While leaves pale between the veins with the veins still green (interveinal chlorosis) can indicate magnesium deficiency, it's not the only possibility. Pale between the veins with the veins still green could also indicate iron or manganese deficiency. The difference would be in the first leaves that are affected. If it is the oldest leaves it is more likely to be magnesium deficiency. If it is the youngest leaves that are affected first, it is most likely iron and/or manganese deficiency. Magnesium deficiency is more likely on an acidic soil, while iron or manganese deficiency are more likely with a soil pH higher than around 6.5. Not all daylilies are equally fussy about soil pH so you can have some affected while others are not.
The Daylily Dictionary pictures of interveinal chlorosis shown in these links was caused by manganese deficiency (not to be confused with magnesium deficiency) induced by liming when the soil didn't need it (the area had been used for wood ashes whereas the rest of the garden had tested with a lower pH). The culprit nutrient was determined by leaf tissue testing and a soil test. There was plenty of manganese in the soil but the pH prevented the plants from using it. The remedy was to lower the pH back down with sulfur because that allows iron and manganese to become available to the plants again - most of the time, and as in this case, they are not actually at low levels in the soil but "blocked" by the soil pH getting too high:
http://www.daylilies.org/ahs_d...
http://www.daylilies.org/ahs_d...
I notice, Greg, that you applied potassium and phosphorous along with the nitrogen. Deficiency of both those were shown to cause short scapes in the study reported in the AHS 2002 Handbook.
Egg shells are primarily calcium carbonate (lime) so if ground enough and applied in sufficient amounts they add calcium and can also change the pH according to studies.
http://www.agronext.iastate.ed...
http://www.aces.edu/timelyinfo...
Also this article:
http://www.gardenmyths.com/egg...
The key, though, is that to do either they must be finely ground and not crushed (and a large enough amount applied, of course).
Back to yellowing foliage - an important diagnostic factor there is that with magnesium, iron and manganese deficiencies the veins remain green while the areas between are pale. If the yellowing includes the veins, it is more likely to be nitrogen or sulfur deficiency. Nitrogen is the nutrient most often in short supply (it's the only one that doesn't naturally originate from minerals in the soil). Nitrogen deficiency typically affects the oldest leaves first, i.e. in daylilies it would be the lowest/outside ones in a fan that would turn yellow. Interestingly, though, nitrogen deficiency was not reported to cause short scapes in the study reported in the AHS 2002 Handbook.
I would be very careful about applying calcium/liming materials to daylilies unless someone knows for sure their soil is lacking or the pH is more than a little acidic. Soil testing is always going to be the best bet because undoing something can be harder then doing it
At the very least always get a soil pH test before applying any liming material (or sulfur) because the pH of the soil determines the availability of nutrients to the plant.
