Tuesday, February 9, 2021

Composting



Composting is a good way to reuse our natural resources, recycle nutrients and add good organic matter back into the soil.  

The popular practice of composting is defined as the process by which organic materials biologically decompose under controlled conditions. Perhaps the most notable point about composting is not to make it more complicated than it is.  By merely throwing a pile of twigs and leaves in the back corner of the garden, you are composting; of course, it may take a year or so to breakdown.  But by following a few simple rules you can speed up the process and produce good compost in about a month or so. The following are key principles:

 a. Proper moisture and air (oxygen) content - Compost works best if the moisture content of the materials is about 50%.  That’s not easy to measure, but it has been estimated to be approximately the moisture content of a wrung-out sponge.  If the material is too dry, decomposition will stop; if too wet, oxygen is excluded, and decomposition will slow and may smell bad. 

b. Proper carbon/nitrogen ratio - For effective composting, the raw materials must have a proper carbon/nitrogen ratio – set at about 30:1.  Since this too cannot be easily measured, mixing equal volumes of green plant material with equal amounts of brown plant material will give this ratio. The greens are fresh moist materials like grass clippings, weeds, manures and kitchen scraps. The browns are dry materials such as twigs, wood chips, straw, saw dust and paper.  If a pile of twigs are thrown to the side, they will eventually decompose. When leaves (greens) are combined with the twigs (browns) in the proper ratios, decomposition will occur more rapidly.    
Mixing grass clippings with twigs or chips is not only good for obtaining the proper ratio but also helps to maintain a good oxygen level.  Grass clippings or shredded papers alone tend to mat and exclude oxygen.  Adding twigs helps to open the pile allowing a better movement of air.   

c. Proper size of material - Soft, succulent plant tissue doesn’t need to be chopped into small pieces because it will decompose rapidly. Woody materials, however, will decompose better if pieces are ½ to 1 ½ inches in size: the smaller the pieces the quicker the decomposition.

d. Proper pile size - The size of the compost pile is important.  The minimal size is 3 cubic feet (3x3x3). Maximum size would be around 5x5 and as long as desired.

e. Proper turning- Turning the pile is not required but will certainly speed up the process if turned every day to every ten days. Turning helps ensure proper air circulation, moisture and heat distribution. 

What should NOT be put into the compost pile? Meat, fat, manure from meat-eating animals as well as human waste. Manure from herbivores such as goats, cows, horses, rabbits and even elephants can be used.  Don't throw diseased plants into the compost pile, because the pile may not reach the temperatures that are required to kill plant diseases and weed seeds. 
Finally, here’s how to know when the composting is ready: the majority of the pile has become dark, loose, crumbly and sweet smelling.  Also, the original materials will not be recognizable with the exception of a few pieces of tough woody material. 

Saturday, January 9, 2021

Seed Germination - Nothing's coming up!





Planting a vegetable garden has a variety of challenges. But how disappointing when the seeds are planted and nothing comes up! Here are primary reasons for poor seed germination.

 1. Planting depth – small seeded vegetables like carrots and onions can easily be planted too deep. If planted too close to the surface, the seed can easily be washed away during heavy rains. Consult the seed packet for proper planting depths. 

2. Temperature – some seed need the soil temperature to warm up before they will adequately germinate, while other cool season vegetables like onions, germinate best in a cool soil. 

 3. Water -  too little and seeds will not germinate or will dry up after germination. With too much water, seeds and seedlings can die from lack of oxygen or be overcome by fungi. Even under normal moisture conditions, different species of fungi and bacteria can cause seeds to rot.  Seeds and seedlings should always be kept moist, but the soil should not remain soaking wet.  

 4. Soil pH - each vegetable seed as well as other plants will have its range in which it will germinate best. 

5. Herbicide residues -  may still be active in the soils causing poor germination.  A high fertilizer content in the soil could also hamper germination. 

6.  Insects will often feed on  seeds and young seedlings.

7. And finally, the seed itself! Poor seed germination can particularly be a problem in humid climates.  Relative humidity influences the moisture content of the seed. The higher the moisture content, the lower the germination rate will be, especially, after one year.


As a general rule, vegetable and flower seeds can be kept for one year without appreciable decrease in germination. Storage, however, may be extended to 10 or more years under proper conditions; seed moisture and temperature are the most important factors. The drier the seeds, the longer they will store.

In humid climates such as Hawaii, storing vegetable seeds in a dry, sealed glass container should keep most seeds viable for a year. For longer storage, place seeds in a moisture-proof container and store in the refrigerator.

Longevity of vegetable seeds will also vary depending on the species.  For example, collards, cucumber, endive, radish and water cress produce some of the hard seeds, rated as lasting 5 years. Next come beets, cabbage, cauliflower, eggplant, kale, mustard, squash, swiss chard, tomato, turnip, watermelon, rated at a 4 year longevity; asparagus, beans,  carrot,  celery,  chinese cabbage, New Zealand spinach, pea, and spinach, at 3 years; leek,  sweet corn, okra and pepper are rated at 2 years; and finally, the last group is rated at a mere 1 year longevity - lettuce, parsley, parsnip and onion.



Photo: Purdue University

Friday, November 6, 2020

Avocado trees - Spots on the leaves?





Originating in Mexico, the persea mite, Oligonychus perseae, was found in California in the early 1990’s and probably came to the Big Island of Hawaii in the early 2000’s. The main host for the mites is avocado trees. Some varieties are more susceptible than others; the Lamb-Haas is considered least susceptible. Many ornamentals and weeds also host the persea mite.  The adult mites have eight legs and an oval body with two dark reddish eye spots near the head end of the body. They lack antennae and body segmentation.


                                                            

Mites feed both on the fruit and leaves, most notably on the underside of leaves. The damage appears as small, circular, yellow to brown spots. Mite colonies often reside against the protruding midrib vein of the underside of the leaves. They produce a dense, silk webbing of protection over them. The webbing resembles a silvery spot on the underside of the leaf, often seen glistening under sunlight.  


Premature leaf drop will begin once the feeding damage to the leaves reaches and exceeds 10% of the surface area. This can lead to sunburned bark and fruit; yields have been reduced up to 20 %.  Trees will recover from the defoliation by producing a new flush. But repeated dropping of the foliage will severely stress the tree.


In the home garden, some mites can be tolerated. Several species of natural enemies often reduce the population of the mites. If numbers get too high, horticultural oils will suppress the mite population. It is important that the spray solution contact the undersides of the leaves, where mites are located. Where feasible, spraying the undersides with a forceful stream of water can also reduce mite populations. By using hydrated lime or diluted white latex paint, a whitewashing on the trunk and major limbs will help protect bark and wood from sunburn after a premature leaf drop.

Photo of Mites: UC IPM Program