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Posted on 8:16 PM by Wanto and filed under
By John Simpson
Potassium is best applied in the form of sulphate of potash and phosphorus in the form of superphosphates of lime or as bone meal. Nitrogen can be given in a number of forms, some quick acting, e.g. sulphate of ammonia, some slow acting, e.g. hoof and horn meal.
On the whole it is better to apply these staple requirements in the form of a complete fertiliser, that is one that contains all three, rather than to attempt to diagnose which is the missing element, as it will be fairly obvious that the symptoms tend to overlap, and it is not always easy to say exactly what is wrong.
Usually even if a reasonably well balanced fertiliser is used, it will be found with dahlias that there is not sufficient potash for their requirements, so that it is as well to give an additional dressing of sulphate of potash at the rate of 2 ounces to the square yard, at least twice during the growing season, say in late June and early August, particularly if the plants are lush and soft, and the blooms tend to scorch or wilt in the sun.
If despite using this feed the colour is still not good, try adding a little sulphate of iron to the mixture, or give a supplementary feed with either this chemical or sequestrene of iron.
Incidentally when testing the soil for pII value, it is advisable to make tests in different parts of the dahlia plot, as soil values often vary quite considerably within a limited area. Suspected iron deficiency can be rectified by adding sulphate of iron, at the rate of one ounce per square yard, or by iron sequestrene at the rate recommended by the makers. Magnesium can he replaced by using commercial Epsom salts (magnesium sulphate) at one ounce to the gallon of water, giving each plant about a quarter of a gallon of the solution.
This is a fairly slow acting fertiliser, but some part of it becomes available reasonably quickly, about two to three weeks after application so that it is best to anticipate the plant's needs if possible. This is not so impossible as it sounds, as a somewhat soft plant soon indicates its softness by the way its leaves tend to droop in the sun following a heavy shower of rain. As an alternative to using ready made fertilisers many growers make their own fertilisers, but although somewhat cheaper it is much easier to rely upon the commercial articles as these are usually well compounded and extremely wisely balanced. Quite a good one can he compounded from 8 parts dried blood or sulphate of ammonia, 8 parts superphosphate of lime, 4 parts sulphate of potash, 2 parts commercial Epsom salts, 1 part sulphate of iron, all parts by weight.
On the whole it is better to apply these staple requirements in the form of a complete fertiliser, that is one that contains all three, rather than to attempt to diagnose which is the missing element, as it will be fairly obvious that the symptoms tend to overlap, and it is not always easy to say exactly what is wrong.
Usually even if a reasonably well balanced fertiliser is used, it will be found with dahlias that there is not sufficient potash for their requirements, so that it is as well to give an additional dressing of sulphate of potash at the rate of 2 ounces to the square yard, at least twice during the growing season, say in late June and early August, particularly if the plants are lush and soft, and the blooms tend to scorch or wilt in the sun.
If despite using this feed the colour is still not good, try adding a little sulphate of iron to the mixture, or give a supplementary feed with either this chemical or sequestrene of iron.
Incidentally when testing the soil for pII value, it is advisable to make tests in different parts of the dahlia plot, as soil values often vary quite considerably within a limited area. Suspected iron deficiency can be rectified by adding sulphate of iron, at the rate of one ounce per square yard, or by iron sequestrene at the rate recommended by the makers. Magnesium can he replaced by using commercial Epsom salts (magnesium sulphate) at one ounce to the gallon of water, giving each plant about a quarter of a gallon of the solution.
This is a fairly slow acting fertiliser, but some part of it becomes available reasonably quickly, about two to three weeks after application so that it is best to anticipate the plant's needs if possible. This is not so impossible as it sounds, as a somewhat soft plant soon indicates its softness by the way its leaves tend to droop in the sun following a heavy shower of rain. As an alternative to using ready made fertilisers many growers make their own fertilisers, but although somewhat cheaper it is much easier to rely upon the commercial articles as these are usually well compounded and extremely wisely balanced. Quite a good one can he compounded from 8 parts dried blood or sulphate of ammonia, 8 parts superphosphate of lime, 4 parts sulphate of potash, 2 parts commercial Epsom salts, 1 part sulphate of iron, all parts by weight.
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