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

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.. 1.1.1 Cracking in brown

SECTION 1

OPTIMAL HARVESTING METHODS TO REDUCE GRAIN LOSSES

(RAINY 2006 AND DRY SEASONS 2007)

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)

Season Locations Rice variety Harvesting

period

Rainy Tan Thoi 1 cooperative,

Can Tho province

OM 2718, OM1490

30May-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

Dry Tan Thoi 1 cooperative,

Can Tho province OM1490 OM 2718, 6-19Feb 2007 Dry Tan Phat A cooperative,

Kien Giang province

OM2517, OM4498

6-19Feb 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

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

0.80 3.20

9.60 4.80 10.80 15.20 23.60

0 2 4 6 8 10 12

0.13 0.67

1.6 0.4 0.53 1.34 1.33 1.73

0 2 4 6 8 10

-3 -2 -1 0 +1 +2 +3 Harvesting time (days from maturity)

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

-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

6.27

2.00 3.20

7.20 8.53

0.00 1.00 2.00 3.00 4.00 5.

10.00

5.60 5.00 2.27 2.80

4.40 6.00

0 2 4 6 8 10 12

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

12.2

0 2 4 6 8 10 12 14

-3 -2 -1 0 +1 +2 +3 Harvesting time (days from maturity)

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

1.80 1.83

2.00

0.67 0.531.00 0.33 0.13

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

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 %

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

An Giang (24) 0.3-1.5 0.5-4.2 Rainy

0 5 10 15 20 25 30 35 40 45 50 55

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

Variety: OM 2718 (Dry) Variety: OM1490 (Dry)

-3 -2 -1 0 +1 +2 +3 Harvesting time (days from maturity)

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)

63.81 62.41

1 2 3 4 5 6 7

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

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)

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

*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

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

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

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 (%)

Head rice recovery

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

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

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

Reaper 0.7

Combined harvester 1.3-1.5

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 Hand and dried in the sun (one

day)

1.2-3.0

1.2 2.4-4.2 Reaper and heaped

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

APPEDIX 1

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 06th to Feb 19th 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

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

Table 1: Treatments in relation to the maturity date

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 170m2 for each variety

The area for sampling was 70m2, 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

• 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

• Drying at low temperature

- Paddy samples from harvested blocks were gently dried at 350C 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 %

OM2718 2.4a 0.67 a 6.27b 2a 3.2a 7.2b 8.53b

OM1490 1.87c 0.53c 2.27c 2.8c 5.6c 14.4d 22.4e

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

2.40 3.00 2.002.00

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

0.53 0.00

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

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

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

0

Harvesting time (days from maturity)

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

+4 +6 -6 -4 -2 0 +2

Harvesting time (days from maturity)

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

1.20

1.000 0.986 0.975 0.951

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

56.35 60

50 40 30 20 10 0 -6 -4 -2 0 +2 +4 +6 Harvesting time (days from maturity)

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

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, %

6.00 5.00 4.00 3.00

16.00

13.47 14.00

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

- 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

APPENDIX 2

REPORT OF EXPERIMENT IN TAN PHAT A COOPERATIVE

KIÊN GIANG 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, Mai Huynh Cang, Nguyen Huu Anh Tuan

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 06th to Feb 19th 2007

¾ Place: Tan Phat cooperative, Kiên Giang province

3 Materials and Method

3.1 Material and Instruments

¾ Variety OM2517: physiological maturity time is 85-91 days

Variety OM4498: physiological maturity time is 90-95 days

¾ Sample tray dryer ( 5kg/batch)

¾ Kett grain moisture content tester

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

Table 1: Treatments in relation to the maturity date

Transfering into room

Drying at low temperature

Packing, samples coding

Transfering 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 170m2 for each variety

The area for sampling was 70m2, 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

• 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 content determination

Cleaned grains were determined initial moisture content using Kett tester immediately in the field Samples were packed and brought back home for drying

• Drying at low temperature

- Paddy samples from harvested blocks were gently dried at 350C 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 the 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 fractions were calculated based on total input paddy

100g brown rice was taken for whitening to get white rice

Then, white rice was graded by a rice grader to separate head rice and broken rice from each other Subsequently, fifty white head rice grains were analysed by microscope to count the number of cracks 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 calculations were based on statistical analysis

• Data was processed by Statgraphics 3.0 software

6 Result and Discussion

5.1 Natural cracking fraction (NCF)

The average natural cracking fractions before milling are shown in Table 2 and Figures 2 and

