CNMI farmers lectured on proper fertilizer use
Northern Marianas College – CNMI Cooperative Research, Extension and Education Service’s soil scientist Steven Hill is providing recommendations on the amounts of fertilizer required for profitable production of vegetable and fruit crops in the CNMI.
Two main reasons that farmers should learn about fertilizers are overuse and under-use. “Overuse” refers to applying too much fertilizer, or to applying the wrong fertilizer. Applying a fertilizer that is not needed will not make plants healthier and is a pure waste of money.
Many farmers overuse fertilizers and as a consequence spend too much money on them, which reduces their profits. Overuse of fertilizers also increases the chance of environmental contamination with fertilizers leaching into the ground water or running off onto the beaches after heavy rains.
“Under-use” means the soil lacks certain fertilizers or there basically is not enough fertilizers mixed into the soil. Some farmers under-use fertilizers and, as a result, harvest low yields of vegetables and fruits and experience low profits.
According to Mr. Hill, “each field can differ in the amounts of fertilizer required depending on the type of soil, the history of the field management, availability of irrigation and the type of crop that is to be grown.”
In order for an accurate recommendation on the amount and type of fertilizer needed for the field, soil samples have to be taken. Tests on the soil samples are taken by NMC-CNMI CREES staff and then sent to the University of Guam for analysis and proper soil/fertilizer breakdown.
Mr. Hill provides fertilizer recommendations free of charge based on the test results and the farmer’s plan on which crops he/she will grow. The cost varies depending on what kinds and how many fertilizers are being tested for.
The basic analysis costs $10 at the University of Guam testing laboratory, with shipping charges for the soil sample to be added onto that.
A copy of the laboratory’s quarantine permit must be taped onto the package to ensure the sample is not confiscated before reaching the laboratory. This can be obtained by contacting the NMC-CNMI CREES office on Saipan, Tinian, or Rota.
Actual soil tests within the last two years have been conducted on about 40 farms on Saipan, about five farms on Tinian, and about 15 farms on Rota. These tests have already contributed to our knowledge of fertilizer requirements throughout the CNMI.
As a general rule of thumb, soils on Tinian have excellent fertilizer reserves and only require nitrogen for good yields. Urea is the cheapest form of nitrogen available. Soils on Saipan and Rota may not have enough phosphorus if they have been cultivated for a long time.
Triple Super Phosphate (TSP) is the cheapest form of phosphorus available. A soil sample should definitely be taken before applying TSP to avoid wasting money by adding too much or too little.
On all three islands, Mr. Hill is concerned about iron deficiency in the soil, but he does not have sufficient information to make firm recommendations about iron fertilizer use at this time.
Iron sulfate and other iron fertilizers are hard to find, but they can be imported at a reasonable cost. Anyone interested in trying these should contact NMC-CNMI CREES for further information.
Newly cleared fields that have been in grass, weeds, or tangan-tangan will have a lot of nitrogen, and urea may not be needed for healthy crops. After a few years of planting on the same farm, some urea should be added to most crops to ensure good production.
Crops that should not have urea added to them include beans, peas, tapioca, and sweet potato. In coming weeks, further information will be posted about fertilizers, including organic fertilizers, an important subject that was not discussed in this article.
