Direct and residual effect of fertilizer phosphorus on barley in Cyprus
1988
Orphanos, P.I. (Agricultural Research Inst., Nicosia (Cyprus))
In a long-term experiment, barley was grown in seven successive seasons (1980-87) in the same field, the soil of which was a sandy loam containing 20% CaCO3 and NaHCO3-extractable P equal to 4 ppm. For the first five seasons, treatments were 0, 30, or 60 kg P/ha, broadcast as triple superphosphate and tine-cultivated into the soil prior to sowing; in the last two seasons P was not applied so that the effect of residual P could be assessed. The crop was harvested for hay in mid-April at the milk stage of the grain. Rainfall was mostly less than 300 mm, which is the water requirement of the crop. As a result the crop suffered various degrees of water stress in the different growing seasons. Fertilizer P increased yield significantly in all seasons but one, in which there was relatively high rainfall in November, December, and January. Application of 30 kg P/ha was sufficient for maximum yield and increased NaHCO3-extractable P to 15 ppm after two growing seasons. The difference between the amount of P removed by the unfertilized and the fertilized crop plus the increase in NaHCO3-extractable soil P accounted for about 30% of the fertilizer P applied in agreement with established norms. 8 ppm NaHCO3-extractable soil P in the plow layer was sufficient for maximum yield
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