Jay said:

I have horses and an abundant supply of manure. I hot compost the
manure, turning frequently, until it is no longer heating.

My question is, is this a good source of fertilizer, (nitrogen, et.
al.), for my veggie garden? I'm fairly new to gardening but my plants
look rather weak and yellow. I started the garden with lots of
compost but didn't add any other fertilizer. Is compost enough or
not?

Compost is very, very important, #1 - #5 on the Most Important Thing I Can Do
for My Veggie Garden list.

But it won't neccessarily add everything you need. You may, especially in
a very rainy season*, need to add some other source of nitrogen. Your soil
might have other shortages that compost alone won't correct. That's what
a soil test will help you find out. Ideally, this will test for P, K, Ca, and a few
of the other 'major minor' nutrients. (In the US, these can usually be had for
a reasonablel fee through your county Cooperative Extension Service.)

Organic sources of supplemental nitrogen include blood meal, alfalfa meal
or pellets (my favorite), fish meal and certain fresh manures (but these I suggest
are best added to batches of compost). Foliar sprays with fish emulsion, compost
tea, alfalfa tea, or (my favorite) seaweed are extremely valuable

Shortages of some nutrients can be put into your 'soil bank' through the use of
natural mineral materials which will become available slowly over years.

If you need Calcium, you can add ground limestone (make that dolomitic
limestone if you are also short of magnesium) but in high pH soil, add
gypsum instead, which won't raise the pH any higher.

Greensand is a source many micronutrients, and one major (K, potassium)
that are available very, very slowly.

Ground rock phosphate will add P (slowly rather than quickly).


*Lots of plants looking a bit nitrogen starved around here, due to so much rain.
But at least they aren't swamped, what with the sandy soil I have.
--
Pat in Plymouth MI ('someplace.net' is comcast)

Any technology distinguishable from magic is insufficiently advanced.
(attributed to Don Marti)