The impact of residue on air temperature in the canopy phenology biomass and grain yield of chickpea

Author: Andrew Verrell (NSW Department of Primary Industries, Tamworth), Leigh Jenkins (NSW Department of Primary Industries, Trangie) and Matthew Grinter (NSW Department of Primary Industries, Tamworth) | Date: 27 Feb 2017

Take home messages

  • Residue spread across the soil surface leads to an increase in the incidence of radiant frosts in crop
  • Frost incidence increases with increasing residue loading
  • Frost risk is reduced by sowing chickpea between standing wheat rows which is as good as sowing into bare soil
  • High residue loads can change the thermal profile of the crop and lead to delays in the onset of flowering, podding and maturity

Introduction

Chickpea productivity in the northern grains region (NGR) is constrained by several abiotic stresses (Whish et al. 2007) and temperature is one of the most important determinants of crop growth over a range of environments (Summerfield et al. 1990) and may limit chickpea yield (Basu et al. 2009).

The potential evaporative demand for water usually exceeds the water available to the crop representing the greatest limitation to crop production in the NGR. Low-disturbance direct seeding into standing or flattened cereal stubble is the most effective practice to reduce the impact of water stress on chickpea crops. However, surface residues can cause an increase in radiant frost risk and may also affect the micro-climate of the crop canopy impacting on floral initiation, pod set and seed development.

The impact of surface residue on air temperature in the canopy, phenology, biomass and grain yield of chickpea was explored in a series of experiments across the NGR in 2016.

Stubble effects on soil and air temperature

During the day the stubble reflects radiation due to its 'albedo'. A bare, darker soil absorbs more solar radiation than a stubble-covered soil and warms up more readily. The stubble also acts as insulation as it contains a lot of air which is a poor conductor of heat. Finally, the stubble affects the moisture content of the soil. It takes more heat to warm up moist, stubble covered soil than dry, bare soil.

This causes soil temperature of a bare soil to be higher than stubble covered soil during the day (especially in the afternoon). At night, however, the bare soil loses more heat than stubble covered soil due to the lack of insulation (the air-filled stubble being a poorer heat conductor). This is especially noticeable when skies are clear. The air above the bare soil is therefore warmer during the night than the stubble covered soil, while the soil temperature differences become negligible. Therefore stubble cover may lead to a higher incidence of frost than bare soil.

Methods

A replicated split-plot experiment was designed with 3 x varieties; PBA HatTrick, Kyabra and PBA Seamer, as main-plots and 4 x wheat stubble treatments; bare soil, flattened stubble-high load, flattened stubble-low load and standing stubble, as split-plots. Experiments were located at Rowena, Tamworth and Trangie to explore environmental impacts. At the Trangie site the standing stubble treatment was replaced by flattened sorghum stubble – high load.

Experiments were sown between standing wheat rows at Rowena and Tamworth and into cultivated country at Trangie. Stubble treatments were then invoked post sow and prior to crop emergence. At Rowena and Tamworth, the bare soil treatments had all the standing stubble and surface residue removed by hand. The flattened stubble-low load treatments had the existing standing stubble cut at ground level and evenly distributed across the plots. The flattened stubble-high load treatments were established the same way as the low load treatments with the addition of 5 tonne/ha of wheat stubble spread across the plot. The standing stubble treatments remained untouched. At Trangie, the bare soil treatments had any surface residue removed by hand. The standing stubble treatment was replaced by sorghum stubble at a high rate and flattened stubble treatments had supplementary stubble applied to each plot.

Tinytag temperature sensors were placed in the PBA HatTrick plots after crop emergence at two heights within the central plant row; at ground level (0cm) and 50cm. These sensors were set to record temperature at 15 minute intervals. Another Tinytag sensor was place outside the crop area at 150cm above the ground to record ambient temperature at similar time intervals.

Plant establishment counts were taken across all treatments at each site and there were no effects of stubble treatment on plant density. Detailed phenology was recorded at Tamworth and Trangie on a daily basis. At physiological maturity whole plant samples were taken for detailed plant components analysis and whole plots were harvested for grain yield and botrytis grey mould foliar diseases.

Results

1.       Rainfall

The 2016 season was very wet with above average rainfall across the NGR. Rainfall for 2016 was in the highest 10% of historical observations for most of New South Wales inland of the Great Dividing Range (BOM 2016). Growing season (GS) and long term average (LTA) rainfall for the sites were; Tamworth GS = 585mm (LTA = 298mm), Trangie GS = 386mm (LTA = 186mm) and Rowena GS = 457mm (LTA = 210mm). A high intensity foliar fungicide program was implemented at all sites to manage ascochyta blight.

2.       Temperature

It was the sixth-warmest year for New South Wales with maximum temperatures +0.91oC warmer and minimums +1.24oC warmer than the LTA (BOM 2016). These published reviews are state wide and a closer examination of the growing season trends in max and min temperature are warranted.

