If you eat less, you’ll eventually lose weight. The same is true for rice plants and fertility (their food). We all want to make more crop while spending less money, but we don’t need to spend less wisely.
First, I’m still surprised at the number of growers who call that don’t conduct standard soil testing on their fields. It’s difficult (impossible?) to know if you’re doing the right thing if you don’t know where you stand.
Soil test, even if it means the fertilizer will have to go out by air or ground after the rice is planted.
Contrary to the belief of many, there is not much soil level “build” in our current fertilizer recommendations. Soils falling in the Very Low or Low soil test categories should be fertilized as recommended. Period.
For soils falling around the Medium category, some slight reductions from the recommendations may be possible without any negative impact. This means for phosphorus (P) a reduction of no more than 10% or for potassium (K) a reduction of no more than 20%. Keep in mind these reductions may put you in the “pay for it now versus pay for it later” situation.
Environmental conditions will always be the unknown variable affecting how much of these nutrients are lost or made unavailable, so there is still risk with these reductions.
Zinc (Zn) fertility is a little different animal. Generally, there is no substitute for 10 lbs of Zn applied as zinc sulfate. It’s not cheap, but it’s not really any more expensive than other Zn products, which provide much less Zn and don’t build the soil at all.
In addition, distribution is key because Zn doesn’t move from where it lands. Running 5 pounds of Zn may be adequate in many situations but is difficult to blend and get the desired field distribution.
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So, stick to the soil test recommendations when fertility levels are in the Very Low to Low categories and only consider deviating slightly at higher category levels. Remember that areas in the field may have lower levels, so deficiencies can still show up.
At the end of the day, fields with higher fertility levels will readily benefit from a maintenance rate of 0-30-60 or 0- 45-60 (N-P-K). A rice plant is happiest with a full belly, so feed it.