Research for Agricultural Sciences: " OPTIMAL HARVESTING METHODS TO REDUCE GRAIN LOSSES " pot

SECTION 1




OPTIMAL HARVESTING METHODS TO REDUCE GRAIN LOSSES
(RAINY 2006 AND DRY SEASONS 2007)

5

Optimal harvesting methods to reduce grain losses

Compilation of results from two consecutive seasons (2006-2007)


In order to determine the actual post harvest losses mainly due to rice cracking, the data was
collected systematically based on the farmers practice and also by experimentations during two
seasons (rainy 2006, dry 2007). The wet season 2007 experiments are being pursued currently.
The main factors which were considered in this study during the collection of data were:

• Harvesting time- before and after grain maturity
• Harvesting methods- manual, reaper, combined harvester
• Drying methods and cost of drying- sun drying and mechanical drying

The behaviour of the rice grain to cracking will depend on the variety and season. Considering
these factors the data were collected for 6 different varieties in 4 different locations of Mekong
River Delta (MRD). The type of the varieties chosen in the repeated season was not under our
control because of the farmers’ practice to change the variety from one to another season.

1. Effect of harvesting time on the rice cracking and head rice yield

Incorrect harvesting time is one of the major factors that cause the losses due to cracking.
Cracking can develop in the field as a result of changes in grain moisture or moisture cycles
after the rice matures due to hot sunny days followed by humid nights. The cracking behaviour
of the rice in the field is expected to depend on the season due to the different patterns of
temperature fluctuation during day and night, degree and strength of sunshine and frequency of
rain. During the rainy season, the rice grain can develop cracks during the late maturity stage
due to rewetting. At the same time, during dry season it is likely that the grains over-dry if not
harvested at the maturity. The objective of this experiment was to determine the effect of
harvesting time on kernel cracking of some rice varieties in two consecutive seasons in the
MRD.

Harvesting time field experiments were conducted in three locations on four most cultivated
rice varieties in those areas (Table 1).

Table 1: Data collection to determine the losses due to current harvesting practices
(harvesting time and methods)

6

Season
Locations Rice variety Harvesting
period
Rainy Tan Thoi 1 cooperative,
Can Tho province
OM 2718,
OM1490
30

May-13 June
2006
Rainy Tan Phat A cooperative,
Kien Giang province
An Giang 24
(AG24)
22-30 July 2006
Rainy Seed centre, An Giang
province
Jasmine June/July 2006
Dry Tan Thoi 1 cooperative,
Can Tho province

OM 2718,
OM1490
6-19

Feb 2007
Dry Tan Phat A cooperative,
Kien Giang province
OM2517,
OM4498
6-19

Feb 2007

According to local survey results, the one or two most cultivated rice varieties OM2718 and
OM1490, OM2517 and OM4498, An Giang 24 and Jasmine were chosen in Can Tho, Kien
Giang and An Giang provinces, respectively. In Tan Thoi 1 cooperative we were able to
experiment with the same variety in both rainy and dry seasons, however due to the change in
the cropping pattern of the farmers the same was not possible in Tan Phat A cooperative.
Therefore, in this cooperative experiment varieties are different in two different seasons.

Using a randomised block design, the rice was harvested 6 days prior and 6 days post-maturity
stages in 2 days intervals (except 1 day interval for An Giang 24 and Jasmine varieties). The
percentage of rice grains with cracks and head rice recovery in a laboratory milling system
were measured for both brown (in original paddy) and white rices.

The full details of the experiments undertaken in two cooperatives (for dry season) including
the experimental design are attached with this report (as appendices 1 and 2).

1.1 Harvesting time and rice cracking
Some selected data on the amount of cracked grains as influenced by the early or late

harvesting from the day of maturity are presented in Figures 1 and 2. The maturity day is taken
as an estimate from farmers experience and available data from the extension office. This value
was 90-91 days for OM1490, OM2718, OM2517, OM4498 and An Giang 24 and 98 days for
Jasmine rice varieties. The head rice recovery was analysed for both brown (after dehulling)
and white (after whitening) rices.

1.1.1 Cracking in brown rice and head rice recovery
Experiments conducted on six common rice varieties in three different locations indicated that
the rice cracking is obviously influenced by both the variety and time of harvesting. The
similar trend was observed in both seasons. Harvesting the rice a few days prior to maturity
will not have much impact on rice cracking, but delayed harvesting will result in significant
rice cracking (up to 60% of total brown rice) depending on the variety. It was interesting to see
large amount of cracked grains in OM2571 (dry season) due to late harvesting. Interestingly,
early harvesting has shown lesser proportion of grain cracks and higher head rice recoveries.
This indicates how important it is to harvest the paddy in time. Any over-drying in the field (or

7
in the panicle) can result in increased number of cracked grains and reduced head rice
recovery.

Our results indicate that there is a varietal difference on rice cracking. It should be noted that
the maturity or optimum harvesting time was an estimate which was almost the same day for
all varieties used in this investigation. If varieties were harvested about the same time, then we
could conclude that 1. Varieties differ considerably in the cracking (hence intervention
opportunity of growing low cracking varieties such as AG24 for farmers and developing such
varieties for rice breeders), 2. Harvesting at optimum harvest time had rather small cracking
problem but delay of 6 days can cause major problem (and hence intervention opportunity
here) 3. Varieties differ in their response to time of harvesting hence time of harvesting is more
critical for some varieties than others (such as OM2517 was the most critical variety), and
hence opportunity for intervention (general recommendation would be to ensure quick

harvesting for particular varieties).

