Problems with Acidic Soils: Lime Can Work Wonders

Note: pH is the measurement of the soils acidity/alkalinity. The pH scale is from 0 to 14 with 7 as the neutral point; below 7 is acidic, above 7 is alkaline. Here are a few common pH examples:

• Extremely acid:  lemon-2.5; vinegar-3.0; stomach acid-2.0; soda pop-2–4

• Strongly acid:  carrots-5.0; asparagus-5.5; cabbage-5.3

• Slightly acid:  cow's milk-6.5

•  Neutral:  saliva-6.6–7.3; blood-7.3

• Slightly alkaline: eggs-7.6–7.8

• Moderately alkaline: sea water-8.2; sodium bicarbonate-8.4

• Very strongly alkaline: soapy water-12; household bleach-12.5

Concerning the pH of soils, there is a preferred range in which plants will grow best. Most soils in Hawaii, as in other parts of the country, are acidic. Extremely acid soils can have a toxic effect on many plants. One common problem is excessive aluminum and manganese becoming soluble in the soil adversely effecting plants.  Acidic conditions can also change the type of microorganisms living in the soil. This will affect the amounts of nitrogen, sulfur and phosphorus available to the plants since the microorganisms breakdown these nutrients into plant-available forms.

These acidic soils will benefit when lime is applied. As an amendment, lime in its various forms can raise the pH of the soil and eliminate a number of problems.

Ground limestone is almost pure calcium carbonate and comprises the largest percent of lime used in the United States. It is usually the cheapest form of lime. Limestone with significant amounts of magnesium carbonate is called dolomitic limestone (dolomite), containing approximately equal parts of magnesium and calcium carbonate. Dolomite works well especially if the soil has a magnesium deficiency.

Hydrated lime, another form, is one and a half times more effective at raising the soil pH but is also more caustic, and therefore,  hazardous to handle. Protection for the skin and lungs is recommended. Excessive amounts of hydrated lime can cause a pH shift towards a highly alkaline condition. Conversely, when using dolomitic lime, it is difficult to apply too much as long as it is thoroughly mixed into the soil.

When purchasing lime, a fine powdered lime, about 60-100 mesh, is the fastest acting grade available.  However, being a fine powder, it is a potential eye irritant under windy conditions. It will also cake rather easily, and when improperly mixed, it will stratify forming a layer that can burn roots and repel water.

A coarser limestone (similar to salt grains) is also available and is easier to handle, but its disadvantage is that it is slower acting.  In summary, incorporating lime as an amendment in any of its forms can make a big difference in acidic soils.

Passionfruit - Hawaii’s Favorite Flavor

The yellow passionfruit, Passiflora edulis f. flavicarpa, and the purple passionfruit, Passiflora edulis, are grown in most tropical and subtropical parts of the world. The yellow passionfruit is a tropical plant while the purple is considered subtropical, being able to survive some freezing temperatures.

Of the hundreds of species in the genus Passiflora, these two, P. edulis, and P. edulis f. flavicarpa, are solely designated as passionfruit.  In Hawaiian, the fruit is called lilikoi and in Portuguese, maracuja peroba.  When the seeds of purple passionfruit first came to Hawai`i from Australia in 1880, they were planted in East Maui in the District of Lilikoi and that name stayed with the fruit. The seeds of the yellow passionfruit were brought to Hawai`i from Australia in 1923. 

In 1951, there were only a few acres of passionfruit plantings. It was then that the University of Hawai`i chose passionfruit as the most promising crop for development. And by 1958, there were 1,200 acres of primarily yellow passionfruit, and the industry was firmly established.

The lilikoi vine is a shallow rooted perennial, displaying beautiful, fragrant flowers, 2-3 inches wide. The fruit is nearly round approximately 1 ½ - 3 inches wide.  Inside, the fruit is filled with an aromatic mass of juicy pulp and within are as many as 250 small, edible seeds.  These vines, especially the yellow, are fast-growing and will begin to bear in 1 to 3 years. In fact, some vines can flower and fruit within a year after being started from seed. In Hawai`i, passionfruit matures from June through January; the ripe fruit will fall to the ground.

