Final report appendix 6
Measurements: Instrumental sphere and calibration
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- Soil moisture, irrigation and temperature monitoring
- Achievements against activities and outputs/milestones
- Key results and discussion
- Instrumental sphere calibration
- Instrumental sphere and variety
- Crop harvest and post-harvest measurements
- Crop verses G force > 50.
- Soil temperature, moisture and tension.
Measurements:Instrumental sphere and calibration.The IS used was designed and manufactured by Sensor Wireless Inc and is known as the Smart Spud™. This IS contains a tri-axial (x, y, z-axis) accelerometer that measures changes in acceleration over time and reports this as peak acceleration in gravitational (G) forces. The information from the Smart Spud™ is recorded via a receiver and sent to a portable computer where the data can be downloaded. G is a measurement of gravitational units where 1 G = 9.81 m/s2. The higher the level of G force measured the higher the severity of the impact. Both round and oblong polyethylene casings can be used with the Smart Spud™ depending on what shape of potato is to be harvested. The Smart Spud™ was calibrated to the bruise type and severity of Atlantic and Granola potatoes grown under WA conditions. Both varieties were dropped from incremental 10 cm heights up to 100 cm using a pendulum device (Mathew and Hyde 1997). There were 10 replicates per drop height and both the bud and stem end were impacted. 48 hours after using the pendulum the potatoes were examined and peeled to determine type of bruise and severity (Henderson and Bennett 1999). The same Smart Spud™ was used with the same round polyethylene casing in this study to keep the results consistent. Soil moisture, irrigation and temperature monitoring:Volumetric soil water (% v/v) was monitored automatically at 3 depths (0-15, 15-30 and 30 cm) and 15 minute intervals using stainless steel volumetric water content probes (Campbell Scientific, SC 625, based on time domain reflectometry (TDR)) inserted at 30 degrees at 0 - 15 and 15 - 30 cm or horizontally at 30 cm in the soil early post planting and prior to crop emergence. Soil temperature was monitored automatically at a depth of 15 cm using a separate temperature probe (109 L) whilst rainfall and irrigation was recorded in 0.2 mm increments using a ‘tipping bucket unit (Ecowatch® 7852). A tensiometer (Irritrol ®) placed at 30 cm soil depth was used to measure soil tension in kPa via a pressure transducer. The tension measured at 30 cm was correlated with volumetric soil moisture measured by the TDR probe inserted at 30 cm horizontally as described above. All the monitoring units were connected to a logger (CR 200) via a cable and data downloaded via a telephone modem (Maxon 5100). Computer software ‘R-Logger’, developed using the freely available ‘R’ program, allowed irrigation timing, depth and soil moisture to be summarized via a graphical interface and emailed as a PDF to participating growers. The unit was powered by a 7.5 Ah, 12 volt sealed lead acid battery recharged by a 10 watt solar panel and all components were housed in a safe case. At the time of harvest the current soil temperature was directly measured using a hand held temperature probe. Data analysisFrom the calibration of the IS and potato varieties grown under WA conditions the G force readings can be grouped into the following thresholds: Low impacts: < 50 G Medium impacts: 50 - 99 G High Impacts: > 100 – 1149 G Very high impacts: 150 – 199 G Extremely high impacts: >200 G Analysis of variance (ANOVA) and non linear regressions were performed on the data to determine whether there was any difference between growers, difference between harvest speeds and growers, relationship between temperature and level of bruising and the relationship between grower harvest speed and level of bruising. Achievements against activities and outputs/milestonesObjective 2: Develop and implement low-cost schemes that significantly improve the access of Indonesian farmers to quality potato seed.
PC = partner country, A = Australia Key results and discussionResultsVarietal differences in response to impactsBlack spot bruise began appearing on the Atlantic seed at a 20 cm drop height and progressively increased until 60% of tubers were damaged at 60 cm (Figure 6.1). After this maximum black spot bruise fell to 0% at 100 cm. Shatter bruise was first seen at a 50 cm drop height and then rapidly increased to 100% at 80 cm. Granola seed did not show any bruising until 60 cm where both black spot and shatter bruise appeared and progressively increased until 100% of the seed were affected at 90 cm drop heights (Figure 6.2). 
Figure 6.1: Black spot and shatter bruise of Atlantic tubers at each drop height. 
Figure 6.2: Black spot and shatter bruise of Granola tubers at each drop height Instrumental sphere calibration
Figure 6.3: The G force readings from the Smart Spud™ with the round casing at each height increment and line of best fit y = 276.62 - 365 exp(-0.053x), R2 = 96. The Smart Spud™ was calibrated at each height and indicated at 10 cm a value of approximately 50 G (Figure 6.3). Initially as drop height increased G force increased rapidly until the 50 cm drop height where any subsequent increase in drop height did not correspond with a large increase in G force. As a result an exponential curve could be fitted to the data to predict the G force for any subsequent drop height. Instrumental sphere and variety
Figure 6.4. Relationship (2 split lines) between tuber impact (G force) and % bruising in Atlantic tubers with a pulp temperature of 15°C. The vertical line intercepts the x axis at the level of impact (212 G) above which significant tuber damage is first observed (threshold). Equations: for line 1; y = 33.1 + 0.22 (x - 212) where x < 212 and for line 2; y = 33.1 + 0.88 (x - 212) where x > 212 (R2= 0.7). 
