Project Completion Report:" Investigation of rice kernel cracking and its control in the field and during post-harvest processes in the Mekong Delta of Vietnam - MS4 " docx

180 Ministry of Agriculture & Rural Development Project Completion Report MS14: PROJECT COMPLETION REPORT 026/05VIE Investigation of rice kernel cracking and its control in the field and during post-harvest processes in the Mekong Delta of Vietnam APPENDIX 8A EXTENSION WORKERS MANUAL-PART 1 IMPROVING FARMER’S PROFITABILITY BY MINIMIZING GRAIN LOSS AND MAINTAINING QUALITY THROUGH CORRECT PROCEDURES DURING HARVESTING AND POST- HARVEST OPERATIONS 181 INTRODUCTION Reduced whole rice grain yield and value due to cracking is one of the major issues that directly reduce income and availability of staple food to the farmers in the Mekong River Delta. The cracking or partial fissuring of rice kernels may occur right in the paddy field due to incorrect harvesting time/practice, improper post-harvest drying conditions and inappropriate milling operations. There is a chain of activities during harvesting and post-harvest processing of rice. Figure 1 is a diagram showing a post-production system of rice in the MRD of Vietnam currently. All chains in this system can contribute to losses. Some of the important factors can be dependent to each other. Here we consider two aspects: 1. Grain loss (G): Harvesting and post-harvesting losses in which grain is not fully recovered during a particular operation on farm 2. Value loss (V): Grain cracking and reduced head rice yield which result in downgrade in grain quality value, such as broken rice during milling. The value of rice might be reduced by 50% or less. Accordingly, the manual is divided into 4 sections in relation to: 1. Harvesting time, 2. Harvesting method, 3. Drying method, and 4. Milling Harvesting loss is relevant only in the first two sections, while the grain cracking and head rice yield are affected by activities during the harvesting as well as post-harvest. The main factors which contribute to the rice cracking and value losses are: • Harvesting time- before and after grain maturity • Harvesting methods- manual, reaper, combined harvester • Drying methods- sun drying and mechanical drying • Milling losses- small, medium, large rice milling plants and milling procedure. 182 Types of Losses Harvesting Time At the mature date G After the mature date G+V Method Manual cutting + Hand collecting + Mechanical Threshing Reaper + Hand collecting + Mechanical Threshing G+V Reaper + Combined-Collector (collecting + threshing) Combined-Harvester Transportation G Drying Field drying G+V Sun drying G+V Mechanical drying Correct G Incorrect G+V Transportation G Storage V Transportation G Milling Small scale V*** Medium scale V** Large scale V* Figure 1: Post-production system of rice in the Mekong River Delta of Vietnam and loss components. G is grain loss, V is value loss, *, ** and *** signs indicate relative degree of losses. 183 SUMMARY OF POST-HARVEST LOSSES Table 2 is the summary of total post-harvest losses (Table 2) based on the data collected in the past two years from Mekong Delta region. In this table, the values are the overall estimation from different varieties. The values presented are in the relative term between the cases. For instance, late harvesting has 3.5% of losses in comparison to harvesting at correct time. The value loss at correct harvesting time is considered to be 0%. • From the milling survey data, an average milling quality system caused a value loss of about 4% in comparison to a good quality system which was considered to be 0% value losses. • Experimental data of flat-bed drying gave that incorrect drying procedure resulted in 5% value losses in comparison to correct case which was considered to be 0% value losses. • Sun drying of panicle means that paddy after cutting was left in the field for sun drying (field drying). The value losses of 8.7% and 4% of field drying and sun drying on yard, respectively, were the relative values compared to correct drying procedure. Table 2: Overall evaluation of total post – harvest losses (late harvesting, moderate milling quality) Harvesting time Harvesting method Threshing Sun drying Drying Milling Total (%) Panicle(V=8.7%) 13.1 Yard(V=4%) 8.4 Correct(0%) 4.4 Manual/ Reaper (G=2.9%) Yes (V=1.5%) Incorrect (V=5%) 9.4 Yard(V=4%) 6.7 Correct(0%) 4.2 Correct (V=0%) Combined- Harvester (G=1.2% V = 1.5%) No (0%) Incorrect (V=5%) Good quality (0%) 7.9 Panicle(V=8.7%) 20.6 Yard(V=4%) 15.9 Correct(0%) 11.9 Manual/ Reaper (G=2.9%) Yes (V=1.5%) Incorrect (V=5%) 16.9 Yard(V=4%) 14.2 Correct(0%) 10.2 Late (V=3.5%) Combined- Harvester (G=1.2% V = 1.5%) No (0%) Incorrect (V=5%) Average quality (4%) 15.2 Note: V= Value losses, G = Grain losses. There are three cases of losses that can be highlighted in Table 2. 