Corn Production in the Tropics: The Hawaii Experience

76 Pages·2016·3.39 MB·English

by  Brewbaker J.L.

Corn Production

in the Tropics

The Hawaii Experience

James L. Brewbaker
University of Hawaii at Manoa
Corn produCtion in the tropiCs: the hawaii experienCe
Copyright 2003
College of Tropical Agriculture and Human Resources
University of Hawaii at Manoa
Written and revised 1996–2003 by
James L. Brewbaker
Department of Tropical Plant and Soil Sciences
College of Tropical Agriculture and Human Resources
University of Hawaii at Manoa
All rights reserved. No part of this book may be repro- Cover photo
duced or transmitted in any form or by any means, elec- Corn ears from trials in Waimanalo, Hawaii, display
tronic or mechanical, including photocopying, recording, some of corn’s impressive genetic diversity (photo
or by any information storage and retrieval system, courtesy of Sarah Nourse Styan).
without permission in writing from the author.
Key to corn ears shown
Neither the University of Hawaii, the College of Tropical 1 Reventador (Mexican Highland popcorn)

Agriculture and Human Resources, nor the author shall 2 Chocolate (mutant with bronze pericarp)

be liable for any damages resulting from the use of or 3 Coastal tropical flint (W. Indies)

reliance on the information contained in this publication, 4 Argentine popcorn (with red aleurone)

or from any omissions to it. Mention of a trademark, 5 Coroico (Bolivian flint)

company, or proprietary name does not constitute an 6 Floury (mutant floury-2, high lysine)

endorsement, guarantee, or warranty by the publisher 7 Chandelle (Venezuela, white flint)

or its employees and does not imply recommendation to 8 Mishca negrito (Colombia, blue dent)

the exclusion of other suitable products or companies. 9 Canario de Ocho (Brazil, yellow floury)

Pesticide use is governed by state and federal regulations. 10 Pagaladroga (Peru, red floury)

Read the pesticide label to ensure that the intended use is 11 Nal-Tel (Guatemala, Maya Indian corn)

included on it, and follow all label directions. 12 Alazan (Peru, red floury)

13 San Marceno (Guatemala, yellow flint)

Copies of this publication may be purchased from the 14 Chapalote (Anazasi Indian corn, bronze)

CTAHR Publications and Information Office, 3050 15 Teopod (mutant with husk on each seed)

Maile Way, Honolulu, HI 96822, (808) 956-7036, e-mail: 16 Yellow:red in 13:3 ratio (CI/C R/r self)

[email protected], Web: www.ctahr.hawaii.edu. 17 Yellow flint

18 Araguito (Venezuela, popcorn)

ISBN 1-929325-15-0
14
13
15
1
16
Note on measurement

11
Corn biomass and silage yields are expressed in tons/acre.
17
Grain yields are expressed in bushels/acre (bu/A).

10
18
1 acre (A) = 0.4 hectare (ha)

1 bu holds 55 lb of “No. 2 flats” dry corn grain, thus the weight
1
9
of a bushel varies with the type of corn; therefore, 1 bu dry
grain weighs approximately 55 lb
1 ton/ha = 15.9 bu/A

1 ton per acre (t/A) = 000 pounds per acre (lb/A) = 8
35.7 bushels per acre (bu/A) =
.5 metric tons per hectare (MT/ha) 7 3
1 MT = 1000 kg = 00 pounds (lb) = 1.1 ton
100 bu/A = .8 t/A = 6.3 MT/ha 6 5 4

