Monday, September 15, 2014

Ways of Adding Phosphorous to the Soil

 Primary nutrients of plants include nitrogen, phosphorus and potassium; they are the ones indicated on each fertilizer package. For example, 5-10-15 printed on the label signifies that the fertilizer contains 5% nitrogen, 10% phosphorus and 15% potassium.

Many soils are deficient in phosphorus, especially those red Hawaiian soils high in iron and aluminum oxides.  When growing vegetables, or any annual crop, phosphorus can be incorporated into the soil before the crop is planted. It can also be incorporated before trees and shrubs are planted. The difficulty comes when attempting to apply a phosphate fertilizer to an established tree or shrub with existing roots already deep in the soil.

In contrast to nitrogen fertilizers which are water soluble and move well in the soil, phosphate fertilizers do not move well. In fact, years after a surface application of a phosphate fertilizer, the majority of the phosphorus will still remain near the soil surface. How then can a phosphate fertilizer be applied and penetrate down to the roots of mature trees?   Here are some better ways of applying a phosphate fertilizer to existing plants

1. Remove a core of soil at the drip line of the tree, at the four corners, 1 – 2 feet deep. Cores can also be removed going around the drip line of the tree in a circular manner. Apply a measured amount of phosphate fertilizer to these holes, either dry and mixed with soil, or in a water solution.  Ammonium polyphosphate is especially good. Admittedly, this involves a good deal of labor when treating many trees. 

2. Similarly, fertilizer spikes, although expensive, can be placed in the ground around the drip line. In both cases, roots will gradually gravitate to the higher nutrient content and flourish.

3.  Foliar applications of a phosphate fertilizers do not work well. Frequent applications of 3-4 times per year, however, can potentially meet the trees requirement.

4. Perhaps the best alternative in improving phosphate availability and movement into the soil is to apply it in its organic form; for example, manures, fish meal and blood meal. Likewise, adding organic mulch is beneficial. As the organic material breaks down, the end product is humus. Humus is loaded with negatively charges sites that are able to hold onto positively charged plant nutrients such as potassium, calcium, magnesium, manganese and iron. Keeping the tree under a bed of mulch will supply a small but constant supply of various essential nutrients.  Roots will eventually grow into the mulched area and proliferate, picking up essential nutrients. In addition, because of the abundance of new surface roots in this area, it now becomes an ideal place to apply a phosphate fertilizer.  

Monday, September 8, 2014

Coconut Palms Bearing Fruit

When can I expect my coconut palms to begin to produce? 

In general, coconut palms will flower in 4 - 6 years. They may not actually produce fruit, however, until they are 6 – 10 years old. And if growing conditions are unfavorable, they may not bear until they reach 15 – 20 years of age. Full production is at 15 -20; they can potentially produce until they are about 80 years old.

Although coconut palms are tolerant of dry soil conditions, for optimum fruit production regular irrigation is recommended, especially during drought conditions. Palms can also endure temporary waterlogged soil conditions. Yet they will decline and even die when exposed to prolonged periods of wet, poorly drained soils. Coconut palms will tolerate saline water and soils, as well as salt spray, but this does not mean they prefer it.

Coconut palms respond to applications of a balanced fertilizer, such as
10-10-30. Organic mulch and fertilizers are good and highly recommended.

Monday, September 1, 2014

Controlling Broadleaf Weeds in Grass

Controlling a grassy weed in a lawn (grass) is difficult since most chemicals cannot distinguish between good and bad grass species. Fortunately, certain herbicides can distinguish between grassy plants and broadleaves. It is the chemical composition of the herbicide and the morphology of the plant that will cause certain herbicides to affect broadleaf plants but not affect grasses. Therefore, controlling broadleaf weeds in a grassy environment is relatively easy. Purchase an herbicide with the active ingredient 2,4-D, MCPP (mecoprop), or dicamba (Banvel). These products are often sold in combination, giving better management and a wider spectrum of the broadleaf weeds controlled.

For light weed infestations, spot treating is more appropriate than treating the entire lawn. Apply just enough of the solution to wet the leaf, do not apply to the point that the herbicide is dripping off the leaf. To insure maximum absorption, stop mowing 2 or 3 days before treatment and allow 3 or 4 days before mowing again. This allows sufficient time for the weeds to absorb the herbicide and transport it to their roots.
Caution: these materials are volitle, espectially 2,4-D. The drift can damage other valued broadleaf plants; tomatoes and hibiscus are particularly sensitive.

Controlling weeds however, should begin long before chemical herbicide applications are considered. Cultural measures ought to be employed from the beginning. These include: 
  • Proper irrigation -  weeds often invade lawns that are either over-watered or under-watered. Perhaps the worst possible irrigation schedule, yet common, is daily watering for 5–10 minutes. Light, frequent irrigation creates a shallow-rooted lawn which is more susceptible to weed invasion, as well as being less tolerant to drought.  In dry areas, where irrigation is employed, water should penetrate to a depth of 6 to 8 inches. The best practice is to allow the soil to partially dry out between irrigation. The top 1 to 2 inches  should be fairly dry before watering again. For more information on irrigating lawns, see UH CTAHR publication, “Watering Lawns”, at

  • Proper fertilization – apply suitable amounts of fertilizer on a regular basis; nitrogen is the key nutrient for turf.
  • Proper mowing heights – each turfgrass species has an appropriate mowing height. Mowing some grasses too short can weaken the lawn and predispose it to weed invasion.  A typical guide is to remove no more than one-third of the leaf blade at each mowing. If too much is removed, it will take more time for the grass to recover, giving weeds a chance to invade.
  • Thatch is a layer of organic matter - stems, stolons, roots - that develops between the turfgrass blades and the soil surface. Regular thatch removal will help keep turfgrass healthy and competitive with weeds.  For Hawaii residents, see the UH CTAHR publication “Removing Thatch from your Lawn” for more information on this procedure.
  • Any activities that lead to soil compaction will contribute significantly to turfgrass stress. This in turn, will make it easier for weeds to invade. These activities may include heavy foot traffic as well as vehicles traveling over the area.

It is very impossible to get 100% weed control in your lawn. Weeds will occur, but the problems can be minimized with a well-managed, vigorously growing lawn. By combining cultural methods with herbicide applications when needed, weeds will  be minimized.