1. The highest total losses is 20.6% including late harvesting (3.5%), manual cutting (2.9%), threshing (1.5%), field drying (8.7%), incorrect drying procedure (5%) and using average milling quality (4%). 2. The common cases of total losses are in the range of 12.4 to 15.9% including correct (or late) harvesting time, manual cutting, threshing, sun drying on yard, average milling quality applied. 184 1. INFLUENCE OF HARVESTING TIME ON THE RICE CRACKING AND QUALITY LOSSES Physical grain losses during harvesting can be divided into various types, depending on the operation and the machinery used. Losses during cutting crops • Shattering loss: shedding of mature grains from the panicle caused by birds, wind, rats, and handling. • Lodging loss: plants with mature grains fall on the ground making the grains difficult to recover. • Standing crop loss: standing plants with mature grains are left standing in the field after harvesting. Losses during threshing and cleaning • Separation loss or “blower loss”: grains that are mixed with straw or chaff during the cleaning operation. • Scatter loss: grains that are scattered on the ground during the threshing and cleaning operation. • Threshing loss or unseparated loss: mature grains that remain attached to the panicle in the straw after completion of the threshing operation. Losses during crop and grain handling: • Handling loss: mature grain lost during lifting, hauling, stacking, pouring, and bagging of crop and grains. Incorrect time of harvesting increases harvest losses. The main problem is caused by delayed harvesting, as this increases susceptibility to shattering, lodging and standing crop losses. Incorrect harvesting time is also 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 correct time. Thus we need to identify the correct time for harvesting. Estimating the correct time of harvesting Recommended time of harvesting for each variety is estimated from the time of sowing in each season. Table 3 presents the estimated days from sowing to harvest for various varieties in MRD. 185 Table 3. Growing time recommended by extension center Variety Recommended growing time (day) Variety Recommended growing time (day) OM1490 87-92 OM2517 85-90 OM2718 90-95 IR50404 90-95 Jasmine 95-105 OM4498 90-95 AG24 85-90 While this is useful way to estimate correct harvesting time, each crop differs in the correct harvesting time, as some mature faster and others mature more slowly, e.g. crops affected by salinity. Thus more accurate date of correct harvesting time can be made with observation during growth of each crop. Probably the most common way is to estimate harvest time from the observation of heading date, and add number of days to allow duration for grain filling. In dry season, an optimum time of harvest is 28 to 35 days after heading. In wet season, optimum time is 32 to 38 days after heading. (This needs to be converted to Vietnamese seasons I will find the data and add to this paragraph) When the crop approaches the estimated optimum time of harvesting, then further observation is made to determine the exact time of harvesting. For harvesting the grain moisture content ideally is between 20-25% (wet basis). Grains should be firm but not brittle when squeezed between the teeth. However, in the Summer-Autumn season in Mekong Delta River, the moisture content is normally 28-30% due to frequent rains. This means that prompt drying of grain is very critical to avoid rice cracking, germination and fungal damage. At around this time, the crop should be cut when 80-85% of the grains are straw (i.e. yellow) coloured (see photograph). Harvesting also needs to be timed so that threshing can be done as soon as possible after cutting to avoid re-wetting and reduce grain breakage. Thus, combine-harvester is the best harvesting method. If the crop has a lot of surface moisture, e.g. from previous rainfall or early in the morning, it is advisable to wait to cut the crop until the surface moisture dries off. 186 From the experiments on 7 rice varieties in three seasons in the past 2 years (2006-2008), the optimal harvesting time to maximise head rice yield for each variety in each season (dry/rainy) is presented in Table 4. Most of the cases fell within the recommended day mentioned in Table 3. However, some cases were outside of this range such as OM2517 (94 days in rainy season), AG24 (94 days in rainy season) and OM2718 (88 days in rainy season). Table 4: Optimal growing time for highest HRY (coloured numbers are the