizers include the ease and uniformity of application, the advent of drip irrigation and fertigation (the application of nutrients with the irrigation system), and the development of modern hydroponic and greenhouse vegetable production systems. Drip irrigation and greenhouse vegetable production will be discussed later in this paper. FERTILIZER SOURCES. Over the last 25 years there were numerous researchers evaluating fertilizer sources for specific nutrients for vegetable crops, for example the work by Locascio et al. ( 1981) and Locascio and Martin (1985). Much of the work focused on N fertilizers, but there also has been considerable work on P, K, and micronutrient sources. The researchers had to account for the possibility of responses to associated nutrients supplied with the nutrient of interest. For example, potential crop responses to S, Ca, or K had to be considered in N-source studies involving CaNO 3 , NH 4 SO 4 , and KNO 3 . In most studies with most vegetables, there were negligible crop responses to N source so that most sources can be recommended for vegetable culture and the choice may depend on cost. CONTROLLED-RELEASE FERTILIZERS AND NITRIFICATION INHIBITORS.