D. Alt et al., Long-term trial with increasing amounts of phosphorus, potassium and magnesium applied to vegetable crops, ACTA HORT, (506), 1999, pp. 29-36
The effects of different rates of P, K and Mg fertilizer on the yield and n
utrient removals for selected vegetable crops, and on the nutrient contents
of the soil have been analysed for the last nineteen harvests of a forty y
ear fertilizer trial at Osnabruck in Germany. It was concluded that:
1. The effects of phosphorus were generally small, with yields without P fe
rtiliser averaging about 90 % Of the maximum.
Responses to potassium were much larger, with unfertilised treatments givin
g an average of only 74 % of maximum yield.
3. Mg had no effect on yield.
4. Different crops showed different responses to P and K. Lettuce, onion, f
ennel, and bean showed strong responses to P, whereas spinach and celery we
re more responsive to K. In most cases cabbage showed only weak responses t
o P and K.
5. Annual amounts of nutrients removed by the edible plant parts were on av
erage 22 kg P ha(-1), 190 kg K ha(-1) and 10 kg Mg ha(-1).
6. Average nutrient removals in edible plant parts were 0.4 kg P t(-1), 3.7
kg K t(-1) and 0.22 kg Mg t(-1).
7. On average, soil nutrient contents of between 8 and 12 mg P per 100 g so
il, 8 and 16 mg K per 100 g soil and 5 mg Mg per 100 g soil can be regarded
as sufficient for maximum yield.
8. Important factors in deciding the fertiliser requirements of vegetable c
rops should include soil analysis, nutrient removal by edible plant parts,
nutrient supply from organic amendments and the specific responses of diffe
rent vegetable crops to P and K. Existing computer programs for predicting
nutrient requirements can be used to advise on scientifically based fertili
zer strategies at a farm level.