optimal growing time for harvesting) Variety Season Growing time (day) Dry 88 90 92 94 96 98 OM1490 Rainy 88 90 92 94 98 104 Rainy 88 90 92 94 96 98 OM2718 Dry 88 90 92 94 96 98 Rainy 86 88 90 92 94 96 OM2517 Dry 82 84 86 88 90 92 Rainy 86 88 90 92 94 96 OM4498 Dry 87 89 91 93 95 97 Jasmine Rainy 94 96 98 100 102 104 AG 24 Rainy 86 88 90 92 94 96 IR50404 Rainy 88 90 92 94 96 98 Yield loss Correct timing of harvest is crucial in order to prevent crop loss. Grain losses may occur from rats, birds, crop lodging, insects, and shattering. Timely harvesting ensures good grain quality and high market value. Harvesting too early will result in a larger percentage of unfilled or immature grains, which will result in a lower yield and in higher grain breakage during milling. Harvesting too late will lead to excessive losses and increased breakage in rice. Grain cracking and head rice yield (HRY) The following figures (Figure 2 and 3) show the mean of grain cracking and also that of head rice yield among several varieties obtained in Mekong Delta during 4 seasons of experiments in 2006-2008. 187 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 Harves ting time (days from maturity) Head Rice Recovery (% ) 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: 1490 (Rainy season 2006) Variety: 2718 (Rainy season 2006) Figure 2: Effect of harvesting time on grain cracking. The X axis indicates days of early or late harvesting compared to maturity date (day 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 (% ) Variety:OM 1490 (Rainy season 2006) Variety: OM2718 (Rainy season 2006) Figure 3: Effects of harvesting time on head rice yield. The X axis indicates days of early or late harvesting compared to maturity date (day 0). Do Not harvest late after the maturity date in order to avoid cracking and to increase HRY 188 Table 5 summarises the losses due to late harvesting for different varieties harvested in different seasons of MRD in 2006-2008. The HRY is reduced by 5-28% if harvesting time was 6 days late. Assuming 1% of HRY reduction equivalent to 0.5% of losses (50% value loss), then late harvesting would cause a loss of 2.5-14%. The varieties AG24 and IR50404 had losses below 2.5%, whereas the varieties OM1490, OM2517 and OM2718 had high losses of above 5% (6 days late harvesting). Theses varieties need to be harvested earlier. Table 5: Losses of Head Rice Yield (HRY %) due to late or early harvesting. Variety Season Losses of HRY (%) in comparison to optimal harvesting time Dry/Rainy?? 0 1.57 4.31 10.07 15.79 17.77 OM1490 Rainy/Dry?? 1.69 0.97 0 3.33 7.65 11.55 Rainy 0 7.93 7.56 12.71 14.64 10.75 OM2718 Dry 0.47 1.08 0 1.26 3.67 5.07 Rainy 5.08 11.36 7.05 4.77 0 4.9 OM2517 Dry 15.59 11.5 0 3.5 12.94 28.05 Rainy 4.65 6.59 3.07 4.55 0 7.07 OM4498 Dry 17.24 13.15 0 1.38 4.55 5.78 Jasmine Rainy 0.71 3.54 0 0.77 7.21 6.2 AG 24 Rainy 6.23 4.48 3.49 0.66 0 4.27 IR50404 Rainy -0.25 0.89 0 5.97 1.29 2.16 Note: 0 is the optimal day. After (before) this day is late (early) harvesting. From one cell to the adjacent cell the harvesting time changed by two days. The survey data shows that most of the farmers were late harvesting by 1 to 3 days. For varieties, OM1490, OM2718, Jasmine and AG24 were harvested late by 80%, 90%, 55% and 50% of farmers, respectively. 1. The harvesting time is one of the important factors to control the rice cracking and eventual head rice recovery. There is a clear trend that a few days early harvesting (before maturity) is better than the late harvesting. 2. The same effect persists in rainy or dry season (check further data – more figures have been inserted to Figure 2 &3). 3. Varieties differ in their grain cracking and those with small cracking such as AG24 is recommended. When head rice recovery is also considered, OM4498 had smaller loss even it Field experiments indicated that: 4-6 days late harvesting increase cracking by up to 24%, and reduce HRY by up to 28%. 189 was harvested later than the optimum harvest time (Check data further). In one of the varieties tested in this investigation, a proportion of cracked rice was as high as 24%. The results have highlighted the importance of rapid harvesting of the crop. Farmers are encouraged to make their crop management in such a way that they can harvest earlier (e.g., organize labour for harvesting). This is expected to impact the farmers’ decision to determine the harvesting time. In addition, the farmers are encouraged to plant varieties with different maturities so that each crop can be harvested at the correct time of harvesting. There may also be some opportunities to plant at different times of the same variety, so that the harvesting is spread for a longer time period. However, the best option is to introduce mechanical harvesting (see Section 2). [...]