Citrus nursery production in soilless culture

Abstract

The Brazilian citrus industry represents an important economical activity in the country. It engages the work of several business components within the farm and along the internal and export markets. The increase and mostly the maintenance of citrus groves in the field require the production of a large number of nursery plants. Since January of 2003, the citrus nursery production must be done under protected cultivation in order to minimize diseases dissemination as citrus variegated chlorosis and greening. Today, the total area of protected citrus nursery production is estimated in 150 hectares, producing around 15 million plants per year. Together with the use of closed protected environment there is a need for substrates use instead of soil. Different types of substrates have been used such as composted pine bark and coconut fiber. In addition to this, the volume of substrate in bags varies from 4 to 7 L and so, the nutrient reserve in this condition is not sufficient for the plant requirement. The use of fertigation is the only way to apply water and nutrients during all stages of citrus plant growth. Because of the type of nurseries and horticultural characteristics of rootstocks and scions there is a need to develop guidelines for best nutrient management of these plants. There are three important phases of citrus nursery production: rootstocks seedling growth in boxes or in plastic tubes of 50 ml until the height of 20 to 30 cm (120 to 160 days after planting), rootstock plant growth in bags until the budding stage (50 to 120 days after the transplanting), and the scion growth until the plant is ready for field transplanting (90 to 150 days after the budding). For all phases, a complete nutrient solution has been suggested composed of (mg/L): N (200), P (30), K (180), Ca (150), Mg (30), S (40), B (0.3), Cu (0.5), Fe (2.0), Mn (0.5), Zn (0.3), and Mo (0.1) with an EC around 2.0 to 2.5 dS/m. The usual management of the nutrient levels in the substrates is by the "pour-thru" technique and by chemical analysis of the substrate or of the drained substrate solution after the pour-thru. Some variation on the nutrient solution composition is done according to the substrate, water, rootstock, scion and season.