1.1.2 Cracking in white rice
The cracking in the whole white rice kernels were also measured for the same rice variety
samples which were used to determine the brown rice cracking. It is important to know the
level of cracking in the white rice because this will also be important when rice breakage
occurs during post-milling conditions. There is a possibility of split of the grains with severe
cracks during storage, particularly if there is moisture and temperature variations or stresses.
This is the area which will need more investigation (although this does not fall under the scope
of this current project).

The cracked grains were more in the case of white rice than those in brown rice samples. This
is because the proportion of cracked grains is calculated based on the whole white rice kernels,
excluding the broken rice. The weak and fissured brown rice would normally break during the
whitening process. The cracking in the white rice kernels can be developed due to the shear
during the whitening process and some types of the cracks may still be carried over from the
brown rice. Some of the brown rice kernels with minor fissures or cracks may not break during
the whitening process. The varietal difference on the cracking and head rice yield is obvious in
Figure 2.

As a general trend the white grain samples from late harvested crops had more cracked gains
than those harvested earlier than maturity (Table 3). This obviously originates from the higher
amount of cracked grains in late harvested paddies (Table 2). No obvious difference was
observed on the cracked white grains of the same variety between rainy and dry seasons under
the experimental conditions used in this work. The degree of cracking was at the similar range.

8
0.80
3.20
9.60
4.80
10.80
15.20
23.60
0
4
8
12
16
20
24
-6 -4 -2 0 +2 +4 +6
Harvesting time (days from maturity)
Grain cracks (%)
0.40 0.40
1.20
2.80
10.80
4.00

5.20
0
2
4
6
8
10
12
-6 -4 -2 0 +2 +4 +6
Harvesting time (days from maturity)
Grain cracks (%)

Variety: OM 1490 (Rainy) Variety: OM 2718 (Rainy)


Variety: OM 1490 (Dry) Variety: OM 2718 (Dry)
0.13
0.67
1.6
0.4
0.53
1.34 1.33
1.73
5.47
0
2
4
6
8
10

-4 -3 -2 -1 0 +1 +2 +3 +4
Harvesting time (days from maturity)
Grain cracks (%)
4
3.92
5.18
8.66
6
5.14
7.6
0
2
4
6
8
10
-3 -2 -1 0 +1 +2 +3
Harvesting time (days from maturity)
Grain cracks (%)

Variety: An Giang 24 (Rainy) Variety: Jasmine (Rainy)


Variety: OM2517 (Dry) Variety: OM4498 (Dry)

Figure 1: Proportion of cracked brown rice grains as influenced by harvesting time, 4-6 days
earlier (-6 days) and 4-6 days later (+ 6 days) than the predicted day of maturity.
3.73
1.07
1.47 1.47

1.07
2.93
9.33
0.00
2.00
4
6
8
Grain cracks (%)
.00
.00
.00
10.00
-6 -4 -2
0
+2 +4 +6
Harvesting time (days from maturity)
1.47
2.00
3.60
5.73
16.00
33.60
60.53
0.00
10.00
20.00
30.00
40.00
50.00

60.00
70.00
-6 -4 -2
0
+2 +4 +6
Harvesting time
(days from maturity)
Grain cracks (%)
2.40
0.67
6.27
2.00
3.20

7.20
8.53
0.00
1.00
2.00
3.00
4.00
5.
6.
7.
8.
9.
Grain cracks (%)
00
00
00

00
00
-6 -4 -2
0
+2 +4 +6
Harvesting time (days from maturity)

25.00
22.40
20.00
14.40
15.00
10.00
5.60
5.00
2.80
2.27
1.87
0.53
0.00
0
-6 -4 -2 +2 +4 +6
Harvesting time (days from maturity)
Grain cracks (%)

9
1.60
4.40 4.40 4.40
5.20
4.80

11.60
0
2
4
6
8
10
12
-6 -4 -2 0 +2 +4 +6
Harves ting time (days from maturity)
Grain cracks (%)
0.40
1.60
2.80
2.40
3.20
4.40
6.00
0
2
4
6
8
10
12
-6 -4 -2 0 +2 +4 +6
Harves ting time (days from maturity)
Grain cracks (%)

Variety: OM 1490 (Rainy) Variety: OM 2718 (Rainy)

Variety: OM 1490 (Dry) Variety: OM 2718 (Dry)

0.27
0.67
1.47
0.4
0.53
1.07
1.27
1.73
4.13
0
2
4
6
8
10
-4 -3 -2 -1 0 +1 +2 +3 +4
Harvesting time (days from maturity)
Grain cracks (%)
7.4
8
7.8
11.8
8.4
9.4
12.2
0

2
4
6
8
10
12
14
-3 -2 -1 0 +1 +2 +3
Harvesting time (days from maturity)
Grain cracks (%)

Variety: An Giang 24 (AG 24) (Rainy) Variety: Jasmine (Rainy)


