Plant Stand Estimation and Determination of Seed Requirement

Introduction

Estimation of plants per hectare

Solving problems on plants per hectare

Estimation of plant number in a row

Solving problems on plant number in a row

Estimation of intra-row spacing

Solving problems on intra-row spacing

Determination of seed requirement

Estimation of seed quantity

 

Introduction

Establishing a good plant stand in the field is important to ensure good crop yields. Plant stand is expressed either as space between plants or as an optimum plant population per unit area. Both these expressions are interrelated. We can determine the plant population if information on plant spacing is provided. Similarly, if optimum plant population is given, then inter-row and intra-row spacing can be determined.

To ensure adequate plant stand in research plots, a higher seed rate is used at sowing and excess plants are later removed to maintain the required plant population. It is therefore necessary to know the spacing between plants within the row and also the number of plants to be maintained in a given length of row.

                                                                                                                        

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Estimation of plants per hectare

If the spacing of plants within the row and spacing between rows are given, then we can calculate the number of plants in one hectare.

Suppose the row width is 0.75 m and plants are spaced 10 cm apart in the row,

calculate the plant population per ha (or 10,000 sq.m.).

 

                                     10,000 sq m
Plants per hectare = ---------------------------------
                               Plants spacing in sq m

Using the above relationship:

                                 10,000 sq m
Plants per hectare =  ------------------------
                                 0.75 m x 0.10 m
                              = 133,330 plants per ha

 

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Solving problems on plants per hectare

Estimation of plant number in a row

Solving problems on plant number in a row

 

Estimation of intra-row spacing

We can calculate the spacing between the plants within a row, if row width and plant population per ha are known.

Given:      Row width = 0.75 m   Plant population per ha = 150,000

Find:      Spacing between plants within a row.

Step 1: Calculate the row length in a ha based on the row width.

= 10,000 sq m / 0.75 m = 13,333 m

Step 2: Calculate the spacing between plants within this row.

150,000 plants are present in a row of 13,333 m So, spacing between two plants = 13,333 m /150,000

= 0.089 m or 8.9 cm

Therefore, if 150,000 plants are to be established per ha and a spacing of 75 cm is used between the rows, then the plants are to be 8.9 cm apart in the row.

Based on this spacing between the plants, excess plants in a row can be removed.

 

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Solving problems on intra-row spacing

 

Determination of seed requirement

We can calculate the amount of seed required to establish a desired plant stand in the field, considering the quality of the seed. Good seed is a primary prerequisite to establish the required plant stand in the field.

Good seed should:

• be fully mature and capable of germination.
• be free from foreign matter.
• be free from weed and other seeds.
• be free from pathogens and insects.

The seed-lot should be examined before sowing and any deficiency should be adjusted by increasing the seed rate, to obtain the desired plant stand.

 

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Estimation of seed quantity

Estimation of seed quantity per hectare:

Given:  Sorghum seed with 71 % germination, 100-seed mass of 2.8 g, and the required plant population : 250000 plants per ha.

Since the germination percentage is 71, we need to adjust for this deficiency.

Number of seeds needed to get 100 seedlings

    100 x 100
=  ------------ = 141 seeds
        71

Then, the number of seeds required for 250000 plants

     250,000 x 141
= ---------------------- = 352,500
        100

Thus, 352500 seeds are needed to establish 250,000 plants per ha.

The quantity of seeds(seed rate) required per ha.

     352500 x 2.8 g
=  ------------------------ = 9870 g  OR  9.87 kg
           100

Thus, 9.87 kg of seeds are needed per ha.

Estimation of seed quantity per row:

Experimental plot size = 9 m x 4 m    Given:  Sorghum seed with 71 % germination, 100-seed mass of 2.8 g and

Number of rows per plot = 8    Row spacing = 50 cm    Seeds required per ha = 9.87 kg (see previous screen)

Population required: 250000 plants per ha.

Based on the amount of seeds need to be used per ha, we can calculate the required seeds per plot and per row for research plots.

                                             9.87 kg x 1000 g/kg
Seeds needed per sq m =  --------------------------------------- = 0.987 g
                                                10,000  sq m

Plot area = (9m x 4m) = 36 sq m

Seed weight per plot =0.987 x 36 = 35.53 g

Now, calculate the amount of seeds per row.

Single row area = length x width (spacing)

= 9 m x 50 cm = 4.5 sq m

Seeds required per row =0 .987 x 4.5 = 4.441 g

Thus the quantity of seeds required per plot and per row are calculated.

We hope that this lesson has helped you learn to calculate the amount of seed required to establish the desired plant stand in the field.

 

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