EFFECTS OF SOIL PHOSPHATE LEVEL AND PHOSPHATE APPLICATION RATE ON THE YIELDS OF FOUR FIELD VEGETABLES

In the Netherlands, the phosphate (P) fertiliser recommendations for field vegetables are much higher than the phosphate removed (P-removal) by the marketable crop.
As a result soils may become saturated with phosphate.
This increases the risk of phosphate emission to ground- and surfacewater.
To meet both agricultural and environmental requirements of fertiliser use, field trials were conducted to assess whether it is possible to reduce the amount of phosphate fertiliser.
From 1996 until 1999 field trials were carried out, using leek, carrot, cauliflower and head lettuce as pilot crops.
On both sand and clay, trials were conducted at different levels of water-soluble (Pw) phosphate of the top soil-layer using different phosphate application rates.
For each crop the marketable yield was determined.
Thereafter, the yield (y) response to the total amount of available phosphate (applied phosphate (P-rate) in combination with the available P in the soil (soil-P)) was fitted using the equation:

(1)  y  =  (1-e^{*(P_rate+*soil_p)})+

Assumed is that is normally distributed with expectation zero.
Alpha () is the maximum yield.
Gamma () describes the decrease in yield with decreasing total available phosphate and phi () relates the total available phosphate to that in the top soil-layer.
Furthermore, for each P-soil level the economically optimum P-application rate was determined.

The results indicate that in most pilot crops it is possible to adjust the recommended amount of phosphate without reducing the yield.

Workshop Towards and Ecologically Sound Fertilisation in Field Vegetable Production

C. van Wijk, J. Neuvel, W. van den Berg

Carrot, cauliflower, lettuce, leek, P-application, P-level, P-rate, phosphate

https://doi.org/10.17660/ActaHortic.2002.571.27