Deliverable 2. Fertigation recipes for selected crops in the Mediterranean region (CYPRUS)

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Fertigation increases efficient use of water and fertilizers, produces higher yields, improves quality of the production and protects environment. To ensure uniform distribution of water and fertilizers, the irrigation system must be properly designed and operated. The choice of suitable fertilizers is also very important and must be based on several factors like nutrient form, purity, solubility and cost.

 To implement a fertigation program, particularly under intensive greenhouse production, good knowledge is required of water and nutrient requirements over the growing season. The fertigation model developed to be used at farmers level concerns drip-irrigated greenhouse tomato, pepper, cucumber and melon. It takes into account the amount of nutrients which may be available to the crop from soil and calculates for a target yield the quantities of N, P and K fertilizers which may be supplied through the irrigation stream over the growing season.

 Starting with soil mass occupied by roots (M, tons) it is estimated from the area of the plantation (A, m²), root depth (D, m), soil volume occupied by roots (V, %) and soil bulk density (Bd, tons/ m³) with the following formula:

A x D x V x Bd

M =  --------------------------

                                 100

 Concerning the amount of soil available nutrient (SAN, kg/ha) it is estimated from soil mass and the available value for each nutrient (AV, g/ton), as determined by chemical analysis on representative soil samples, according to:

  M x AV

SAN =  ------------

   1000

 The amount of nutrient required to be supplied by fertilizers (NS, kg/ha) is finally estimated from nutrient requirement of the crop (NR, kg/ha), soil available nutrient, safety margin (SM, kg/ha) which is the amount of soil available nutrient to be reserved in soil (for P or K) and nutrient uptake efficiency (Ue, fraction) which depends on the irrigation system and soil type:

NR – SAN + SM

NS =  -------------------------

Ue

 The amount of nutrient estimated with the above formula over a certain period, is combined with the respective crop water requirement in order to arrive at nutrient concentration in the irrigation water. The model calculates N, P and K concentration for both the preflowering and fruiting cycles. Taking into consideration the fertigator and irrigation system discharges, as well as the selected combination of fertilizers, nutrient concentrations in the irrigation water are finally converted to concentrations of fertilizers in the stock solution tank.