Preface and Acknowledgments

When the project of creating this production manual of Hawaii (UH) varieties and hybrids undergird this
was begun (around 1975), the document owed much to industry. They are grown increasingly throughout the
Sam Aldrich’s excellent but Corn Belt–based Modern world, while Hawaii’s markets often seem hopelessly
Corn Production. Today it owes as much to Web sites naive about the superb quality of this product (given a
(see References), but in general it is patterned on the little tender loving postharvest care).
treatment of the subject by Aldrich. Field corn production for silage or grain in Hawaii
Tropical islands have an annoying way of providing has been limited by lack of suitable land, presence of
a suitable climate to grow any plant without providing tropical plant diseases, and poor market conditions.
the market conditions to make it economically viable. The first of these problems has diminished through
This is certainly true of corn production in Hawaii. the decline of sugarcane production. The second has
Perhaps the most exciting market for our field corn was diminished greatly due to the release of pest- and dis-
for shipment to California during World War I! Since ease-resistant UH hybrids. The third factor, markets,
1970, however, corn has become a significant winter can vary wildly in Hawaii, as animal producers have
seed industry for Hawaii, and Hawaiian supersweets varying interests in locally grown corn grain and silage
have become firmly established as a vegetable crop. for improved production of milk and finished beef, or
Corn is no newcomer to Hawaii. The Royal Hawai- for swine and poultry feeding.
ian Agricultural Society was encouraging research on Problems still abound; for example, Hawaii’s corn
“Indian corn” in the 1850s. They recognized that pest farmers have expenses for land, water, inter-island trans-
resistance was the principal problem in adapting corn portation, and equipment that are an order of magnitude
from the Mainland states to Hawaii. Only in the early above those of the Corn Belt. Tropical weeds, insects,
1900s did corn flourish, but production was restricted to pheasants, feral pigs, and even escaped pet parrots take
Hawaii’s highlands due to a major tropical plant virus their toll. Good corn farmers are hard to find. Even
disease. Hawaii’s generous climate fails by providing too little
Economic production of corn in Hawaii, as in the light and too much wind. I write this manual, however,
rest of the world, rests firmly on the availability of su- with an optimism that Hawaii’s corn production and its
perior adapted varieties, excellent crop land, competent role in international corn improvement have exciting
farmers, and a reliable market. Only in recent years futures.
have these elements begun to come together in Hawaii, The present edition of this book owes much to the
although farmers continue to be plagued by high costs, editorial skills of Dale Evans, Publications and Infor-
infrastructure problems, and a poor business climate. mation Office, UH College of Tropical Agriculture and
Seed corn has become one of Hawaii’s significant Human Resources.
agricultural industries. Hawaii’s seed industry has grown No publication of this magnitude is the product of
since 1966 to involve most of the seed companies and a single person, particularly when it has developed over
many of the corn research institutions in the United more than a quarter-century. I owe great thanks to my
States. It has an enlarging international role in relation students and colleagues for their inputs, criticisms, and
to many crops. suggestions. Fellow authors include
Supersweet vegetable corns have become a bur- Dr. Jay H. Chung (until recently, administrator with
geoning market for Hawaii’s farmers, and University Asian Development Bank, Manila, Philippines)
3
Corn produCtion in the tropiCs: the hawaii experienCe
Dr. Hyeun Gui Moon, corn breeder, Office of Rural Agro-nomy and Soil Science) have figured prominently
Development, Suwon, Korea in my corn research over the years. Among those who
Dr. Soon Kwon Kim, director general, International have helped in preparing and editing this manual are
Agricultural Research Institute, Kyungpook National Dr. Sarah Nourse (Styan), with MS from Wageningen,
University, Taegu, Korea Netherlands
Dr. John Thompson, retired professor of agronomy, Dr. Xiaowu Lu, with MS from Beijing University, Bei-
University of Hawaii (deceased). jing, ROC
Dr. Myoung Hoon Lee, professor, Dongguk University,
Graduate students in CTAHR’s Department of Seoul, Korea
Tropical Plant and Soil Sciences (which combines the Mr. Yoonsup So, graduate student.
former Department of Horticulture and Department of
James L. Brewbaker
Honolulu, Hawaii, 2003
About the Author
James Lynn Brewbaker (“Dr. B.” to his students) has College of Tropical Agriculture and Human Resources
been associated with corn since his birth in 1926, the year of the University of Hawaii.
his father (Harvey E.) completed a PhD in plant breeding He soon initiated a program of regular corn plantings
at the University of Minnesota. Harvey’s mentor, Dr. throughout the year at the Waimanalo Research Station.
Herbert Kendall Hayes, had been a student at Harvard In a widely quoted speech to the American Seed Trade
of Professor Edward M. East, one of the co-discoverers Association in 1974, he reported that his staff harvested
of Gregor Mendel’s definitive research establishing the year-round every Tuesday morning. Using no pesticides,
science of genetics. The names East and Hayes, together a continuing evolution occurred between diseases, pests,
with their students (e.g., Emerson, Mangelsdorf, Jones, and Hawaii’s home-bred corn. Today, Waimanalo-bred
Burnham, Brink, Rinke, Warner, Wortman) are associ- corns effectively can be grown without pesticides, having
ated with every major finding about the genetics of corn high levels of resistance to a host of diseases, pests, and
in the 20th century. Their discoveries and applications of stresses peculiar to the Hawaiian Islands. During these
hybrid vigor in corn alone are worth billions of dollars years, experiments led to the founding of Hawaii’s corn
annually throughout the world. seed industry and of the Hawaii Crop Improvement As-
Harvey Brewbaker served as an assistant professor in sociation (1969). An estimated 1200 trials of corn have
the corn program at St. Paul until 1930, when he moved been planted at Waimanalo through these years. Some
the family to Colorado to assume a position on sugarbeet of Dr. B’s inbreds and varieties have over 70 generations
improvement. Naturally, he grew corn in his backyard of breeding.
in Ft. Collins, where his son got his first experience pol- Dr. B’s students to the MS and PhD degrees number
linating, standing on a box that he carried through the over 50 and are among his proudest accomplishments.
field. They later moved to a farm near Longmont. His publications number over 250 and include four
In 1953, following his PhD under Dr. Sanford S. books, ranging from Agricultural Genetics in 1963 to
Atwood at Cornell and a postdoctoral position with Quantitative Genetics on a Spreadsheet in 1994. His
Professor Arne Muntzing at University of Lund, Sweden, corn inbreds, varieties, conversions, and hybrids are used
the author went to Southeast Asia. There he worked on throughout the tropics. The journal MAYDICA honored
a corn and rice project with Dr. Hayes (then “retired”) him in 1999 with a commemorative issue, “Bringing
and Dr. Dioscoro Umali at the University of the Philip- Maize Genetics to the Mid-Pacific,” v. 44, issue 3, pp.
pines. Two years later he joined the U.S. Atomic Energy 263–384.
Commission in radiation genetics. In 1961, he joined
the faculty of the new Department of Horticulture in the
4
Table of Contents