Variety: OM2517 (Dry) Variety: OM4498 (Dry)
Figure 2: Proportion of cracked white rice grains as influenced by harvesting time, 4-6 days
earlier (-6 days) and 4-6 days later (+ 6 days) than the predicted day of maturity.
20.40
5.33
7.00
3.87
6.40
8.07
7.53
0.00
5.00
10.00
15.00
20.00
Grain cracks (%)

25.00
-6 -4 -2
0
+2 +4 +6
Harvesting time (days
from maturity)
1.20
35.33
5.60
5.40
8.00
9.33
17.20
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
-6 -4 -2
0
+2 +4 +6
Harvesting time (days from maturity)
Grain cracks (%)
0.33
1.33
3.87

2.07

6.67
10.13
13.47
0.00

2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
-6 -4 -2
0
+2 +4 +6
Harvesting time (days from maturity)

Grain cracks (%)
6.60
3.
4.
5.
6.
Grain cracks (%)
7.00
00
00

00
00
1.80
1.83
2.00
0.67
0.53
1.00
0.33
0.13
0.00
0
-6 -4 -2 +2 +4 +6
Harvesting time (days from maturity)


10
1.2 Harvesting time and head rice recovery
The head rice recoveries as a function of harvesting time for six varieties of rice are presented
in Figure 3. The results indicated that the head rice recovery follows the same opposite trend to
rice grain cracking. This obviously means that the presence of cracks in the original paddy
influenced the head rice recovery. The head rice recovery was less at late harvesting period. A
delay of 4-6 days reduced the head rice recovery by 7-50%.

The overall results as influenced by harvesting time are presented in Table 2. It should be noted
that the head rice recovery was determined by a laboratory milling system. Thus, the head rice
recovery will also be a function of milling efficiency. Therefore, the head rice recovery data
presented in Table 2 is in relative term. In this case, the recovery on the harvesting at maturity
(0 day) was considered as 100%. In addition, due to the limited number of experiments
undertaken (as feasible), the values are presented in the range. The varietal factor has been

incorporated within this range.

Table 2: Seasonal trend of effect of harvesting time before and after maturity (4-6 days prior
and 4-6 days later than the expected day of maturity) on the proportion of cracked grains (prior
to milling) and head rice recovery. Head rice recovery is relative to the recovery on maturity
day.
Proportion of cracked grain % Head rice recovery relative %
Season Rice variety
Before maturity After maturity Before maturity After maturity
OM1490 0.8-9.6 10.8-23.6 106-109 72-88 Rainy
OM2718 0.4-1.2 2.8-10.8 104-117 84-93
OM1490 1.9-2.3 5.6-22.4 98-100 92-98 Dry
OM2718 2.4-6.3 3.2-8.5 93-99 83-95
OM2517 1.5-3.6 16-60.5 80-114 51-94 Dry
OM4498 1.5-3.7 1.1-9.3 75-93 90-98
An Giang (24) 0.5-1.6 1.3-5.1 93-97 83-108 Rainy
Jasmine 4-4.5 6-7.7 75-99 87-99

Table 3: Effect of harvesting time before and after maturity (4-6 days prior and 4-6 days later
than the expected day of maturity) on the proportion of cracked grains in the white rice kernels.
Note that the cracked grains are the whole kernels which survived milling. These cracked
grains are susceptible to breakage during storage even after milling.
Proportion of cracked grain % Season Rice variety
Before maturity After maturity
OM1490 5.2-6.1 7.2-11.6 Rainy
OM2718 0.4-2.8 3.2-6.0
OM1490 0.3-3.9 6.7-13.5 Dry
OM2718 0.1-0.3 0.5-6.6
OM2517 1.2-5.6 8-17.2 Dry
OM4498 5.3-20.4 6.4-7.5

11
An Giang (24) 0.3-1.5 0.5-4.2 Rainy
Jasmine 0.4-2.8 3.2-6.0

45.41
51.47
43.54
43.91
38.76
36.83
40.72
0
5
10
15
20
25
30
35
40
45
50
55
-6 -4 -2 0 +2 +4 +6
Harvesting time (days from maturity)
Head Rice Recovery (%
)
51.06
52.3

50.73
47.99
42.23
36.51
34.53
0
5
10
15
20
25
30
35
40
45
50
55
-6 -4 -2 0 +2 +4 +6
Harvesting time (days from maturity)
Head Rice Recovery (%
)

Variety: OM 2718 (Rainy) Variety: OM1490 (Rainy)

Variety: OM 2718 (Dry) Variety: OM1490 (Dry)
42.35
41.75
40.76
42.51
43.5

46.33
46.99
42.72
35.9
0
5
10
15
20
25
30
35
40
45
50
55
-4 -3 -2 -1 0 +1 +2 +3 +4
Harves ting time (days from maturity)
Head Rice Recovery (%
)
41.59
54.65
51.82
55.36
54.59
48.15
49.46
0
5
10

15
20
25
30
35
40
45
50
55
60
-3 -2 -1 0 +1 +2 +3
Harvesting time (days from maturity)
Head Rice Recovery (%
)

Variety: An Giang (24) (Rainy) Variety: Jasmine (Rainy)

Variety: OM2517 (Dry) Variety: OM4498 (Dry)

