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

SECTION 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 different varieties in 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 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 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 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 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 days prior and days post-maturity stages in days intervals (except 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 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 and 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 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), Harvesting at optimum harvest time had rather small cracking problem but delay of days can cause major problem (and hence intervention opportunity here) 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 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 23.60 20 10.80 9.60 12 4.80 3.20 0.80 10.80 10 15.20 16 12 Grain cracks (%) Grain cracks (%) 24 5.20 4.00 2.80 -6 -4 -2 +2 +4 0.40 0.40 -6 -4 +6 Harvesting time (days from maturity) 20.00 14.40 15.00 Grain cracks (%) Grain cracks (%) 22.40 10.00 5.60 1.87 0.53 2.80 9.00 8.00 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00 -4 -2 +2 +4 Harvesting time (days from maturity) 2.00 0.67 -4 -2 +2 +6 Variety: OM 2718 (Dry) 8 5.47 0.67 +4 Harvesting time (days from maturity) 1.6 0.4 0.53 -1 1.34 1.33 1.73 Grain crack s (% ) Grain cracks (%) 3.20 2.40 10 0.13 +6 6.27 -6 10 +4 8.53 +6 Variety: OM 1490 (Dry) 8.66 5.18 -2 5.14 3.92 -3 7.6 -4 -3 -2 +1 +2 +3 +4 Harvesting time (days from maturity) +1 +2 +3 Variety: Jasmine (Rainy) 60.53 Grain cracks (%) 70.00 60.00 50.00 40.00 30.00 20.00 10.00 1.47 0.00 -6 -1 Harvesting time (days from maturity) Variety: An Giang 24 (Rainy) Grain cracks (%) +2 7.20 0.00 -6 Variety: OM 2718 (Rainy) 25.00 2.27 -2 Harvesting time (days from maturity) Variety: OM 1490 (Rainy) 5.00 1.20 33.60 16.00 2.00 3.60 5.73 -4 -2 8.00 6.00 4.00 3.73 +2 +4 +6 2.93 1.07 2.00 Harvesting time (days from maturity) Variety: OM2517 (Dry) 9.33 10.00 1.47 1.47 1.07 -4 -2 +2 0.00 -6 +4 +6 Harvesting time (days from maturity) 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 (+ days) than the predicted day of maturity 11.60 12 12 10 Grain cracks (%) Grain cracks (%) 10 4.40 4.40 4.40 5.20 4.80 1.60 6.00 4.40 2.80 -6 -4 -2 +2 +4 +6 -6 -4 Grain cracks (%) Grain cracks (%) 12.00 10.13 10.00 6.67 2.07 1.33 5.00 4.00 3.00 0.33 -2 +2 +4 -6 +6 -4 4.13 -3 0.4 0.53 -1 1.07 1.27 +1 +2 1.73 Grain crack s (% ) Grain cracks (%) -4 14 12 10 -2 +3 7.4 +6 -2 -1 9.4 +4 +1 +2 +3 Harvesting time (days from maturity) Variety: Jasmine (Rainy) Grain cracks (%) Variety: An Giang 24 (AG 24) (Rainy) 40.00 35.33 35.00 30.00 25.00 17.20 20.00 15.00 8.00 9.33 10.00 5.60 5.40 5.00 1.20 0.00 -6 -4 -2 +2 +4 +6 Harvesting time (days from maturity) 12.2 8.4 7.8 Harvesting time (days from maturity) Variety: OM2517 (Dry) +4 11.8 -3 Grain cracks (%) +2 Variety: OM 2718 (Dry) 10 1.47 -2 Harvesting time (days from maturity) Variety: OM 1490 (Dry) 0.67 0.53 0.00 -4 0.27 0.67 0.13 Harvesting time (days from maturity) 1.80 1.83 1.00 0.00 -6 6.00 2.00 3.87 0.33 +6 6.60 7.00 13.47 14.00 2.00 +4 Variety: OM 2718 (Rainy) 16.00 4.00 +2 Harvesting time (days from maturity) Variety: OM 1490 (Rainy) 6.00 0.40 Harvesting time (days from maturity) 8.00 -2 3.20 2.40 1.60 25.00 20.00 20.40 15.00 10.00 5.33 5.00 7.00 3.87 6.40 8.07 7.53 0.00 -6 -4 -2 +2 +4 +6 Harvesting time (days from maturity) 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 (+ days) than the predicted day of 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 