Chapter 1—Corn and Its Environment
Tillage practices and crop rotation ........................ 48

Corn production around the world .......................... 7
Herbicides; herbicide-resistant corn ..................... 49

Hawaii’s corn production ........................................ 8
Four major classes of preemergence herbicides;

Corn’s environmental requirements ........................ 9
environmental concerns ...................................... 50

Corn’s many uses and markets .............................. 12

Chapter 8—Diseases and Pests

Chapter 2—The Corn Plant
Pesticide-free corn production .............................. 51

Origin and evolution of corn; wild relatives; corn
Diseases ................................................................ 51

and early American civilization; the corn seed .. 13
Maize mosaic virus; other viruses; common rust;

Growth of the corn seedling .................................. 15
southern rust; northern corn leaf blight; southern

The maturing corn plant ........................................ 16
corn leaf blight; yellow leaf blight; bacterial

The developing ear and kernel .............................. 17
diseases; brown spot; rots of seedling, ear, and

The mutants of corn .............................................. 19
kernel; smut

Insects and mites ................................................... 56

Chapter 3—Hybrids and Varieties

Corn earworm, borers, planthoppers, thrips,

Good seed doesn’t cost, it pays ............................. 21

mites, aphids, beetles

Varieties and hybrids ............................................. 22

Miscellaneous pests; pests and diseases Hawaii

Recommended hybrids for Hawaii ....................... 23

doesn’t want........................................................ 58

Major types of field and sweet corn ...................... 24

Pesticides and BT transgenics ............................... 59

Seed production, storage, viability, maturity ........ 25

Adaptability and yield tests ................................... 26
Chapter 9—Harvesting and the Harvested Crop

Grain ..................................................................... 61

Chapter 4—Land Preparation and Planting

Chemical constitution, specialty corns, time of

Seedbed preparation; tilth ..................................... 29

harvest, grain drying

Plowing; secondary tillage .................................... 30

Green-chop and silage .......................................... 62

No-tillage; plant density ........................................ 31

Green-chop, silage hybrids, consideration at

Planters and planting depth ................................... 32

planting, consideration at harvest, a microwave

Chapter 5—Fertilizers
test for silage moisture, silos and silage-making

N, P, and K ............................................................ 35
Vegetable corns ..................................................... 64

Rates of N, P, and K uptake .................................. 37
Baby corn, supersweet corn, time of harvest

Secondary nutrients, micronutrients and lime;

Chapter 10—The Corn Seed Industry

lime and soil pH ................................................. 38

Accelerating genetic progress; Hawaii’s seed

Fertilizer application; organic fertilizers ............... 39

industry ............................................................... 67

Soil and tissue testing ........................................... 40

History of Hawaii’s seed industry ......................... 68

Chapter 6—Water
A unique production regime; Hawaii Crop

Pan evaporation and evapotranspiration ............... 43
Improvement Association ................................... 69

Water-use efficiency; symptoms of moisture stress; .

