EFFET DE LA FERTILISATION PHOSPHATEE SUR LA POMME DE TERRE EN RELATION AVEC L’ANALYSE DU SOL ET LA SOURCE DE PHOSPHORE UTILISEE

Abstract

The effect of phosphorus fertilization on potato yields (Solanum tuberosum L.) was studied on 24 experimental sites varying from 44 to 1000 kg/ha of soil test P. The respective relative yields (yield with P fertilizer/maximum yield with P fertilizer x 100) varied from 20.3 to 100%. The Mitscherlich equation was used to relate relative yields to soil test P. According to their soil test value, the soils were partitioned in three classes by the Cate-Nelson method to establish poor (300 kg/ha of available P or less), medium (301–400 kg/ha P) and rich 401 kg/ha P or more) soil fertility classes. It was found that 94 kg/ha fertilizer P was necessary for maximum yields with an increase of 10% or greater on poor soils. On medium and rich soils, the requirement was 50 kg P/ha for a yield increase of 1–10%. Below a 1% increase, the P application should be lowered. At high rates diammonium phosphate (DAP) has been found to give tuber yield equal to those of superphosphates. On the other hand, at low rates, DAP application was more effective. DAP induced a higher mid-season P concentration in the petiole tissue Acidification by superphosphates increased aluminum, iron and manganese availability in the soil and reduced P solubility in the band area, in contrast to DAP. Key words: Potato, soil test phosphorus, source of phosphorus fertilizer, phosphorus fertilization, superphosphate, ammonium phosphate