Carpenter bees are efficient pollinators for the yellow passionfruit. Honey bees and the hover fly also help in pollinating but are much less efficient. Wind is ineffective as a pollinator because of the heaviness and stickiness of the pollen.

The yellow lilikoi vine tends to be more vigorous and the fruit generally larger than the purple. While the purple appears to grow better at higher elevations, 400 to 3,000 feet, the yellow fruit is best adapted to lower elevations, from sea level to 1,500 feet. Furthermore, the yellow will yield 3 to 4 times that of the purple, yet the purple fruit is considered to have better flavor and aroma with the pulp being less acid with a higher proportion of juice.

Passionfruit vines are usually grown from seeds.  If the seeds are planted soon after being removed from mature fruit, most will germinate in 2 to 3 weeks. Fortunately, seeds do not require cleaning, drying or storage. They can be planted immediately after being removed from the fruit, even separation from the pulp is not necessary. In fact, allowing the pulp to ferment for a few days may hasten germination. In contrast, seeds that have been cleaned and stored actually have a lower and slower rate of germination. 

Propagation of passionfruit can also be accomplished through air layering and cuttings. Good soil drainage is essential for successful plantings.

Commercially, vines are trained on wire trellises. For backyard production, however, the yellow passionfruit is more productive and less subject to pests and diseases if allowed to climb a tall tree.

In Hawai`i, Oriental and melon fruitflies will deposit eggs in young fruit. This may cause fruit to shrivel and fall from the vine. If older fruit is pierced, the only ill effects will be an external scar. Other pests include aphids, scale, thrips and mites. In spite of all these, passionfruit or lillikoi vines flourish on fences and in trees, in backyards and vacant lots around the Islands.

The juice with its distinct flavor and aromatic bouquet is a key ingredient in making sauce, candy, ice cream, sherbet,  iced tea, or in cocktails.  In the Hawaiian Islands lillikoi is a favorite flavor enjoyed by young and old alike. 

Photos  by Forest and Kim Starr

Heirloom Seeds and Hybrid Seeds

Note:
 In this article, we are not speaking about genetically modified organisms (GMO'S).  A GMO  is a plant, animal, microorganism or other organism whose genetic makeup has been modified using genetic engineering, i.e. gene modification, recombinant DNA methods (also called gene splicing) or transgenic technology.


A hybrid is defined as a plant that results from the cross between two plants of differing genetic characteristics, i.e., two species, subspecies, cultivars, varieties, etc. Some crosses may occur naturally, but most hybridizing is deliberately done by man in order to produce a plant with improved characteristics such as disease resistance, greater vigor and uniformity. Hybrids generally have higher yields and better exterior quality.   

  

Today, hybrid seed is prevalent both in agriculture, as well as home gardening, and is a major contributor to the rise in agricultural output in the last 50 years.  The commercial hybrid market actually began back in the 1920’s, when the first hybrid corn was produced.

The disadvantage of using hybrid seeds is that the resulting seed cannot be used at the end of the season for next year’s crop. The seed taken from a hybrid will either be sterile or produce plants that are not true to the mother plant, i.e., not true to type. Thus it becomes necessary to purchase new hybrid seeds each year. 

On the other hand, heirloom seeds are from open-pollinated varieties. This means that plants grown from these seeds will be identical to their parent.  In addition, their genes have not been subjected to modern breeding techniques and manipulation. Note: All heirloom varieties are open-pollinated but not all open-pollinated varieties are heirlooms.

Heirloom seeds can be saved from year to year and planted for the next crop. Although they may have some built-in hardiness, heirlooms generally do not possess disease resistance, vigor and uniformity that hybrids do.

One of the main advantages attributed to heirlooms is their excellent flavor.  In hybridization programs, plant breeders sacrifice flavor in preference to other attributes such as disease resistance and higher yields.