Appendix 1.

breeding drought tolerance;

References and supplementary reading ................ 70

irrigation water needs ......................................... 44

Forms of irrigation ................................................ 45
Appendix 2. Some favorite recipes for Hawaii’s super-
Salinity and irrigation ........................................... 46
sweet corn ............................................................. 72

Chapter 7—Weed Control
Index ......................................................................... 74

Major weeds in Hawaii’s corn fields;

weed competition and yield loss ........................ 47

5
Corn produCtion in the tropiCs: the hawaii experienCe
6
Chapter 1
Corn and Its Environment

C
orn evolved in the American tropics, where it Corn production around the world
became a staple food of all early civilizations Corn is one of the world’s three major crops, along with
of native Americans. It was named “mais” in rice and wheat. The major corn-producing countries in
Spanish, or “maize,” from which Linnaeus coined its year 2000 were led by the USA and China (Table 1.1).
Latin name, Zea mays. Modern corns never grow wild As intimated by the table, corn is found in every country
but survive only through man’s care. Thus corn’s history in the world and occupies more acreage than any other
is completely interwoven with the histories of the Olmec, crop except wheat. While rice is grown mainly in the
Maya, Teotihuacan, Zapotec, Aztec, Nazca, Iroquois, tropics and wheat is largely a temperate crop, corn is
Inca, and other peoples under whose guidance it evolved grown commercially from Alaska to the equator and
(Brewbaker 1979, Mangelsdorf 1974). from sea level to elevations over 10,000 feet.
In the 500 years since Columbus arrived in the New Production in Asia has increased greatly as use of
World, corn has spread beyond the Americas to become meat in the diets increases. Korea, for example, imports
the world’s most widely distributed crop. It is grown millions of tons of corn as feed and also produces corn on
on about 300,000,000 acres of land, and more than 70 extensive acreage for food (even to make corn noodles)
countries have 200,000 acres or more in corn. About a and feed. World production of corn has increased steadily
quarter of this acreage—and over half the world’s total since 1950, from about 150 million to 550 million tons
production—is in the USA. in industrialized countries, and from about 50 million to
Few crops are found in such diverse forms as corn: sweet over 200 million tons in developing countries. The real
and supersweet corns eaten as vegetables, popcorns, price trend in international markets has been downward,
dent and flint feed corns, corn as an energy crop, floury from about 10 cents/lb in 1950 to 5 cents/lb in 1990.
and high-lysine and waxy (glutinous) and high-amylose Corn production in the USA has been based on
corns. Corn products occur in about one of every five about 75 million production acres. Yields have increased
items in a supermarket, ranging from sodapop to plastics. steadily since the 1960s and greatly exceed all other
The increasingly economical uses of high-fructose corn cereal crops at present. Figure 1.1 shows that this is
sugar and of alcohols, starches, and oils from corn ensure a linear increase, averaging almost 3 percent gain per
that the list of products containing corn will continue year. Scientists attribute over half of this increase to
to expand. plant breeding, or an annual return on investment in corn
The demand for corn increases in proportion to world breeding of about $300 million.
population growth—an awesome 2 percent annually. A large international market is developing for Ameri-
Production has not been able to keep pace with this can corn, including tropical hybrids bred in Hawaii, as
demand, except in a very few countries. The USA is tropical nations achieve demographic transition. The
the world’s major exporter—about a third of its crop. limited public investment in the USA toward improv-
Despite the origin of maize in the tropics, much of the ing tropical agriculture restricts corn self-sufficiency
world’s present corn production is in temperate zones, abroad.
using corn varieties developed for temperate climates Yields of silage corn grown in the USA, for use
and latitudes. These highly productive temperate-zone primarily by dairies, average about 15 tons/acre. Similar
varieties are based on only a fraction (less than 5 percent) yields are obtained in countries like Australia, Korea, and
of corn’s germplasm. Italy, where yields are about double the world average.
7
Corn produCtion in the tropiCs: the hawaii experienCe
The U.S. corn grain yield of approximately 4 tons per States, using high intensity production systems involving
acre (145 bushels per acre) is about ten times that of high plant densities, superb hybrids, and high inputs.
most developing countries, which are largely tropical. Yields since 2000 have exceeded 440 bushels of grain
