4.1 Counter measure on missing hills

To fill missing hills with other seedlings is important in the trials. Extra seeds could be sown near the plot for transplanting later and fill missing hills. The transplanting for early maturity varieties like upland NERICA should be done 15 days after sowing to allow adequate duration of the vegetative phase, hence seedlings' growth are almost even.

Over-sowing even 10 to 14 days after seeding is late for the early maturity varieties like upland NERICA varieties. Therefore transplanting is recommended to fill the missing hills for the early maturity varieties in variety trial.


Step 1: Plant seeds beside the main plot for transplanting in case of missing hills.

Step 2: Transplanting for missing hills should be done within 15 days after seeding.

Step 3: Use the same number of seedling per hill as in the main plot.

Step 4: Water the transplanted hills.


Note: It is advisable to transplant in a moist soil after raining.


Note: It is advisable to transplant seedlings with soil, and water to the transplanted hills to avoid time lost for seedling recovering after transplanting.

4.2. Growth of rice plant

The growth cycle of the rice plants, taken from a morphological point of view, starts with germination, followed by shoot development comprising leaf emergence and tillering succeeding to elongation of internodes, appearance of the panicles, flowering, grain filling, and maturing of the grains, which is accompanied by a withering stem and leaves, and finally the termination of life. The growing process of the rice plant is separated into the vegetative growth phase and the reproductive growth phase, each of which represented the growth before and after the panicle primordial initiation, respectively, both phases are considered to be qualitatively different from each other (p.119. Vol. 2. Science of the Rice Plant 1995).


Vegetative growth phase:

These two phases are divided more precisely according to the growth conditions of the rice plant. Primarily, the vegetative growth phase is separated into the period in which the young rice plant depends on nutrients in the endosperm only and the succeeding period of the autotrophic rice plant. This phase is characterized by germination of seeds, active tillering, rooting, elongation of plant height, and leaves emergence with certain intervals (p.119. Vol. 2. Science of the Rice Plant 1995).


Reproductive growth phase:

The reproductive growth phase is divided into two stages, before and after heading/ Flowering. The former is a period of panicle development and the later is a period of grain filling and ripening of panicles. The reproductive growth phase starts with the differentiation of panicle primordia. This stage is characterized by panicle development and the elongation of culms, sometimes called the internode elongation stage. Panicle development is further subdivided into some stages extending from differentiation of the primordia to heading and flowering.

Below is a grahp showing an example of the growth of NERICA 4 in case of single plant per hill.

* P.D. = Panicle differentiation stage; P.F. =  panicle formation stage.

4.3. Fertilizer Application

Maximize and homogenize the effectiveness of the mineral fertilizer by noting few points below;

Apply fertilizer in accordance with growth stage to maximize its influence to each yield component such as at the beginning of active tillering stage, panicle formation stage, and meiotic stage.

Apply fertilizer just after rain or in the evening in case it is not rain but you need apply for the trial under the rain-fed upland condition.

Avoid the loss of fertilizer.


4.3.1. Timing of fertilizer application

The timing of mineral fertilizer application is in accordance with growth stage for early maturity varieties under rain-fed condition

The complete fertilizer, N: P: K = 15:15:15 and UREA are widely distributed and used by farmers in West Africa. Appropriate fertilizer application timing and options for early maturity varieties cultivated under rainfed upland condition is still under examination but the data have been gradually collected in the field. In this handbook an option for the topic based on some results of the experiments is temporarily shown below although some points remain to be confirmed in the field.


Basal (N: P: K)

It is advisable to apply the basal fertilizer (N: P: K) to the field around 10 to 14 days after seeding to avoid the loss of fertilizer due to heavy rain until the early seedling stage, around 3rd leaf development stage, specially for sandy soil as the reason we show 2.4. seeding depth. This also fills the role of the top dressing for tillering. Apply fertilizer at latest before 4th leaf finish developing itself.


Note: If young rice plants are covered by weeds, weed prior to fertilizer application. In case weeds are still smaller than young rice plants and/or do not cover the rice, you can incorporate the fertilizer and weeds into the soil at the same time by hoe to make the same effect of intertillage and earthing up.


1st N Top Dressing [Panicle Initiation stage (P.I. stage)]: N fertilizer application is required to increase the number of spikelets per panicle.


Increasing plant tillering is not be enough to maximize yield, especially for panicle weight-type varieties. Application of nitrogen (N) in the reproductive phase is further recommended. The recommended timing of N fertilizer application in the reproductive growth phase is twice, which are at panicle formation stage and meiotic stage. These timing of nitrogen application is closely related with the yield component of rice plant. It is therefore important when the plant is at the panicle formation and meiotic stages for effective utilization of nitrogen.

N top dressing should be timely to maximize production in the field. Early and/or late application of N top dressing may have less effect on yield. In order to attain the objective of maximizing yield it is very important to develop visual indicators for appropriate time of N application. The visual indicators at the panicle differentiation stage (P. D. stage), the panicle formation stage (P. F. stage), and meiotic stage help researchers, agric-extension workers and farmers to apply N fertilizer with appropriate time according to the growth of varieties planted in the trial. Agric-extension workers and farmers can be also benefitted by understanding the visual indicator of these stages to increase their yield.


Visual indicator at panicle differentiation and panicle formation stage:

Panicle differentiation stage: longer leaves appear above the canopy within a plot. The longer leaf is in many cases 3rd leaf before the flag leaf.


