Soil Moisture Probe Newsletter: October 2015

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1 Soil Moisture Probe Newsletter: October 2015 Southern Farming Systems aims to improve nitrogen use efficiency (NUE) of growers in the high rainfall zones of Victoria and Tasmania. SFS has installed 62 soil probes located across the high rainfall zones of Victoria and Tasmania, which record temperature and moisture in 10 cm increments, to a meter below the soil surface, every 15 minutes. Graphs of this data are available on the SFS website, allowing farmers to monitor their local soils, and make informed management decisions, particularly fertiliser applications. Recent Observations The 2015 season began well, with early rains ensuring most crops were sown in favourable conditions, encouraging robust germination and early tillering, while lower rainfall through winter avoided waterlogging and enabled crops to develop extensive root systems. The soil moisture status for most sites at the end of September was higher than at the same time in growing season rainfall was at a Decile 2-3 in the Western Districts. The forecast El Nino didn t negatively impact the crops until October, which was incredibly dry, resulting in a Decile 1 for all areas except for Gippsland. The other major factor was the temperature which was approximately 5 C warmer for the month compared to the long term average. During October, BOM weather stations recorded 4 of normal rainfall at Ballarat and Geelong, and 6 of normal rainfall at Hamilton. Low rainfall was exacerbated by hot and windy conditions, with temperatures above 25 C occurring 11 times at Hamilton and 13 times at Westmere and Sheoaks (near Lethbridge) during the month. These conditions were a result of two factors; a positive Indian Ocean Dipole (IOD) which causes the ocean above Australia to cool, reducing cloud formation and subsequent rainfall, and a negative Southern Oscillation Index (SOI), which causes stable, high pressure systems which also reduce rainfall in the southern region. For many growers in the Western Districts, crops which were sown early in the season, and had finished the majority of flowering before October s hot weather are expected to offer the best yields, while later sown crops and long season winter wheats will require additional moisture as rainfall or stored soil moisture to fill grain. As stored soil moisture has been used extensively during October, and the outlook for November includes low rainfall forecasts, this extra moisture may not eventuate. East Gippsland in contrast received fewer hot days, and significantly higher October rainfall, which has increased stored soil moisture and improved outlooks for a good finish to the season. Table 1a. Soil moisture levels (30 cm to 1 m) at selected Western District probe sites, as a percentage of total subsoil moisture available on October 29 th 2014 and October 29 th Inverleigh Winchelsea Rokewood Werneth Lethbridge Lismore Ballan 1 Skipton Crop Barley Faba beans Canola Canola - Canola Canola Barley Glenthompson Narrapumelap Yatchaw Lake Bolac 1 Lake Bolac Crop Wheat Canola Canola N/A Wheat

2 Moisture Percentage ( cm) Moisture Percentage (30 cm-100cm) Mininera Westmere 1 Tatyoon 1 Tatyoon 2 Duverney Crop Lupins Wheat Barley - Canola Lismore Werneth Winchelsea Inverleigh 1 Rokewood Ballan 1 Skipton Lethbridge Soil Probe Sites (from Table 1a) Soil Probe Sites (from Table 1a) Figures 1a. Soil moisture levels (30 cm to 1 m) at selected soil probe sites, as a percentage of total subsoil moisture available on October 29 th 2014 and October 29 th 2015.

3 Moisture Percentage ( cm) Table 1b. Soil moisture levels (30 cm to 1 m) at Gippsland probe sites, as a percentage of total subsoil moisture available on October 29 th 2014 and October 29 th Date Bairnsdale Rosedale Lindenow Dutson Downs crop Canola Canola Wheat Wheat Bairnsdale Rosedale Lindenow Dutson Downs Soil Probe Sites (from Table 1b) Figure 1b. Soil moisture levels (30 cm to 1 m) at selected soil probe sites, as a percentage of total subsoil moisture available on October 29 th 2014 and October 29 th For an in depth summary of the soil probe activity at six selected sites, read on. The graphs below are generated from 6 trial paddocks (Bairnsdale, Yatchaw (Hamilton), Westmere, Werneth, Winchelsea and Inverleigh) which host soil probes. Reading the summed graphs: the information recorded by the soil probe is used to generate a graph which shows the total amount of soil moisture from 30 cm to 100 cm in the soil profile. This total moisture level is shown by the red or green line, and records moisture continuously from installation until the present month, while the blue bars at the top of the graph show the rainfall that occurred during this period. The graphs below show a selected time period based on the 2015 season. Reading the stacked graphs: the moisture information from the probe is used to generate a graph which shows the moisture level at each 10 cm increment. The top purple line represents the 10 cm moisture probe, if present, or more commonly the black 30 cm moisture probe, while the bottom red line represents the moisture recorded at 1 m in depth. The upper limit of water holding capacity is termed field capacity while the lower limit is termed the wilting point. These levels are shown by the driest to date, and the wettest to date points reached on the soil moisture graphs.