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 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 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 Head rice recovery relative % Before maturity Rainy Proportion of cracked grain % Before maturity After maturity After maturity 106-109 72-88 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 2.4-6.3 3.2-8.5 93-99 83-95 OM2517 1.5-3.6 16-60.5 80-114 51-94 OM4498 Rainy 10.8-23.6 OM2718 Dry 0.8-9.6 OM2718 Dry OM1490 1.5-3.7 1.1-9.3 75-93 90-98 0.5-1.6 1.3-5.1 93-97 83-108 4-4.5 6-7.7 75-99 87-99 An Giang (24) Jasmine 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 Season Rice variety Proportion of cracked grain % Before maturity Dry 5.2-6.1 7.2-11.6 0.4-2.8 3.2-6.0 OM1490 0.3-3.9 6.7-13.5 OM2718 Dry OM1490 OM2718 Rainy After maturity 0.1-0.3 0.5-6.6 OM2517 1.2-5.6 8-17.2 OM4498 5.3-20.4 6.4-7.5 11 0.3-1.5 0.5-4.2 0.4-2.8 3.2-6.0 51.47 45.41 43.91 43.54 38.76 -6 -4 -2 +2 40.72 36.83 +4 Head Rice Recovery (%) 55 50 45 40 35 30 25 20 15 10 An Giang (24) Jasmine Head Rice Recovery (%) Rainy 52.3 51.06 55 50 45 40 35 30 25 20 15 10 36.51 -6 +6 -4 67.01 67.48 80 66.40 66.22 66.00 65.00 63.81 64.00 62.41 63.00 62.00 61.00 60.00 59.00 -6 -2 -4 +2 +4 70 63.13 -2 -1 67.90 64.57 60.25 56.35 40 30 20 10 -4 -2 +4 +2 +6 Harvesting time (days from maturity) Variety: OM1490 (Dry) 46.33 46.99 42.72 60 55 50 45 40 35 30 25 20 15 10 54.65 +1 +2 +3 55.36 51.82 54.59 48.15 49.46 +2 +3 41.59 -3 -3 +6 50 -6 35.9 -4 +4 +6 Head Rice Recovery (%) Head Rice Recovery (%) 43.5 +2 60 Variety: OM 2718 (Dry) 42.35 41.75 40.76 42.51 66.93 66.21 Harvesting time (days from maturity) 55 50 45 40 35 30 25 20 15 10 0 Variety: OM1490 (Rainy) Head Rice Recovery ( %) Head Rice Recovery ((%) 67.63 67.00 -2 34.53 Harvesting time (days from maturity) Variety: OM 2718 (Rainy) 68.00 47.99 42.23 Harvesting time (days from maturity) 69.00 50.73 -2 +4 -1 +1 Harvesting time (days from maturity) Harvesting time (days from maturity) Variety: An Giang (24) (Rainy) Variety: Jasmine (Rainy) Head Rice Recovery % 56.68 60.00 50.00 41.09 53.18 45.19 43.74 40.00 28.63 30.00 20.00 10.00 Head Rice Recovery % 70.00 70.00 64.58 60.00 50.00 54.35 54.02 -4 -2 58.33 56.95 +2 53.78 52.55 +4 +6 43.80 40.00 30.00 20.00 10.00 0.00 0.00 -6 -4 -2 +2 +4 +6 Harvesting time (days from maturity) Variety: OM2517 (Dry) -6 Harvesting time (days from maturity) Variety: OM4498 (Dry) 12 Figure 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: 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 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 With the two varieties investigated in two seasons (wet and dry), the seasonal effect was not found significant 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 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) 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% 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: Hand (+ mechanical threshing) Reaper (+mechanical threshing) 13 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 TanThoi co-operative, CanTho (OM 2718, OM1459) GoGon co-operative, LongAn (Bu Tin, VN 95-20) Harvesting method Hand and heaped immediately Hand and dried in the sun (one day) Reaper and heaped immediately Reaper and dried in the sun (one day) Hand and heaped immediately Hand and dried on the sun (one day) Combined harvester Average Head Notation rice recovery (%) HH 41, 50 HD 37, 47 RH 49* RD 52* HH 45, 60 HD 43, 62 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 14 F1TT6A F1TT6B F1TT6C F1TT6D F1TT6E F1TT7A F1TT7B F1TT7C F1TT7E F1TT7E • 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, aimed 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 