Panicle formation stage: when the height of next leaf of the 3rd leaf before flag (2nd leaf before flag leaf) is mostly same height as the 3rd leaf before flag leaf, it begins the panicle formation stage.


Note: When we observe this phenomenon in the field, do not stand closely to a plot, stand few meters away from the plot under observation.

2nd N Top Dressing [Meiotic stage]

Nitrogen fertilizer application is required to increase percentage of ripened kernels in case 1st top dressing (at beginning of the panicle formation stage) is absent, and to tend to maintain the percentage of ripened kernels in case 1st top dressing is implemented, compared to no fertilizer application.

Around 12 days before heading, each mother cell begins to separate from the callose wall and turns irregular in shape. The callose wall is mostly decomposed and a cell free space is formed in the center of the anther locule, which is filled with anther fluid. Each separated mother cell is located on the periphery of the anther locule, and chromosomes synchronously appear in the nucleus; thus the first half of the meiotic stage begins. The separated mother cell enters an isolated state near the inner surface of tapetum. After being divided into two cells by the first meiotic division, tetrads are formed by the second division. Each of the four daughter cells keeps its close position with the tapetum, suggesting a close interrelationship between them (p.312-322. Vol. 1. Science of the Rice plant 1993).

Visual indicator at meiotic stage: This was developed by Dr. Seizo Matsushima (1977). 



Note: The Timing of urea application for top dressing in accordance with time

If you need apply fertilizer not to miss the best timing according to their growing and cannot wait for rain any longer, apply the fertilizer in the evening. Urea can be dissolve by the night dew because it is soluble in water. 

4.4. How do we apply fertilizer in each plot

Before applying the fertilizer we need make boundary around each plot to avoid the loss of the element in fertilizer and to homogenize the effect of the fertilizer in all plots of the variety trial. Be sure the effectiveness of fertilizer in all plots!!

Before applying the fertilizer, divide the fertilizer into two portions. One is two-third of total amount of fertilizer, and the other is one-third to apply homogeneously in a plot.

Firstly, apply homogeneously the two-third of total amount of fertilizer as much as possible in the entire plot, then apply the remaining one-third of the fertilizer much more homogeneously entire plot.


4.4. Fertilizer Calculation

Correct calculation of amount oft fertilizer applied is required for the variety trial.


Example 1 (N: P: K application)

We want to apply a fertilizer at the rate of N: P: K = 30: 30: 30 kg per ha in a plot of 16 m2 using the compound fertilizer of N: P: K = 15: 15: 15.

How much fertilizer is to be applied at the plot?


Step 1: Calculate amount of fertilizer applied per ha.

(1)    If we use compound fertilizer N: P: K = 15: 15: 15.

(2)    We have 100 kg of compound fertilizer (= 2 bags of N: P: K = 15: 15: 15) which has 15 kg of N.

(3)    We can calculate the amount of fertilizer applied per hectare (x) using the formula below.

(100 kg of NPK : 15kg of N  =  x kg of NPK : 30 kg of N)


100 : 15 = x : 30

15x = 3000

 x = 200

Therefore, we need 200kg of NPK compound fertilizer to obtain an application of 30 kg N per ha.


Step 2: Calculate amount of fertilizer applied per plot.

Using the same formula as in step 1 above, we can calculate the amount of fertilizer applied per plot (=y). Noting that plot size is 16m2, and 1 ha = 10,000m2.


10000 : 200 = 16 : y

   10000y = 3200

        y = 0.32 kg (320g)

We need apply 320 g of the NPK=15:15:15 fertilizer per plot (16m2).



Example 2 (Urea application)

We want to apply the UREA [CO (NH2)2] at the plot of 20m2 at the rate of 30 kg of N per ha. How much UREA is to be applied at the plot? C = 12.0, N = 14.0, O = 16.0, H = 1.0


Step 1: Calculate the molecular weight of urea per mol

Step 2: CO (NH2)2 = 12 +16 + (14+1 x 2) x 2 = 12 + 16 + 32 = 60

Step 3: Calculate the proportion of N in the urea

         28 / 60 = 46.666666…… (%)

         We can use the value of 46 (%) for the calculation.


Step 4: Calculate amount of urea applied per ha.

(1)  Given that 100 kg of urea has 46 kg of N (as shown above (step 3), urea has 46% of N).

(2)  If we need to apply 30 kg of N per ha, we can calculate the amount of urea to be applied in 1 ha (x) using the formula below:

(100 kg of urea : 46 kg of N  =  x kg of urea : 30 kg of N)


          100 : 46 = x : 30

                 46x = 3000

                     x = 65.17…..


Therefore, we need 65.2 kg of urea to apply 30kg of N per ha.


Step 5: Calculate amount of urea applied per plot using the above result.

(1)    Given that, the plot = 20 m2 and 1 ha = 10,000m2

(2)    We can use the same formula as above:

10000 : 65.2 = 20 : y

        10000y = 1304

                 y = 0.1304 kg (130g)

Therefore we need to apply 130 g of urea to obtain the 30kgN per plot.


4.5. Weeding

Weed competitions for nutrient always result to significant yield lost. It is therefore necessary to inspect field regularly and weed as and when to minimize competition for nutrients, especially before fertilizer is applied, and to maintain field sanity.  

If a trial field tends to be damaged by rodent, weeding around the trial field is much important.


4.6. Harvesting

Appropriate timing of harvest for upland NERICA varieties are when color of the tip of panicle and primary rachis-branch change from green to brown (more than two-third of the rachis is still green in many case). Approximate moisture contents (%) of filled kernels in three situations are also shown.