43.80
54.35
54.02

58.33
56.95
53.78
52.55
0.00
10.00
20.00

30.00
40.00
50.00
60.00
70.00
-6 -4 -2
0

+2 +4 +6
Harvesting time (days from maturity)
Head Rice Recovery %
64.58
41.09
45.19
56.68
53.18
43.74
28.63
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
-6 -4 -2
0+2 +4 +6
Harvesting time (days from maturity)
Head Rice Recovery %

67.63
67.01
66.40
67.48
66.22
63.81
62.41
59.00
60.00
61.00
62.00
63.00
64.00
65.00
66.00
67.00
68.00
69.00
-6 -4
-2 0+2 +4 +6
Harvesting time (days from maturity)
Head Rice Recovery ((%)
80
67.90
66.93
66.21
1
2
3
4

5
6
7
Head Rice Recovery ( %)
64.57
0
63.13
60.25
56.35
0
0
0
0
0
0
0
-6 -4 -2 0+2
+4 +6
Harvesting time (days from maturity)

12
Figure 3. Influence of harvesting time on the head rice recovery during milling


Conclusion and project intervention method:
The following conclusion can be drawn from the above information:
1. The harvesting time is one of the important factors to control the rice cracking and
eventual head rice recovery. The same effect persisted in rainy or dry season.
2. Varieties differ in their grain cracking and those with small cracking such as AG24 is
recommended (after confirming this results in the next season). When head rice

recovery is also considered, OM1490 is better.
3. With the two varieties investigated in two seasons (wet and dry), the seasonal effect
was not found significant.
4. There is a clear trend that a few days early harvesting (before maturity) is better than
the late harvesting. The intervention opportunity of early harvesting to reduce grain
cracking and increase head rice recovery should be conveyed to the farmers and
extension agency. This extent of this harvesting time effect is also dependent on the
variety.
5. The information gathered will be very useful for the farmers and will be made available
through training. This will highlight the importance of rapid harvesting of the crop.
Farmers are encouraged to make their crop management in such ways that they can
harvest earlier (eg, organize labour for harvesting etc)
6. This is expected to impact to the farmers decision to determine the harvesting time. In
some rice varieties this is expected to reduce the losses substantially, since one of the
varieties tested in this investigation had a proportion of cracked rice as high as 24%.


2. Effect of harvesting methods on the rice cracking , head rice yield and losses

The data collection in the harvesting method has been done in both seasons (rainy and dry).
However, there is some delay on the data analysis for the dry season. Therefore, this result is
only for rainy season. The dry season data will be submitted in the next report once it is
submitted by the harvesting method sub-component collaborator. Note that the following
content is the repeat from the MS4 (baseline data) report.

2.1 Effect of harvesting methods on the rice cracking and head rice yield
Harvesting method used can influence the extent of rice cracking in the field. The harvesting
can be done by hand or machine. As a current practice, harvesting by hand is widely used. In
relation to harvesting method, the cracking of rice is related more to the time duration
necessary to harvest than the methods itself. A fast harvesting during wet season and

harvesting at correct time during dry season is necessary to avoid rewetting or over-drying of
the grain while in the panicle. Unfortunately, due to the lack of the labours during the
harvesting period farmers are not always able to harvest the crop in time which results in
losses.

This work gathered the actual data to determine the effect of harvesting methods on kernel
cracking of some rice varieties in Summer-Spring (rainy) season (June/July) in Can Tho and
Long An provinces. The following harvesting methods were used:

1.
Hand (+ mechanical threshing)
2. Reaper (+mechanical threshing)

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3. Combined harvester (harvesting and threshing combined)

The data were collected from our own experiments as well as from selected farmers field after
their traditional harvests.

Comparison of harvesting methods by experimentation on the head rice recovery was
undertaken in cooperatives in Can Tho and Long An provinces (Table 4). As additional
information, cracking behaviour of the grain due to threshing was also investigated in those
two cooperatives. In each cooperative, the experiments were undertaken in two fields, where
the popular rice variety was grown. The following results were obtained (Table 4) for each
harvesting method applied.


Table 4: Effect of harvesting methods on the head rice yield
Location Harvesting method Notation
Average Head

rice recovery
(%)
Hand and heaped immediately HH 41, 50
Hand and dried in the sun (one
day)
HD 37, 47
Reaper and heaped
immediately
RH 49*
TanThoi
co-operative,
CanTho
(OM 2718, OM1459)
Reaper and dried in the sun
(one day)
RD 52*
Hand and heaped immediately HH 45, 60
Hand and dried on the sun
(one day)
HD 43, 62
GoGon
co-operative, LongAn
(Bu Tin, VN 95-20)
Combined harvester CH 36**,60
*Only one replication due to rain
**Low value due to rain during harvesting

There was a large variation in cracking losses. It might be due to varietal difference and other
uncontrollable factors. It was raining a lot during the experimental period. To achieve an
accurate result, a large number of experiments should be undertaken to reduce the variability in

field condition. This was not feasible due to lack of time and restriction on the resource.
Therefore, this result should be taken as indicative only. The experiments will be repeated in
the dry season (Feb/March). The results have indicated that the head rice yield by reaper is
better or as good as harvested by hand. The main advantage of using the mechanical harvesting
is to shorten the harvesting time in order to avoid the effect of rain or weather change
difference on the head rice yield. We have previously shown that the late harvesting than at
maturity will make the grain more sensitive to cracking. Therefore, any delay or longer
harvesting time can cause more losses, as is the case when the harvesting by hand is practiced.