4 Bairnsdale Focus Paddock Bairnsdale summed moisture graph At the Bairnsdale focus paddock the summed moisture level as recorded by the probe from November 1 st 2014 to October 31 st 2015 is displayed below in Figure 2a. This probe site received 67 mm of rain in January and 146 mm in April, which are shown on the graph below as two significant increases in soil moisture (red circles). Moisture levels remained high due to consistent rainfall, until September, when the site received approximately half of the usual monthly total. Added to this, the October rainfall was also low, resulting in a significant soil moisture decline, only alleviated on the 22nd of October by 41 mm of rainfall, increasing the level of soil moisture to 38 total moisture. Figure 2a. Summed moisture data recorded at the Bairnsdale focus paddock from to

5 Bairnsdale stacked moisture graph The graph below shows soil moisture recorded by the Bairnsdale soil moisture probe at 10 cm increments down the profile to 1 metre. During September, soil moisture use occurred to 50 cm in depth (red circle). Depths below this level were unaffected, as the moisture lines are stable throughout the month. However, moisture levels below 50 cm became severely affected between the 3 rd of October and the 17 th of October, with all depths showing declines due to crop water use. This use followed a step wise progression with shallower depths depleted first, then followed by lower levels. This decline was only halted by the rainfall on the 22 nd, which significantly increased moisture levels at 10, 30, 90 and 100 cm levels (blue circles). This increase has been followed by crop water use at 10 cm and 30 cm, reducing soil moisture at these levels. 10 cm 30 cm 100 cm Figure 2b. Stacked moisture data recorded at the Bairnsdale focus paddock from to

6 Yatchaw Focus Paddock Yatchaw summed moisture graph At the Yatchaw focus paddock the summed moisture level as recorded by the probe from October 1 st 2014 to October 31 st 2015 is displayed below in Figure 3a. Moisture level at the start of the season was approximately 50 with rainfall in June and July of 70mm and 75mm increasing stored soil moisture levels to almost 100. Crop water use did not begin until mid-august, with moisture levels declining severely after this, with no alleviation due to low rainfalls of 13mm in September and 4 mm in October. These amounts were used almost instantly by the crop, and consequently the crop has relied almost totally on stored soil moisture, with levels at the end of October being significantly less than at the same time in 2014 (red circles). Figure 3a. Summed moisture data recorded at the Yatchaw focus paddock from to

7 Yatchaw stacked moisture graph The graph below shows soil moisture recorded by the Yatchaw soil moisture probe at 10 cm increments from 30cm to 1 metre in depth. During September, crop water use began at the 30 cm and 40 cm levels, although it was not severe until the beginning of October. Moisture use above 50 cm plateaued by the 15 th of October (red circle), indicating these levels were drained of plant available water. Moisture use below 50 cm then began in earnest in the expected step wise fashion, (red circle), with all levels declining sharply with no alleviation to the end of October. 30 cm 100 cm Figure 3b. Stacked moisture data recorded at the Yatchaw focus paddock from to

8 Westmere Focus Paddock Westmere summed moisture graph At the Westmere focus paddock the summed moisture level as recorded by the probe from October 1 st 2014 to October 30 th 2015 is displayed below in Figure 4a. A dry spring in 2014 caused an enormous decline in soil moisture throughout October and November, which was then relieved by summer rainfall. During the 2015 growing season, consistent rainfall, particularly during June and July (42mm and 45mm), improved soil moisture levels, which then began to decline in early August. This decline has been steady throughout September and October, with no relieve by rainfall. However, moisture levels at this site are actually higher at the end of October 2015 than at the same time in 2014, at 1 and 14 respectively (see red circles). Figure 4a. Summed moisture data recorded at the Westmere focus paddock from to Westmere stacked moisture graph This graph is being updated, and will be available in 2016.

