2.1. Germination test for variety trial

Seeding is the process of planting seeds into the soil for crop production. Germination test is a prerequisite before seeding to determine seeds viability, and to secure the enough number of emergence seedling by adjustment of seeds sown par hill. Germination test can be done by using a petridish with tissue paper.

Step 1: Take randomly seed from seed lot

Step 2: Count 50 to 100 seeds 3 times

Step 3: Prepare the petridsh or plate, and tissue paper or filter paper

Step 4: Spread the seeds on the paper of the petridish and saturate with water

Step 5: Cover the petridish

Step 6: After 5 days count the number of seeds that germinated

Step 7: Calculate the percentage seed germination

Step 8: Adjust your seed rate per hill according to percentage of germination rate if necessary. 

 

2.2. Seeding method: Dibbling

Dibbling is the seeding method usually used for variety trials. This is the process of planting seeds in pockets at a given spacing, usually 20cm x 20cm between plants and between rows in West Africa. Therefore, the recommended seed rate is around 35 kg/ ha as shown below (The calculation of seed rate depends largely on the weight of the seeds of the variety. Different varieties have different weight of kernels. It is usually shown as the 1000 kernels’ weight).

Around 10 to 14 days after seeding, which is around 3rd leaf age, the number of seedlings par hill can be adjusted to meet the objectives of trial.

 

Note: If we want to know a tillering ability of varieties (finally it is shown the number of panicles at harvesting), we need establish single plant per hill, but in case panicle weight type-early maturity varieties like upland NERICA varieties are included in your trial, their yield may not reach to the maximum in a trial condition because the number of panicles per hill and spikelets per unit area may be less than maximum.

 

Dibbling method

Broadcasting method

Drilling method

2.3. Seeding rates

We can see many seedlings per hill in the field. Five-seeds per hill is in many case the enough number of seeding rates for variety trial with objective of comparing yield of varieties as shown in the table below (In case the germination rate is more than 80%).

Example photos of seeding rate in the field

 

Seeding rate calculation:

Example: For dibbling seeding method

Question: How many grams do we need prepare per plot (5 x 5m) in case plant spacing and row intervals are 20 x 20 cm. We sow 5 seeds per hill. 1000grains weight use 28g.

 

Step 1: There are 25 hills in 1 m2 as shown below.

Step 2: 125 seeds are needed per plot (5 seeds/ hill x 25 hills/ m2 = 125 seeds/ m2) [1,250,000 seeds/ ha]

Step 3: 25m2/ plot x 125 seeds/ m2 = 3125 seeds/ plot    

Step 4: 3125 seeds x 28 g/ 1000 grains = 87.5 g/ plot [1,250,000 seeds x 28g/ 1000 = 35,000g/ha= 35kg/ha]

Step 5: 100g/ plot will be weighed for each plot.

Step 6: Consider the total number of plots per variety (the number of treatments and replicates). 

Note: This (the number of hills per 1m2) is also used for harvesting to collect yield data.

 

2.4. Seeding depth

Germination and emergence at field level can be influenced by the types of soils and planting depth. Planting at a depth of around 3 cm is the optimum sowing depth in a sandy soil. Where as around 2 cm is the ideal depth for clayey soil.

Planting at a depth of more than 5 cm results in low and/or delayed seedling emergence and decrease the number of tillers/ hill. 　

Shallow planting (less than 1.5 cm) in sandy soil under rain-fed upland condition may cause 1) low seedling emergence rate resulted from low moisture content of soil surface due to scarce rainfall after sowing and/or 2) high missing hill rate resulted from washed-away seeds due to heavy rainfall.     

Photos: Situations of the field after heavy rain