2.2 Effect of harvesting methods on the threshing losses
The above harvesting methods also affected the losses of grain during subsequent threshing
step. The threshing losses are the fractions of paddy kernels mixed with the impurities removed
by the thresher. These losses are shown in Table 5.


14


Table 5: Effect of harvesting methods on the threshing losses
Location Harvesting method Notation
Losses (%)
Hand and heaped immediately HH 1.4
Hand and dried in the sun (one
day)
HD 1.2
Reaper and heaped immediately RH 1.1
TanThoi
co-operative,
CanTho
(OM 2718, OM1459)

Reaper and dried in the sun (one
day)
RD 0.8
Average 1.1

In general, leaving the rice one day in the sun after cutting prior to threshing (treatments HD
and RD) reduced threshing losses by 0.2%. This reduction can be explained by lower moisture
content of rice after sun drying. The average threshing losses by reaper and hand were 1.0%
and 1.3%, respectively. The overall threshing loss was 1.1%.

Conclusion and project intervention methods:
• The above information indicates that a quick harvesting by reaper method is beneficial
to improve the head rice recovery, but this needs confirmation.
• Since, a rapid harvesting is not possible for small farmers due to their limited financial
capacity; operation of harvesters through farmers cooperative is the best alternative.
This project implements this concept by providing mechanical harvesters to two
cooperatives.
• The cooperatives equipped with harvesters will be used for the demonstration purpose.
Data will be presented to the farmers through training. The farmers will be trained
through extension workers. It is expected that the dissemination of the information to
the local farmers within the catchments area of the cooperative will be spontaneous due
to the engagement of the cooperatives in the activity.
• Head rice recovery varied greatly within a system (eg 45-60% in hand and heaped
immediately in GoGon Cooperative), and identification of the source of the variation
would help increase the head rice recovery.


3. Other harvesting factors contributing to the losses

There are other factors which can contribute to the post-harvest losses. These possible factors

are:
1. Threshing method- hand or machine
2. Shattering of grain due to harvesting method applied


3.1 Effect of threshing method on grain cracking and head rice recovery

The threshing method applied can cause the cracking in the rice kernels and eventually reduce
the head rice recovery. The data were collected in two provinces at the same time when
experiments were conducted as described in the previous section 1. The results are presented
in Table 6. These results indicated that the grain cracking is not significantly affected by the

15
method of threshing. However, some reduction of head rice recovery was observed in the case
of rice threshed by machine.

Table 6: Effect of threshing method on rice cracking and head rice recovery

Grain cracking (%)
Brown rice White rice
Head rice recovery
(%)
Rice
varieties
Hand Machine Hand Machine Hand Machine
OM2718/
OM 1490
4.1 3.9 3.0 1.8 49.9 46.7
An Giang 24
0.9 2.4 1.5 0.7 45.6 44.0

3.2 Losses due to grain shattering during harvest

Although this type of losses is not related to rice cracking, it can be important if a mechanised
method is used to minimise the rice cracking. The losses due to shattering during harvest were
analysed by two methods:

a. Collection of shattered grains in the selected farmers’ field in two provinces (Tan Phat
and Tan Thoi)- harvested by hand: A total of eleven farmers were selected.
Experiments were implemented after farmers harvested and threshed the crop. The
results are presented in Table 7. The losses due to shattering in the rice field was 2.9 %
in average, but was as high as 5%. This loss for Kien Giang was 2.5 ± 1.9 %, while for
Can Tho it was 3.3 ± 1.2%. These values are comparable or higher than those obtained
by PRA method for Summer-Autumn crop (2.4% for Kien Giang and 2.3% for Can
Tho, as reported by DANIDA project, 2003). There is also a clear trend that the
shattered grain is increased when the grain moisture is lower, suggesting that late
harvesting also causes more shattering of grain.

b. Collection of shattered grain from farmers field- harvested by hand and mechanical
methods: These experiments were conducted in two provinces, Cantho and Long An.
The data were collected during the experimentation involving the effect of harvesting
method as described in the previous section. The results are presented in Table 8. Our
experimental results show that cutting by reaper gave lower shattering losses than
cutting by hand (approximately one third). The results also show that cutting by
combined harvester gave lower shattering loss than cutting by hand.

16


Table 7: Losses due to shattering in the field during hand harvesting (Tan Phat and Tan Thoi
cooperatives) by farmers
Farmers’
number
Rice
varieties
Initial
moisture
content
(pre-
harvest)
Grain
moisture
during
threshing
Shattered
grains (g)
per 25m
2

Productivi
ty
(kg/1000
m
2
)
% Loss
1 OM 2517 23.4 28.9 445 550 2.6
2 20.4 26.5 320 450 2.2
3 24.5 29.3 182 380 1.6
4 23.8 27.9 290 440 2.2
5 22.9 28.4 220 480 1.5
6
AG 24

18.9 19.4 538 400 5.2
7 22.5 24.8 285 350 3.6
8
OM 1490
20.3 23.7 298 300 4.6
9 22.8 19.4 262 380 2.3
10 27.6 22.1 305 400 2.4
11
OM 2718

18.9 19.4 318 380 3.4
Average 2.9±0.9
Note: AG 24 is the variety taken at Kien Giang province and the rest are at Can Tho. The
average loss (%) of Kien Giang is 2.5 ± 1.9 and that of Can Tho is 3.3 ± 1.2 (confident level
95%).

