IMPROVING FARMER’S PROFITABILITY BY MINIMIZING GRAIN LOSS AND MAINTAINING QUALITY THROUGH CORRECT PROCEDURES DURING HARVESTING AND POST-HARVEST OPERATIONS " potx

Extension Manual MS7 Eng.doc IMPROVING FARMER’S PROFITABILITY BY MINIMIZING GRAIN LOSS AND MAINTAINING QUALITY THROUGH CORRECT PROCEDURES DURING HARVESTING AND POST- HARVEST OPERATIONS EXTENSION WORKERS MANUAL 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. 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. 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. Extension Manual MS7 Eng.doc Types of Losses Harvesting Time At the mature date G After the mature date G+V Extension Manual MS7 Eng.doc 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. Extension Manual MS7 Eng.doc SUMMARY OF POST-HARVEST LOSSES Table 1 is the summary of total post-harvest losses 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 1: 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 two cases of losses that can be highlighted in Table 1. 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. Extension Manual MS7 Eng.doc 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 2 presents the estimated days from sowing to harvest for various varieties in MRD. Table 2. 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. Extension Manual MS7 Eng.doc 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. 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 3: Optimal harvesting time for highest HRY (coloured numbers are the optimal growing time for harvesting) Variety Season Growing time (day) Rainy 88 90 92 94 96 98 OM1490 Dry 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 heat rice yield among several varieties obtained in Mekong Delta during 4 seasons of experiments in 2006-2008. 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) 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 (% ) 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:OM2718 (Rainy season 2006) Variety: OM 1490 (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) Extension Manual MS7 Eng.doc Do Not harvest late after the maturity date in order to avoid cracking and to increase HRY Field experiments indicated that: 4-6 days late harvesting increase cracking by up to 24%, and reduce HRY by up to 28%. Table 4 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 harvetsing). Theses varieties need to be harvested earlier. Table 4: Losses of Head Rice Yield (HRY %) due to late or early harvesting. Variety Season Losses of HRY (%) in comparison to optimal harvesting time Rainy 0 1.57 4.31 10.07 15.79 17.77 OM1490 Dry 1.69 0.97 0 3.33 7.65 11.55 Rainy - - 0 5.15 7.08 3.20 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. Extension Manual MS7 Eng.doc Extension Manual MS7 Eng.doc 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. 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 was harvested later than the optimum harvest time. 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). 2. INFLUENCE OF HARVESTING METHOD ON THE RICE CRACKING AND QUALITY LOSSES Harvesting systems vary from region to region and include different methods for harvesting, hauling, threshing and cleaning. The goal of good harvesting is to ensure maximum grain yield through minimizing grain loss and the prevention of quality deterioration, including cracking. A wide variety of harvesting tools is used, such as knives, sickles, animals, stationary threshing machines, tractor-mounted harvesters, and self-propelled combine harvesters. In Vietnam including Mekong Delta, the most common systems for paddy harvesting are: 1. Manual harvesting, collecting by hand, followed by machine threshing (no more manual threshing in Vietnam) Manual cutting Manual collecting Machine threshing 2. Harvesting by reaper, manual collecting followed by machine threshing Cutting by reaper Manual collecting Machine threshing A lot of labours are required for manual collecting after harvesting by reaper. Extension Manual MS7 Eng.doc [...]... threshing loss of 1.0% for combine harvester was estimated by the manufacturer On an average, mechanical harvesting reduces harvesting losses Table 6: Effect of harvesting methods on the harvesting losses Harvesting method Hand Reaper Hand and heaped immediately Hand and dried in the sun (one day) Reaper and heaped immediately Reaper and dried in the sun (one day) Combined harvester Shattering losses (%) Harvesting. .. method and also due to time of harvesting (particularly late harvesting) is an important factor to consider for 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 Grain cracking and head rice yield (HRY) Effect of harvesting method Harvesting method as such may not affect grain. .. consists of many parts and elements which lead to complex operation and maintenance - Degree of cleanness is not high when grain moisture is high - The mobility is not high where the chain is used The investment cost is high Estimated harvesting losses Harvesting losses consist of shattering and threshing losses Table 6 shows each component and total harvesting losses The total harvesting losses can be as...3 Machine harvesting with a reaper, followed by combined collection-threshing Cutting by reaper Combined collection and threshing Cutting and laying the crop on a windrow is done using a reaper, followed by collection and threshing using a machine 4 Combine harvesting The combine harvester combines all operations: cutting, handling, threshing and cleaning The comparison between the harvesting methods... temperature and moisture differences between the layers of bed Sun drying has some limitations: • Not possible during rain and at night Any delay leads to excess respiration and fungal growth causing losses and yellowing • Labor intensive and has limited capacity • Overheating causes cracking of some grains and result in low milling quality Extension Manual MS7 Eng.doc • Mixing operation is labour intensive and. .. 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 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... grain cracking and head rice recovery, but manual harvesting often results in delayed harvesting, and this can cause grain cracking and reduced head rice recovery Extension Manual MS7 Eng.doc Thus, when harvesting is to conducted to be manually, it is important to time the operation so that crops can be harvested at correct time In addition, manual harvesting results in higher scattering losses in comparison... respiration loss 13% or less Insect damage 9 % or less Loss of viability Delays in drying, incomplete drying or uneven drying will result in qualitative and quantitative losses including: • Yellowing or discoloration caused by mold development and heat build-up from respiration • Development of rice cracks with eventual reduced milling yields caused by high temperatures and re-wetting of grains • Loss of... of germination and vigor caused by grain respiration, mold and insect activities, or from exposure of grains to temperatures above 42ºC • Damage caused by insects that are more active at higher moisture levels Principles of drying Drying of grains involves exposing grains to ambient air with low relative humidity or to heated air or to the sun The moisture evaporates from the grain and then the drying... Harvesting losses (%) 2.6-4.4 1.2 2.4-4.2 1.1 1.8 0.8 1.2-3.0 Threshing losses (%) 1.4 1.5 1.0 2.3-2.5 0.7 1.3-1.5 The information shown above is for the case when crops are harvested at a correct time Due to longer time required for harvesting, it is likely that manual harvesting will result in greater delay in harvesting time, and hence greater harvest losses Thus, • Shattering loss due to harvesting . IMPROVING FARMER’S PROFITABILITY BY MINIMIZING GRAIN LOSS AND MAINTAINING QUALITY THROUGH CORRECT PROCEDURES DURING HARVESTING AND POST- HARVEST OPERATIONS EXTENSION. 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 high. Estimated harvesting losses Harvesting losses consist of shattering and threshing losses. Table 6 shows each component and total harvesting losses. The total harvesting losses can be as