Essentially all corn grown in the USA is hybrid per acre, equal to more than 12 tons/acre. These values
corn. The yield increase since 1960 shown in Figure 1.1 continue to increase, indicating a significant exploitable
is based almost entirely on single-cross hybrids. These yield gap for farmers and scientists.
succeeded open-pollinated varieties (to 1940) and later
double-cross hybrids (to 1960), types still common in Hawaii’s corn production
the tropics. The development of superior single-cross Corn production worldwide is presented in Table 1.2 in
hybrids for Hawaii can contribute to major increases in terms of the number of people per acre of corn. The United
corn production in the state—if and when the hybrids States has only 3 people per corn acre, as it produces about
are adopted and produced by growers. a quarter of the world production but has less than 4%
Corn-grower contests are held annually in the United of its people, The world has about 20 people per acre of
corn, while Hawaii has almost 300 people per acre. Corn
production in Hawaii thus falls far short of meeting the
Figure 1.1. Corn yields in the USA, 1960–1998.
state’s market demand for any type of corn—whether for
sweet corn, popcorn, silage corn, or grain.
Hawaii cannot grow U.S. Corn Belt corn varieties
e) commercially without high inputs for disease and pest
cr
a control. We must rely instead on hybrids derived from
er germplasm adapted to tropical conditions. There is great
p
els scope for increasing the diversity, yield, quality, and pest
h
s resistance of corn varieties for the tropics and subtrop-
u
d (b ics, as the author’s work at the University of Hawaii has
el demonstrated over the years. This publication focuses on
Yi
the production and uses of corn in the state of Hawaii,
but its information is applicable to many of the world’s
warm regions. Hawaii, at about 20°N latitude, has a
Year subtropical climate and a representative range of the
Figure 1.. Cash value of corn production in Hawaii. Figure 1.3. Acreage of corn production in Hawaii.
US $) acres
n n
o o
milli ucti
e ( od
u Pr
al
V
71 73 75 77 79 81 83 85 87 89 91 93 95 97 99 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99
Year Year
8
Corn and its environment
Table 1.1. World corn production in the major producing Table 1.. Corn production and the human population.
countries.
Annual corn People
Country Production Yield Population production per
(million tons) (tons/acre) acre
Locale in 1995 (acres) of corn
USA 177.3 3.6
China 81.8 1.9
Brazil 1.8 0.8 Hawaii 1,100,000 4000 275.0
Mexico 11.8 0.8
USA 240,000,000 75,000,000 3.2
France 10.9 3.0
Russia 10. 1.
S. Africa 8.8 1.
India 8. 0.7
Yugoslavia 7.7 1.6
Romania 7.3 1.4
in the 1990s, this industry continued to expand. Sweet
Canada 6.4 3.0
corn production has increased since the introduction of
Indonesia 5.9 0.9
Hungary 5.8 .5 Hawaii-bred hybrids such as the Hawaiian supersweet
Italy 5.5 3.4 varieties. Sweet corn has been called “America’s favorite
Argentina 5.5 1.5
vegetable,” but Hawaii’s production still falls far short
Philippines 4.4 0.6
of local demand.
Thailand 3.6 1.1
Spain .9 .9 Field corn grown for grain or silage (“green chop”)
Kenya .4 0.8 has been variously successful since World War II in Ha-
Tanzania .4 0.6 waii. Failures were attributed largely to high production
Nigeria 1.8 0.6
costs, questionable management practices, and a difficult
Zimbabwe 1.6 0.7
local market in the dairy and poultry industries. Since
World total 434 average 1.6
2000 there have been major expansions in production
of silage corn for dairies and of sweet corn.
Corn’s environmental requirements
environmental stresses, plant diseases, insect and weed
pests to which corn is subject throughout the world. Soil
The cash value of Hawaii’s corn crops since 1971 Corn is grown in nearly all types of soil, but major efforts
is summarized in Figure 1.2. Seed corn has risen in may be required to make production feasible. Corn grows
recent years to dominate these numbers; there has been best with good drainage and soil aeration. Croplands
an upward trend in sweet corn but no progress in field of the northeastern USA had to be lined with drainage
corn. Overall, the corn-based industry contributes around systems to improve corn yields over those obtained by
$40 million annually to the state. The high value of the the native Americans. In corn fields with clayey soils,
seed-corn industry inflates the apparent value of Hawaii’s patterns of poor growth due to compaction from heavy
corn crop, but high costs of labor, land, water, supplies, equipment may be visible for years. Liming of soils to
and services reduce net profitability. pH 5.5 and above is required in much of the world.
Crop acreage for seed and sweet corns in Hawaii is For optimum corn yields, the addition of nutrients
summarized in Figure 1.3. Commercial production has is essential on most soils. Growth is best between soil