Table 8: Influence of harvesting method on the grain losses due to shattering
Method of harvesting Shattering losses (%)
Hand 1.2-3.0
Reaper 0.7
Combined harvester 1.3-1.5









17





3.3 Estimation of harvesting losses
Harvesting losses consist of shattering and threshing losses. Therefore, a combination of data
in Tables 5 and 8 provide a picture of average harvesting losses. Table 9 shows that harvesting
losses can be as high as 4.4%. A threshing loss of 1.0% of combined harvester was estimated
by the manufacturer. On an average, mechanical harvesting reduced harvesting losses.
Table 9: Effect of harvesting methods on the harvesting losses
Harvesting method
Shattering
losses (%)

Threshing
losses (%)
Harvesting
losses (%)
Hand and heaped immediately 1.4 2.6-4.4
Hand
Hand and dried in the sun (one
day)
1.2-3.0
1.2 2.4-4.2
Reaper and heaped
immediately
1.1 1.8
Reaper
Reaper and dried in the sun
(one day)
0.7
0.8 1.5
Combined
harvester
1.3-1.5 1.0 2.3-2.5


Conclusion and project intervention methods:
• Shattering loss due to harvesting method and also due to time of harvesting
(particularly late harvesting) is an important factor to consider to reduce the grain losses
during harvesting.
• Machine threshing is beneficial in terms of quick harvesting of the crop; however it can
affect the head rice recovery due to some increase in rice cracking. Therefore, the
farmers and thresher operators should be aware of this effect in order to make them

more cautious on smooth operation.
• As a general trend above results demonstrate that the mechanical harvesting can reduce
the losses by more than half of the losses incurred during traditional harvesting method.
• The information will be communicated to the farmers through training sessions

18













APPEDIX 1


19
REPORT OF EXPERIMENT IN TÂN THỚI 1 COOPERATIVE
PHONG ĐIỀN - CẦN THƠ PROVINCE (Feb 2007):
Effect of harvesting time on kernel cracking
Truong Vinh, Tran Nguyen Ha Trang, Nguyen Thanh Phong, Le Hong Phuong,
Doan Kim Son, Pham Huynh Thai Son
1. Objective
The objective of this experiment is to determine the effect of harvesting time on kernel

cracking, and optimize harvesting period of some rice varieties, in Summer-Spring season in
the MRD.
2. Experimental time and place
¾ Time: Spring – Summer season from Feb 06
th
to Feb 19
th
2007.
¾ Place: Tan Thoi 1 cooperative, Can Tho province.
3. Materials and Method
3.1 Material and Instruments
¾ Variety OM2718: physiological maturity time is 90-92 days.
Variety OM1490: physiological maturity time is 90-92 days.
¾ Sample tray dryer ( 5kg/batch)
¾ Kett grain moisture content tester
¾ 1 kg plate balance
¾ Dry and wet-bulb thermometer
¾ 50 m ruler
¾ Plastic wire, picket.
¾ 10kg rice bags
¾ 1 kg sample bags
¾ Laboratory hulling, whitening and grading machines.

3.2 Method
The experimental design consisted of the treatments corresponding to the harvesting
times prior and after maturity date of selected rice varieties. The maturity date is defined as the
harvesting date planned by the farmer which is fitted well the physiological maturity time
given by the extension center. Samples were pretreated before being transferred to lab for grain
cracking test. Rice cracking level caused of harvesting time was evaluated based on statistical
data.

3.3 Experiments
3.3.1 Experimental Design
The experiment consisted of 7 treatments, six days prior and six days after maturity date
(MD) with a two-day interval. Time was the main factor of the experiment. Experiments were
designed in RCBD method. Each treatment had 5 blocks, corresponding to the number of
replications of each treatment. Details of the treatments are shown in Table 1.

20


Table 1: Treatments in relation to the maturity date
Treatment 1 2 3 4 5 6 7
Days vs. MD -6 -4 -2 0 +2 +4 +6

3.3.2. Experiment Procedure

Rice field selection and blocking design

Cutting

Threshing

Cleaning

Grain moisture contain determination

Packing

Transfering into room

Drying at low temperature

Packing, samples coding

Transferring into lab

Cracking testing

Figure 1: Flow chart for steps of harvesting time experiment

* Rice Field Selection and Block Design
From the need of rice samples for determination of physical properties as well as other
quality aspects, total requirement land was estimated to be 170m
2
for each variety.

21
The area for sampling was 70m
2
, the left area was for protective borders and walking
ways.
Blocks were designed according to the slope direction of land. Table 2 gives the sample
codes of the experimental units corresponding to their positions in field.
Table 2: Sample codes of the experimental units in field.

