I have been growing a Noni Plant from its seed. (It took about 6 months before sprout of tree came up from the soil) In August 2012, I then transplanted it after it outgrew the smallest pot and put it in a pot size of about 24″ in diameter. The tree is growing and is at 48″ tall. I noticed that some of the bark is cracking only on the lower part of the tree and the lower leaves have gone yellow. I live in an apartment. It is dry, but I do put a humidifier on. The Noni Tree sits in the east, getting a lot of morning sun through large windows. I used to water it 2 times a week when it was shorter, but I have been watering it 2 times a day of 2 bottles of 500ml. It is drinking the water up. The yellow leaves stopped for a bit when I increased the water, but are yellowing slowly on the bottom leaves again. There is new growth on the top of the tree and the other leaves are a deep green. There are also buds where flowers will bloom soon. I understand that the cracking of the bark can be caused from a weather change, and may cause problems. I am wondering can I do anything about the yellow leaves. Do I need to add some kind of fertilizer or nutrients to the soil or do I need to transplant.
Congratulations on getting your Noni tree (Morinda citrifolia) to grow so well from seed.
Noni can tolerate a wide range of light levels so your east window is probably fine (the more sun it gets, the more flower and fruit it will produce). If it is setting buds for flowering and producing new leaves it can’t be that unhappy.
From what you have described it sounds like you might be overwatering the plant. Yes, it would rather have moist soil than dry when in a container but you should be able to keep it moist by watering deeply two times a week. Water until some runs through to the pan but be sure not to leave it in standing water. It may have developed root rot from over-watering.
Another requirement you must follow is warm conditions. Noni is a very cold sensitive plant, with a minimum temperature 15C to keep it happy. Below this temperature, leaves get some damage, and below 5C the plant may start wilt, leaves turn brown and drop; it may never recover and die if exposed to temperatures below 2C even for a few hours.
If it is too close to the window it may have experienced very cool nights and this could account for the leaf drop. Now that spring is here you may now be able to give it the warmth is wants.
If it preparing to flower and fruit you should apply a weak mixture of a high-phosphorous fertilizers such as 10-20-20 or 1-45-10 on a weekly basis until the fruit is well established.
Best of luck with your Noni.