... Development Project Completion Report MS14: PROJECT COMPLETION REPORT 026/05VIE Investigation of rice kernel cracking and its control in the field and during post-harvest processes in the Mekong Delta of Vietnam APPENDIX 8B EXTENSION WORKERS MANUAL-PART B IMPROVING FARMER’S PROFITABILITY BY MINIMIZING GRAIN LOSS AND MAINTAINING QUALITY THROUGH CORRECT PROCEDURES DURING HARVESTING AND POST-HARVEST OPERATIONS... hard to harvest lodged rice This is the major disadvantage of the reaper - High losses during harvesting and piling over-matured rice - Grain quality is not as good as in the case of manual harvesting if field drying is applied - Higher capital cost - More straw left behind in the field - The mobility of the machine in the field depends on the weight of machine and the size of field - High capacity, less... control in the field and during post-harvest processes in the Mekong Delta of Vietnam Appendix 9 Assessment of Physical and Financial Benefits of CARD 026/VIE-05 project April 2010 208 Appendix 9 Assessment of Physical and Financial Benefits of CARD 026/VIE-05 project To achieve the physical and ultimately financial benefits to the farmers by the way of controlling rice cracking we propose that the measures... grain and rice cracking due to over drying or rewetting of the grain, if the rice is not threshed in time The major disadvantages of this method are: Rewetting from straw or soil which can cause rice cracking and high proportion of broken rice during milling Rewetting during night time due to high humidity resulting in grain cracking and low milling yield Non-uniform drying due to uneven spreading of. .. reduction in the grain losses during harvesting • Machine harvesting is beneficial in terms of quick harvesting of the crop and hence in terms of minimizing harvesting losses 193 Grain cracking and head rice yield (HRY) Effect of harvesting method Harvesting method as such may not affect grain cracking and head rice recovery (Check), but manual harvesting often results in delayed harvesting, and this... harvesting: - High capacity + Harvesting by combineharvester (axial flow threshing) - Only one operator and one worker are required for running the machine - The mobility of the machine in the field depends on the weight of machine and the size of field - Hard to harvest lodged rice 192 - Grain quality good - The machine consists of many parts and elements which lead to complex operation and maintenance -. .. 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 collected in two provinces in Mekong Delta at the same time when experiments were conducted are presented in Table 9 The results indicate that the grain cracking is not significantly affected by the method of threshing... surface of grain Drying methods After harvesting (cutting in the field) the rice lots are dried by different methods: 196 1 Field drying 2 Sun drying 3 Artificial drying Field drying Field drying is practiced prior to threshing when hand or reaper is used for cutting the rice The drying rate will highly dependent on the weather condition and the stage of harvesting There are losses due to shattering of the. .. quality of rice The head rice means the whole grain unbroken rice which has at least 75% of the original length of the brown rice In an ideal condition the head rice recovery is expected to be above 59% Rice cracking occurred prior to milling due to improper harvesting and subsequent drying practices, presence of immature grain, chalkiness in the grain and milling conditions are the main contributors of. .. investment Harvesting by reaper, combinecollection and threshing - The reaper machine is not heavy, high capacity ( 1-6 ha/day); it can work in the soft soil field - The combine- collecting and threshing machine can work in soft soil field where heavy combine harvester could not work - High amount of rice stem ( 2-3 times compared to manual harvesting) increased time and energy for piling and threshing; it’s . completion of the threshing operation. Losses during crop and grain handling: • Handling loss: mature grain lost during lifting, hauling, stacking, pouring, and bagging of crop and grains. Incorrect. dependent on the weather condition and the stage of harvesting. There are losses due to shattering of the grain and rice cracking due to over drying or rewetting of the grain, if the rice is not. operator and one worker are required for running the machine. - The mobility of the machine in the field depends on the weight of machine and the size of field. - Hard to harvest lodged rice.