grain The straw and chaff was manually separated and the grain was dropped though a cross wind to remove the lighter impurities • Grain moisture contain determination Cleaned grain was determined initial moisture contain by Kett tester immediately in the field Samples were packed and brought back home for drying • Drying at low temperature Paddy samples from harvest blocks were gently dried at 350C in 24h Sample of each block was spread out on two 50cm x 100cm trays of laboratory tray drier, ensured a very thin layer of paddy on the surface of each tray Ambient temperature was recorded prior to drying by means of dry and wet-bulb thermometer After being dried in 24h, samples were cleaned again to remove left immature grains, then measured moisture contain, packed by nylon bags and transferred into lab for analysis All of experiment was implemented in 14 days from May 30th to June 13th 2006 • Cracking Determination Three 150g paddy samples were taken from each block to ensure the repetition of each block Each 150g sample was hulled by SAKATE 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 whitener to get white rice Then white rice was graded by SAKATE grader to separate head rice, broken rice and bran from each other Fifty grains of head brown rice were picked randomly to count cracking grains by a microscope The cracking fraction was calculated over fifty grains For white rice, fifty head rice grains were also picked up from white and graded head rice to count number of cracking and chalky kernels Those percentages were calculated by dividing counted number to total head rice grains (50) Base 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 3.3.3 Data Processing • All caculations were based on statistic analysis • Data was processed by Stasgraphics software 60 RESULT AND DISCUSSION 4.1 Rice cultivated structure Tan Thoi cooperative consists of 629 households, total land area of 320ha including ricecultivated area of 200ha It is divided into sections, e.g., section 1,2,3 with area of 120ha, 90 and 110ha respectively Survey was carried out at household in the sections and From the survey result (Annext B1) The varieties OM 2718 and OM 1490 occupied 35% and 39%, respectively These two varieties were selected for experiment.The summary result is illustrated in Figure 50 40 39 35 RATE % 30 25 20 10 O M 2718 O M 1490 Figure 1: Varieties cultivated structure chart O T HER S V A R IE T IE S Data from the survey showed that: - Most farmers were trained about cultivated method So their ways of using fertilizer, irrigation, chemical, etc were nearly the same - Low productive due to lack of water for irrigation - Most households did not harvest on time From the survey result, the varieties OM 2718 and OM 1490 were selected for experiment After choosing the proper variety, rice field was bought and experimented as following procedure: Two varieties OM 2718 OM 1490 Seven treatment samples Cutting, stripping, cleaning MC determination Drying at 350C in 24 h Cracking determination Figure 2: Flowchart described the procedure for harvesting time experiment 4.2 RESULT 61 4.2.1 Cracking rate of brown rice By experiment process and sample analysis, cracking rate of brown rice of each treatment on two varieties were illustrated in Table and Table 2: average percentage of brown cracking rate on two experimental varieties Variety OM2718 OM1490 F1TT1 0.4a 0.8e F1TT2 0.4a 3.2e Cracking rate of brown rice % F1TT3 F1TT4 F1TT5 a a 1.2 2.8 10.8b 9.6f g 4.8ef 10.8f g F1TT6 4a 15.2g F1TT7 5.2ab 23.6h Note: average treatments followed by the same letter are statistically insignificant difference with confident interval of 95% (P