Block
Treatment
A B C D E
1 -6A -6B -6C -6D -6E

2 -4A -4B -4C -4D -4E
3 -2A -2B -2C -2D -2E
4 0A 0B 0C 0D 0E
5 +2A +2B +2C +2D +2E
6 +4A +4B +4C +4D +4E
7 +6A +6B +6C +6D +6E

• Cutting, threshing and cleaning
Cutting and threshing must be done manually. A sickle was used to cut rice stalk.
Rice was harvested in the morning to avoid intense sun light, aiming to reduce natural
cracking due to sudden change of moisture distribution inside the kernel when it goes between
wet night and dry day.
After cutting, rice was transferred into shadow for threshing and cleaning manually.
Cleaning of grain involves the separation of bulk straw, chaff, immature grain, and very
light and fine impurities from the grains. The straw and chaff were manually separated and the
grain was dropped though a cross-wind to remove the lighter impurities.
• Grain moisture contain determination
Cleaned grains were determined initial moisture content using Kett tester immediately in
the field. Samples were packed and brought back home for drying.

22

• Drying at low temperature
- Paddy samples from harvested blocks were gently dried at 35
0
C. Sample of each block
was spread out on two 50cm x 100cm trays of laboratory tray drier to ensure a very thin layer
of paddy on the surface of each tray.
- Ambient temperature was recorded prior to drying using a Dry and Wet-bulb
Thermometer.

- Check the grain moisture content every two hours.
- Dry until 14% grain moisture content.
- After being dried, samples were cleaned again to remove residual immature grains, then
measured for moisture content, packed into nylon bags and transferred to the lab for analysis.

• Cracking Determination
- Cracking determination before milling (natural cracking)
This is the direct indicator for effects of harvesting time on cracking.
Three 150g paddy samples were taken from each block to ensure the repetition of each
block. Grains were dehulled by hand.
Fifty dehulled grains were checked to count cracking grains under microscope. The cracking
fraction was calculated over fifty grains.

- Cracking determination after milling
Three 150g paddy samples were taken from each block to ensure the repetition of each
block. Each 150g sample was dehulled by laboratory huller to obtain brown rice. All by-
products were separated out of brown rice and their rates were counted by total input paddy.
100g brown rice from hulled rice was fed into a whitener to get white rice.
Then, white rice was graded by a rice grader to separate head rice, broken rice, and bran
from each other. Subsequently, fifty white head rice grains were analysed by microscope to
count number of cracking and chalkiness. Those percentages were calculated by dividing
counted number to total head rice grains (50)
Based on the milled and laboratory data, the percentage of total rice and head rice recovery
for each variety of paddy were calculated, and all calculations were subjected to statistical
analysis.

4. Data Processing
• All caculations were based on statistic analysis.
• Data was processed by Stasgraphics 3.0 software

5. Result and Discussion
5.1. Natural cracking fraction (NCF)
The average natural cracking fractions before milling are shown in Table 2 and ,Figure 1 and 2.
Table 2. The average natural cracking fractions before milling
Grain Cracks %
Variety
-6 -4 -2 0 +2 +4 +6

23
OM2718
2.4
a
0.67
a
6.27
b
2
a
3.2
a
7.2
b
8.53
b
OM1490
1.87
c
0.53
c
2.27

c
2.8
c
5.6
c
14.4
d
22.4
e
Values with different letters in a row represent significant difference (P<0.05)
8.53
9.00
7.20
8.00
6.27
6.00
7.00
Gain cracks (%)
5.00
3.20
4.00
2.40
3.00
2.00
2.00
0.67
1.00
0.00
0
-6 -4 -2 +2 +4 +6

Harvesting time (days from maturity)

Figure 1. Natural Cracking fraction of variety OM2718 versus Harvesting time

25.00
22.40
20.00
15.00
14.40
10.00
5.60
5.00
2.80
2.27
1.87
0.53
0.00

0
-6 -4 -2 +2 +4 +6
Harvesting time (days from maturity)
Grain Cracks (%)

Figure 2. Natural Cracking fraction of variety OM1490 versus Harvesting time


Figure 1 shows that there is a sharp increase of NCF of OM2718 in samples of 2, 4, and 6 days
after the MD. Natural cracking fraction (NCF) reaches a maximum of 8.53% in the 6 days after
the MD, a percentage four times higher than that of at MD, 2.0%. It can be seen, therefore, an
increasing trend of NCF by time after the MD.

For variety OM1490, the trend shown above was much clearer. On MD, the NCF was just
2.8% while that is 5.6, 14.40, and 22.40% respectively, for 2, 4, and 6 days after MD,
respectively. Especially, the 6-days after MD percentage is eight times greater than that at MD.
Meantime, there was not any trend for samples of treatments before MD. However, it can be
clearly seen from Figure 1 of OM2718 that NCF suddenly changes two days before MD at
6.27%. This increase can be attributed to the weather on the day havesting that treatment,
specifically cloudy at night before and extremly dry in following day.
Results from ANOVA analysis showed that NCFs at different harvesting time of both varieties
are, statistically, significant difference with confident interval of 95% (P<0.05). Plot position in
field did not affect these cracking fractions.

24
In general, the NCFs of treatments after the MD were higher than those before MD. The result
also indicated that variety OM1490 had higher NCF than that of variety OM2718.

