Abstract

Nitrogen, phosphorus and potassium are the main components determining yield and quality of intensive agricultural production particularly at undercover production, however; excessive fertilization has some environmental and economical consequences. The aim of this study was to investigate surplus amount of fertilizers at the harvest stage of the greenhouse soils in Antalya Province. Therefore, soil samples were collected from 57 representative greenhouses to determine their mineral nitrogen, available phosphorus and potassium along with organic matter contents. The results revealed that soil from 30% of greenhouses had nitrate values of 30 to 35 kg da^-1. Ammonium values were considerably low compared to nitrate values; the highest ammonium value was nearly 6 to 7 times lower than the highest nitrate. The highest distribution according to ammonium content was found as 46% with the value of <1 kg da^-1. This result indicates that nitrate is the more preferred mineral nitrogen source than ammonium in the study area. One tenth of greenhouses had low P content, whereas the rest of the greenhouses had sufficient amount of P. Potassium content of the analyzed soil samples are classified either as "very low" or "low". On the other hand, over the half of the greenhouses have sufficient or even higher amount of organic matter. This study clearly shows that the greenhouses usually contain sufficient quantities of macro nutrients even at the harvest stage of the plants. This implies that the farmers may postpone the fertilization for a longer time if they consider the nutrient budget and status of soil nutrients. However, farmers in Turkey are not generally considering nutrients existence in the soil before applying fertilizer.

Key words: Greenhouse, mineral nitrogen, available phosphorus, available potassium, Antalya.