ranged from 1000 to 3000 acres. These are “crop-acres,” pH 5.5 and 7.3, with pH 6.0–6.5 preferred. In this range,
because Hawaii’s corn lands can produce more than one calcium and magnesium are optimally available, as are
crop per acre per year. The decline in acreage of sugar- the applied phosphates. A good corn soil will have a
cane and pineapple has afforded great opportunity for cation exchange capacity around 20 (milliequivalents per
expanded corn production. 100 g of soil) and a water-holding capacity of 2 inches
The seed corn industry (see Chapter 10) was estab- per foot of soil. In some acidic tropical soils, aluminum
lished in Hawaii in 1966 and grew rapidly, stabilizing in or manganese can become toxic if soil pH is less than
value by the mid-1980s. As new lands became available 5.5. On crushed coral soils and other alkaline soils, pH-
9
Corn produCtion in the tropiCs: the hawaii experienCe
induced deficiencies of minor elements such as iron and (“corn-nuts”) and take up to 250 days to mature. Corn
zinc can reduce yields. production in Hawaii has ranged widely from sea level
to 6000 feet. Corn flourished on the slopes of Haleakala
Temperature crater on Maui in the early part of the century.
Corn is a fast growing crop in the tropics. In Hawaii’s Tropical corn yields generally increase with the el-
lowlands, sweet corn is ripe in 70 days, field corn for evation at which they are planted. The lower temperatures
green chop (silage) is ready in 95 days, and dry grain delay maturity and permit longer development. Plants
is harvested after 110 days of growth. Temperatures in become larger, with more leaves and bigger ears and
these areas range between 70 and 85°F. Below 50°F, corn kernels. While higher yields can be obtained at higher
makes little or no growth. This limitation is recognized elevations, the growing season is longer. Thus any yield
in the “growing degree day” (GDD) formulas for corn, advantage of highland production generally is lost when
which sum the differences between ambient temperature yields are calculated on a per-day basis. Other factors can
and 50°F (see Chapter 3). For example, if average daily also favor lowland production: Hawaii’s highlands are
temperature is 75°F for 10 days, there have been 250 often too wet, with soils that are too acidic or too poor
GDDs. Accurate prediction of the time of flowering is in nutrient status to be suitable for corn production.
important to corn seed producers, and GDD calculations
can allow this. Light
Crop physiologists recognize corn to be a highly Corn and other tropical plants with the C-4 metabolism
efficient type of plant that conserves loss of water by are considered to be highly efficient in harvesting the
respiring not in daylight but only in the dark. Respira- sun’s energy and converting it to growth products. De-
tion is the “living combustion” in which sugars cre- spite this metabolic advantage, light is one of the major
ated in photosynthesis are converted to more complex constraints to maximizing corn yields in the tropics.
products to support plant growth. Respiration’s primary Tropical days are short! In Hawaii they range from 11
waste product, oxygen, needs to be released from the hours 16 minutes to 13 hours 50 minutes (including twi-
plant as carbon dioxide and water. The valves in the light). Rainy periods that involve cloudy, overcast skies
plant’s exhaust system, called stomata, are in the leaf further reduce incident light. This is especially true of
surfaces, and they need to be open during respiration. In windward areas during the winter in Hawaii.
most temperate-zone plants, including wheat and rice, The relationship of corn yield to light in Hawaii is
respiration occurs in the daytime, but in corn and other illustrated in Figure 1.4. Data were taken at Waimanalo,
tropical plants with the “C-4” metabolism, it occurs at
night, when temperatures are cooler. By keeping stomata
closed in the daytime, losses of water are limited, and Figure 1.4. Grain yields (bu/A) at Waimanalo from monthly
C-4 plants are thus “adapted” to warm climates. plantings over a four-year period, with data on solar
radiation (cal/cm /day) for the four months following
Nevertheless, at high temperatures, corn may not
planting.
take up soil moisture rapidly enough to compensate for
plant water loss through the leaves, and wilting can oc-
cur. Plants are most susceptible to drought-induced wilt
during the “grand growth” phase and at the time of pollen
dispersal. Hawaii’s temperatures are relatively constant,
however, and drought stress is rare under irrigation as it
is normally practiced.
Elevation
The speed with which corn reaches maturity is related
directly to the temperature during crop growth, which for
a given region is related to elevation. Corn is grown at el-
evations in excess of 10,000 feet in some locations within
the tropics. Under such cool conditions, varieties such
as ‘Cuzco’ are grown, which develop very large seeds
10