Figure 6.5. Relationship (2 split lines) between tuber impact (G force) and % bruising in Granola tubers with a pulp temperature of 15°C. The vertical line intercepts the x axis at the level of impact (212 G) above which tuber damage is first observed (threshold). Equations: for line 1; y = 0 where x < 212 and for line 2; y = 1.12 (x - 212) where x > 212 (R2= 0.30). Crop harvest and post-harvest measurementsAtlanticAveraging the combined data for Atlantic shows there were 18 harvest runs and 15 bunker drops per farmer (Table 6.3a). Average time taken for the IS to travel through the harvester was 50 seconds and the average temperature was 11.7 °C. The bruising of the Atlantic tubers can be predicted from these results using the equations shown in Figure 6.4. Predicted percentage of tubers bruised was 4.0% with a range from 1.9 to 6.7%. Table 6.3a. Instrumented sphere harvesting measurements of 5 individual Atlantic crop plus mean values during harvesting. The average acceleration is used to predict the percentage of tubers bruised using the equations shown in Fig 6.4.
GranolaThe Granola data shows of the 22 harvest runs (Table 6.3b) the average time taken for the IS to travel through the harvester was 52 seconds and the temperature was 11.1 °C. The bruising of Granola tubers can be predicted using the equations shown in Figure 6.5. Predicted percentage of tubers bruised was 0%. Table 6.3b. Instrumented sphere harvesting measurements of one Granola crop during harvesting. The average acceleration is used to predict the percentage of tubers bruised using the equations shown in Fig 6.5.
Crop verses G force > 50.The majority of impacts greater than 50 G on the harvesters were 50-99 G or medium range impacts, with Crops 2, 3, 4, 5a, 5b all recording 100% impacts in this range (Figure 6.6, top graph). Crop 6 had impacts on the harvester that were in the 100-149 G, 150-199 G and > 200 G ranges and this lead to the average of all crops being represented in those ranges. The higher impacts detected in crop 6 led to the highest predicted bruise level for Atlantic of 6.7% of tubers bruised (Table 6.3a). Only Crop 3 had 100% of bunker drops in the 50-99 G range whilst Crops 4 and 6 are not represented as there was no bunker on the harvester (Figure 6.6, middle graph). Crop 5b had the highest number of impacts > 200 G for the bunker drop whereas Crop 2 had 35% of impacts in the high impact range (100-149 G). Crop 1 and 5a had impacts in the very high impact range (150-199 G). Crop 5b used the same machinery as crop 5a, the difference was a faster harvester driver. The predicted bruising for these crops was 1.9% and 2.7% respectively showing that a change of operator can increase bruising by 142%. 
Figure 6.6. Percentage of impacts greater than 50 G from the harvester (top graph), from the bunker (middle) and the combined (bottom) for the 6 different crops. Separate colours represent separate growers with Crop 1 = red, Crop 2 = brown, Crop 3 = orange, Crop 4 = yellow, Crop 5a = light green, Crop 5b = turquoise, Crop 6 = dark green, Average = dark blue. There were significant differences between growers and the combined number of impacts greater than 50 G per run for the harvester and bunker drops (P = 0.001) (Figure 6.7). Crop 6 had significantly higher number of impacts > 50g than any other crop with 2.1 impacts, followed by Crops 1 (1.4 impacts) and 2 (1.1 impacts). Crops 3 (0.4 impacts), 4 (0.4 impacts) and 5 (0.8 and 0.7) impacts were not significantly different to one another but were significantly lower than Crops 6, 1 and 2. 
Figure 6.7. The average number of combined impacts >50 G per run for all crops. LSD = 0.53 Bunker versus harvest.There is a significant difference between the number of impact events greater than 50 G at the bunker drop compared with the harvester impacts for all crops (p = 0.039) (Figure 6.8). The bunker to bin drop averaged 1.2 impacts of >50 G every drop whereas the harvester only averaged 0.89 impacts >50 G every run. 
Figure 6.8. Average impacts > 50 G for the bunker to bin drop and the harvest runs for all crops. LSD = 0.31. Soil temperature, moisture and tension.Crop 6 had the highest mean soil temperature of the crops in the study at 21.5 °C and a highest soil temperature of 30.6 °C (Table 6.4). All crops had a mean soil temperature of between 19.2 and 21.5 °C. Crop 2 had the highest soil moisture of 35.2% with a mean of 21.8% and this meant had the highest soil tension at -10.2 kPa. Crop 5 was the driest at only 8.3% soil moisture with the lowest tension at – 37.5 kPa. Table 6.4. The mean, median, minimum and maximum soil temperature, moisture and tension for all 6 crops.
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