9 Werneth Focus Paddock Werneth summed moisture graph At the Werneth focus paddock the summed moisture level as recorded by the probe from October 1 st 2014 to October 30 th 2015 is displayed below in Figure 5a. At the start of the growing season, moisture levels were approximately 70, peaking in May at the wettest to date since probe installation (100). After this point, soil moisture declined, but remained relatively high until mid-september, when crop water use and low rainfall combined to decrease soil moisture. However, although moisture levels during October 2014 can be seen to be higher than in October 2015, at the end of the month, the moisture levels are identical at 49 (see red circles). Figure 5a. Summed moisture data recorded at the Werneth focus paddock from to

10 Werneth stacked moisture graph The graph below shows soil moisture recorded by the Werneth soil moisture probe at 10 cm increments from 30 cm to 1 metre in depth. During September, moisture levels at all depths remained relatively stable, with the onset of October causing the first signs of crop water use below 30 cm (red circle). This crop water use appears to have started later than other probe sites, with water use at 80 cm and below occurring after the 20 th of October (red circle). 30 cm 100 cm Figure 5b. Stacked moisture data recorded at the Werneth focus paddock from to

11 Winchelsea Focus Paddock Winchelsea summed moisture graph At the Winchelsea focus paddock the summed moisture level as recorded by the probe from October 1 st 2014 to October 30 th 2015 is displayed below in Figure 6a. After an extremely dry finish to 2014, soil moisture levels were restored by rainfall in January of 40 mm. Further rainfall in May of 60 mm further improved stored soil moisture levels, until October, when moisture levels began to decline. The decline at this site is shallower and occurs later than at other sites due to the 2015 crop being faba beans. Moisture levels at the end of October 2014 and October 2015 can be compared using the red circles. Figure 6a. Summed moisture data recorded at the Winchelsea focus paddock from to

12 Winchelsea stacked moisture graph The graph below shows soil moisture recorded by the Winchelsea soil moisture probe at 10 cm increments from 30 cm to 1 metre in depth during September and August As noted above, moisture use has occurred less than at other probe sites, with declines only starting after the 1 st of October. In addition, the 60 cm depth rose in moisture until the second week of October, where it was seen to have been depleted. However, depths below 70 cm have been completely unaffected by crop water use, and have actually risen in moisture throughout September and October. This can be attributed to crop type, as faba beans and other legumes have a lower water requirement than cereals, and will also mature and senesce earlier in hot weather, allowing store soil moisture to recharge without crop water use. 30 cm 100 cm Figure 6b. Stacked moisture data recorded at the Winchelsea focus paddock from to

13 Inverleigh 1 Focus Paddock Inverleigh summed moisture graph At the Inverleigh focus paddock the summed moisture level as recorded by the probe from October 1 st 2014 to October 30 th 2015 is displayed below in Figure 7a. At Inverleigh, crop water use during the decile 1 spring was similar to Winchelsea, with the soil moisture profile also reaching a low of 2 during November. However, soil moisture recharge occurred earlier than at Winchelsea, with moisture levels reaching 100, or wettest to date in January 2015 (see blue circle). Although this moisture peak did decline through the season, rainfall kept soil moisture at about 80 until crop water use began in September. Water use has been consistent with 2014, leaving the profile at 15 on October 30 th 2014 and October 30 th 2015 (red circles). Figure 7a. Summed moisture data recorded at the Inverleigh focus paddock from to

14 Inverleigh stacked moisture graph The graph below shows soil moisture recorded by the Inverleigh soil moisture probe at 10 cm increments from 10 cm to 1 metre in depth during September and October 2015 (excluding 20 cm). Soil moisture at 30 cm declined gradually throughout September, while moisture levels to 70 cm showed small declines on the 14 th of September. More substantial crop water use occurred for these depths occurred after the 28 th September. Depths below 70 cm only began to decline in mid-october, with all levels still declining at the end of October. 30 cm 100 cm Figure 7b. Stacked moisture data recorded at the Inverleigh focus paddock from to