5.2.Relative Head Rice Yield (RHRY)
The average of relative recovery HRY of each treatment is described in Table 3 and Figure 3
and Figure 5 .
Table 2. The average relative recovery

HRY %
Variety
-6 -4 -2 0 +2 +4 +6
OM2718
1.002
a
0.993
a
0.984
a

1
a
0.981
a
0.946
b
0.923
b
OM1490
0.93
de
0.975
e
0.986
e
1
e
0.951
de
0.887
cd
0.83
c
Values with different letters in a row represent significant difference (P<0.05)

1.02
1.002
1.000
0.993
1.00

0.984
0.981
RHRY
0.98
0.96
0.946
0.94
0.925
0.92
0.90
0.88
0
-6 -4 -2 +2 +4 +6
Harvesting time (days from maturity)

Figure 3. The relative head rice yield Vs Harvesting time of variety OM2718

67.63
67.01
66.40
67.48
66.22
63.81

62.41
59.00
60.00
61.00
62.00
63.00

64.00
65.00
66.00
67.00
68.00
69.00
+4 +6 -6 -4 -2 +2
0
Harvesting time (days from maturity)
HRY (%)

25
Figure 4. The head rice yield Vs Harvesting time of variety OM2718


1.20
1.000
0.986
0.975
0.951
RHRY
1.00
0.930
0.887
0.830
0.80
0.60
0.40
0.20
0.00

0
-6 -4 -2 +2 +4 +6
Harvesting time (days from maturity)

Figure 5. The relative head rice yield Vs Harvesting time of variety OM1490

80
67.90
66.93
66.21
63.13
64.57
70
60.25
56.35
60
50
40
30
20
10
0
-6
-4 -2 +2 +4 +6
0
Harvesting time (days from maturity)
HRY %

Figure 6. The head rice yield Vs Harvesting time of variety OM1490

Values with different letters in a row represent significant difference (P<0.05)

Figures 3 and 5 show that the Relative Head Rice Yield always reaches maximum at the MD
and decreases at other treatments for both variety OM2718 and OM1490. RHRY goes down to
minimum value of 0.83 and 0.925 for OM1490 and OM2718 respectively, at the six days after
MD treatments. It is obvious that HRY decreased by late harvesting time. It is compatible with
the results of Natural Cracking fraction as described above.

26
Results from ANOVA analysis showed that HRYs, at different harvesting time of both
varieties, were statistically significant different with confident interval of 95% (P<0.05). Plot
position in field did not affect these results with confident interval of 95% (P>0.05).

5.3. Cracking fraction after milling
The cracking fraction after milling of each treatment was described in Table 4, and Figure 7
and Figure 8.
Table 4. The cracking fraction after milling
Brown rice cracking fraction, %
Variety
-6 -4 -2 0 +2 +4 +6
OM2718
0.33
a
1.83
a
0.13
a
0.67
a
0.53

a
1.8
a
6.60
b
OM1490
0.33
c
1.33
c
3.87
d
2.07
cd
6.67
e
10.13
f
13.47
g
Values with different letters in a row represent significant difference (P<0.05)
6.60
7.00
6.00
5.00
4.00
3.00
1.83
1.80
2.00

0.67
0.53
1.00
0.33
0.13
0.00
-6
+6
0
-4 -2 +2 +4
Harvesting time (days from maturity)
Grain Cracks (%)

Figure 7. Cracking fraction Vs Harvesting time of variety OM2718


27
16.00
13.47
14.00
12.00
10.13
10.00
8.00
6.67
6.00
3.87
4.00
2.07
1.33

2.00
0.33
0.00
0
-6 -4 -2 +2 +4 +6
Harvesting time (days from maturity)
Grain Cracks (%)

Figure 8. Cracking fraction Vs Harvesting time of variety OM1490

Figures 7 and 8 highlight the common trend of cracking fraction for both varieties. There is a
sharp increase of cracking fraction after milling. The optimums were reached in the six days
after MD treatments, 13.47%, 6.6% for OM1490 and OM 2718 respectively. It reflected the
fact that after MD, the more delayed harvesting time was, the higher cracking fraction.
However, before MD those percentages fluctuated without any trend. This can be attributed to
the unstable structure of grain before physical maturity.
Results from ANOVA analysis show that Cracking fractions of different treatments of both
varieties are statistically significant different with confident interval of 95% (P<0.05). Block
factor did not affect the experimental result.

5.4. General comments for all experiments.
- Common trend: the experimental results for both variety OM2718 and OM 1490
demonstrated the effect of harvesting time on rice cracking. After the MD, rice cracking
increased by harvesting time, which resulted in low head rice recovery.
- There had some fluctuation of cracking fraction by time before the MD, but those
changes did not follow any rule. It can be understood that grains were not mature
enough, and inside structure of grains were still unstable before MD.

28
- The differences of Cracking fraction and Head rice Recovery of different treatments,

on the same variety, were significant with confident interval of 95% (P<0.05). Plot
position did not affect experimental result.
- For variety OM2718: according to survey data, the life time of rice at MD was 92 days,
one day later than its average physiological maturity (90-92 days). However, low
cracking fraction and high head rice recovery at MD confirmed the right decision of
farmers at harvesting time. Therefore, harvesting after 93 days would accelerate
cracking rate and reduce the head rice recovery.
- For variety OM1490: it was the same with variety OM2718.


29