Introduction:
While most crop yields are often limited by factors beyond the control
of the farmer, such as the lack of rain or cool temperatures, they
are most often limited by one or more of the factors farmers can control,
such as proper seed, adequate soil nutrient availability, plant population,
and planting date (#1). If these factors are optimized for every crop,
yields would be substantially higher.
The objective in spacing crop plants is to obtain the maximum yield
on a unit area without the sacrifice of quality (#2). The rate of
seeding is governed by the ultimate crop stand desired. Most crops
are selected at lighter rates under dry land than under humid or
irrigated conditions.
Most of the crops we will be using are going to be generally planted
in rows. It has been determined in many experiments that crops planted
in wide rows often resulted in lower yields, even under most dryland
conditions. Similarly, under semiarid conditions the highest yields
on most crops were obtained when single seeds were planted.
Concept #1:
Methods of planting different crops in the area.
Before we can plan the cropping methods to use in the crop production
unit we need the following information:
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Crops that are adapted or could be adapted to the area where
we are going to work.
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What crops are planted during what season.
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Seed availability.
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Water availability.
Activity # 1: With the help of the participants
make a table of the major crops grown in the area. The table should
include varieties of different crops and their respective planting
dates. Questions that the instructor can use are: What crops do
you plant during the rainy season? What crops do you plant after
the rainy season, if any? Why? What crops do you plant where you
have irrigation? Why?
Concept # 2:
Importance of planting date, planting systems, plant population,
and seeding depth of selected crops to be used in the production
unit.
Few management decisions are as important in successful crop production
as those made at planting time. How well you answer questions about
the best planting date, the best population, and the best row width
for your soil and weather conditions will greatly influence the
outcome of your crop.
Planting date:
Crop requirements for temperature, moisture, and light are the major
factors to consider to determine the best planting date (#3). Understanding
these factors will help us decide the month or week of the year when
planting should be done to obtain optimum yields. In tropical areas,
where temperature and light are uniform, humidity will be the main
factor to consider to determine when to plant. In mild areas, temperature,
rainfall, and day length need to be considered when determining the
planting date.
The best planting date for the area, based on the environmental
factors and high production of the region, is reflected in the regional
planting dates. Generally, planting crops out of their planting
date will more likely result in lower yields, no matter how much
fertilizer you use or how well you take care of the crop.
Planting systems
Among the different planting systems, the crops used in the production
unit may require any or all of the following (#4):
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Broadcast:
Spreading seeds throughout the field and then incorporating
them with a harrow. Broadcast planting is not used very often.
However, sometimes small grains (wheat, barley, oats, rice)
are planted using this method. Usually due to the irregular
depth the seeds are incorporated, germination is not very good
and the farmer will need more seed to secure a good crop stand.
-
Rows:
-
Continuous seeds in the row at irregular distance between
seeds. This is a more common method for planting small grains.
Seed depth is more uniform with this type of planting.
-
Seeds spaced at uniform distance. Precision planting, with
uniform distance between or group of plants in a row, is
used for crops like corn, beans, peas, soybeans and garbanzo.
These crops are sensitive to spacing and they require uniform
distances between plants.
-
Seeds planted at same distance from row to row and seed
to seed. This type of planting is used when it is necessary
to cultivate the crop down the row and across.
-
Continuous seeds planted in double row. Sometimes, to make
harvesting easier and to better utilize the land, peas and
soybeans are planted in double row.
-
Furrows:
-
Seeds planted in the furrow at a uniform distance between
them (#5). In semiarid areas or during the dry season, corn
and beans are planted in the furrow to take advantage of
the available moisture.
-
Seeds planted on top of the furrow at a uniform distance
between them. In area with frequent rainfall, corn and beans
are planted on top of the furrow to avoid water logging
the seeds.
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Seeds planted in groups of two to three at a uniform distance
between them.
-
Intercropping:
Two crops interplanted, one row with one crop and another with another
crop (#6).
Farmers need to adopt the planting systems that have been proved
will work in their land and will produce good yields. The following
factors need to be taken into account when planting the production
unit:
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Specific variety or crop requirements.
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The area, soils, and climatic conditions.
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Purpose of the crop.
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Available equipment (#7).
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Manual or mechanized crop management.
Plant Population or Seed Density
Plant population will depend on the soil, climate, and the type
of crop being planted (#8). For example, under extreme conditions,
in poor soils, and in semiarid regions with no irrigation, planting
is best done at low population. Otherwise, you will get thin and
weak plants. Such condition not only produces low yields, but also
is the ideal condition for pests and diseases. Plant population
per hectare depends of the following factors:
-
Soil fertility. In poor soils plant population should be lower
than in soils with high fertility.
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Soil structure. Crops will do better in heavy or light types
of soils.
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Availability of water. In areas where water is a limiting factor
planting should be done at a lower density.
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Tillering capacity of the crop. Small grains and other cereals
are planted at lower densities due to the tillers or spikes
that they develop.
Planting seed depth
Seed depth will vary according to the size of the seed and the available
moisture in the soil. In general, seeds are planted at a depth of
two to four times the size of the seed. In wet or heavy soils seeds
are planted just below the soil surface. On light or dry soils seeds
are generally planted at a deeper depth. The following table gives
approximate planting seed depths (#9).
2 to 4 cm Wheat, barley, oats, sorghum, rice
3 to 5 cm Beans, peas, garbanzo beans, faba beans
4 to 8 cm Corn, soybeans, peanuts
Single vs. multiple seeding practice (#10)
The number of seeds that need to be planted per meter or foot of
row length depends entirely on the plant population and row widths
that have been chosen according to recommendations. The main concern
is deciding whether single or multiple seeding should be used. In
single seed planting, mechanical planters drop seeds out one at
a time along the row. Small farmers who hand plant their crops usually
use multiple seed planting (hill planting), sowing several seeds
per hole and spacing the holes rather far apart. This reduces time
and labor and also may improve seedling emergence under crusty soil
conditions, but it may lower yields somewhat because of inefficient
use of space and increased competition between the plants within
a hill for sunlight, water, and nutrients.
Activity # 3: Calculating the number of
seeds per meter of row for crops in the production unit:
(# seeds per meter of row) / [(% germination) X (% expected emergence)]
= desired population per meter of row
Example: You want to plant a crop with a population of 20 seeds
per meter of row. The percent germination calculated for this specific
seed was determined to be 85. The expected emergence was determined
to be 90 %. Calculate the number of seeds per meter of row to be
planted of this specific crop.
20/ [(.85) X (.90)] = 26 seeds per meter of row
Layout a plan for the production unit with proper row and plant
spacings.
List of figures for lesson 1.4
(Click on the numbered links below to view and print full-sized
figures)
 1. Drawing of an arid soil (hot and dry).
2. Drawing of crop planted showing rows.
3. Drawing of a calendar.
4. Drawing of different planting methods.
5. Drawing of a field with a row crop.
6. Drawing of a field with intercropping.
7. Drawing of a seed bag and planting equipment.
8. Drawing of two fields with different population.
9. Drawing of a different size seed planting
depth.
10. Drawing of a comparison of single and
multiple seed planting field.
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