70.00 60.53 60.00

50.00

33.60 40.00

30.00

16.00 20.00

8.00 6.00 3.73

Harvesting time (days from maturity)

Figure 3 Natural Cracking fraction of variety OM4498 versus Harvesting time

Figure 2 shows that for variety OM2517, the NCF is just 5.73% while that is 16.0; 33.60; and 60.53% respectively, for 2, 4, and 6 days after MD Especially, that percentage at 6 days after

MD is eleven times higher than that at MD This meant that after MD, cracking fraction increased by late harvesting time However, this trend was not clear for the Variety OM4498 (Figure 3) There was a slight reduction of NCF at 2 days after MD, 1.07% against 1.47% at

MD But at 4 days after MD, the NCFs rose up dramatically The NCF of 6 days after MD was six times higher than MD

Results from ANOVA analysis showed that NCFs 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 cracking fractions

In general, the NCFs of treatments after the MD were higher than those before MD The result

also indicated that NCF of OM2517 was higher than that of OM4498

5.2 Head Rice Yield (HRY) and Relative Head Rice Yield (RHRY)

As we are now using a local laboratory milling system, the testing procedure should be

standardized For a standard milling system such as SATAKE, the whitening time is 1 minute

It was found that in our system , 1 minute was not enough to remove the bran layer The head

rice recovery depends strongly on the whitening time and variety This problem will be studied

systematically and reported next time Thus, due to the uncertainty of the HRY, the relative

HRY was introduced to get more convenient on discussion the results The relative HRY is the

ratio between HRY of a treatment and HRY of samples at maturity The average of relative

HRY of each treatment is described in Table 3 and Figures 4 and 6 The HRY is shown in

1.000 0.938 1.00

0.725 0.80

0.505 0.60

0.40 0.20 0.00

70.00 64.58 60.00 56.68 53.1850.00 45.19 43.74

41.09

40.00

28.63 30.00

20.00 10.00 0.00

-6 -4 -2 0 +2 +4 +6

Harvesting time (days from maturity))

Figure 5 The head rice recovery Vs Harvesting time of variety OM2517

Figures 4 and 5 show the Relative HRY and Head Rice Recovery of OM2517 variety It could

be seen that there had large variations among HRY of different treatments There was a

conclusion from this experiment for both varieties, OM2517 and OM4498, that the Head Rice Recovery reached maximum at MD and steadily went down at treatments around MD It is obvious that HRY decreased by late harvesting It is compatible with the results of Natural

Cracking fraction as described above

1.20

1.000 0.976 0.922

1.00 0.751 0.80

0.60 0.40 0.20 0.00

+6 0

58.33 56.9560.00 54.35 54.02 53.78 52.5550.00 43.80

40.00 30.00 20.00 10.00 0.00

-6 -4 -2 0 +2 +4 +6

Harvesting time (days from maturity)

Figure 7 The head rice recovery Vs Harvesting time of variety OM4498

Results from ANOVA analysis showed that HRYs at different harvesting time of both varieties were, statistically, significant difference 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 Figures 8 and 9

Table 4: The cracking fraction after milling

Cracking fraction of brown rice (%)

OM2517 1.2a 35.33c 5.60a 5.40a 8ab 9.33ab 17.20b

OM4498 20.40e 5.33d 7d 3.87d 6.4d 8.07d 7.53d

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

From Table 4, Figures 8 and 9, it was noticed that there were dramatic differences of the cracking fraction of 4 days prior MD for OM2517 and 6 days prior MD for OM4498 It reached 35.33% and 20.04%, respectively However the change of cracking fraction of post-

MD samples still followed the rule of cracking increasing by late harvesting This fact indicated that harvesting after MD had bad effect on cracking fraction

40.00 35.33

30.00 35.00

25.00

17.20 15.00

20.00

9.33 8.00

Figure 8 Cracking fraction Vs Harvesting time of variety OM2517

Figure 9 Cracking fraction Vs Harvesting time of variety OM4498

Results from ANOVA analysis showed that cracking fractions of different treatments of both varieties were, statistically, significant difference with confident interval of 95% (P<0.05) Block factor did not affect the experimental results

5.5 The general comments for all results

- Common trend: the experimental results for both variety OM2517 and OM4498 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

1.20

5.60 5.405.00

8.07

5.33

3.87 5.00