Figure 1 compares the maximum and minimum monthly average temperatures for 2016 to the maximum and minimum monthly LTA temperatures for the Tamworth site. The Rowena and Trangie sites showed similar trends.

Figure 1. The maximum and minimum monthly average temperatures for 2016 compared to the maximum and minimum monthly long term average temperatures for the Tamworth site.

Figure 1. The maximum and minimum monthly average temperatures for 2016 compared to the maximum and minimum monthly long term average temperatures for the Tamworth site.

In the first five months of the year the max and min temperatures were well above the LTA which was also a very dry period. However, during the GS, the mean monthly max temperature was equal to the LTA during May-July then significantly cooler from August-November during the flowering and grain fill period by -1.08oC compared to the LTA. The average monthly minimum from May-September was warmer by +1.24oC during the vegetative period but cooler during October-November during grain fill by -2.8oC compared to the LTA.

While this data gives us a better understanding of what actually happened at individual sites within the GS it is after all data obtained from a standard weather station which is located 150cm above the ground. Research has found that the difference between air temperature (AT) in the canopy and that recorded at the weather station can be as much as 5oC or greater (Rebbeck and Hayman 2009).

2.1          High temperatures

Comparative data for temperature probes located within the chickpea crop at 0cm and 50cm and screen data at 150cm above ground level are presented in table 1.

High temperatures can impact on yield and Devasirvatham et al. (2012) found that temperatures above 30oC are detrimental to flowering and pod development. Table 1 shows the number of days where AT in crop (0cm and 50cm) exceeded 35oC compared to screen occurrences.

At ground level (0cm) most treatments had much lower numbers of high temperature days compared to the screen which is mainly attributable to canopy shading. What is notable is that the flat high stubble load treatment had substantially higher numbers of hot days compared to the other treatments. This may be due to the high degree of reflected radiant energy from the stubble back into the crop canopy due to its high ‘albedo’.

Table 1. Number of days where temperatures exceeded 35oC, number of frosts (<0oC) and absolute minimum temperature for the stubble treatments at 0cm and 50cm and screen data at 150cm for Trangie, Tamworth and Rowena

Number of days > 35oC

Number of frosts (days)

Absolute min. (oC)

Height

Treatment

Trangie

Tamworth

Rowena

Trangie

Tamworth

Rowena

Trangie

Tamworth

Rowena

0cm

Bare

8

17

5

11

23

4

-3.0

-2.4

-4.3

Flat-High

17

26

20

32

28

23

-5.2

-3.4

-5.0

Flat-Low

10

18


15

23


-3.8

-2.5

Standing

14

9

13

7

-1.6

-4.3

Sorghum-flat

10


24


-4.3

50cm

Bare

16

21

11

24

19

17

-3.7

-2.4

-4.0

Flat-High

26

22

21

24

20

18

-4.1

-2.7

-4.3

Flat-Low

22

22


23

19


-3.8

-2.4

Standing

19

18

17

18

-2.8

-4.0

Sorghum-flat

23


29


-4.2

150cm

Screen

24

27

12

8

5

7

-2.0

-0.9

-1.8

At 50cm above the ground the number of days >35oC were comparable to the screen occurrence. It took some months for the crops to attain and then exceed 50cm in height. The lower incidence of extreme hot days at Rowena reflects the fact that this crop was the first to mature and was harvested by the 24th of November compared to 14th of December and 20th December for Tamworth and Trangie, respectively.

2.2          Frosts

The biggest difference in screen data versus AT in the crop canopy is for the number of frost events where temperatures were below 0oC. The screen data suggests that there were 8, 5 and 7 frost events at Trangie, Tamworth and Rowena, respectively. As you can see from the data the number of recorded frost events at ground level and even at 50cm in crop is substantially higher than in the screen.

Again, at ground level a high load of stubble flat on the ground leads to substantially more frost events compared to bare soil and even standing stubble.  Averaged across treatments there were 21, 22 and 11 frosts at Trangie, Tamworth and Rowena, respectively.  In the upper canopy frost events are similar across stubble treatments but still substantially more than in the screen at 150cm above ground level with 25, 19 and 18 frosts at Trangie, Tamworth and Rowena, respectively.

Stubble treatments had their main impact on frosting at ground level with high stubble loads recording colder AT by 1.0oC on average compared to other stubble treatments. AT in the upper canopy were similar across stubble treatments. Absolute minimum canopy AT’s were much lower than screen temperatures both at ground level and in the upper canopy. Compared to the screen it was 2.0-3.0oC colder on average in the canopy across all three sites.

The last recorded screen frosts were; 27th August, 26th August and 28th August, with minimums of -0.13, -0.21 and -1.58oC for Rowena, Tamworth and Trangie, respectively. However, the last in-crop frosts were recorded on; 12th October, 23rd October and 1st November, with minimums of -0.58, -0.82 and -0.37oC for Rowena, Tamworth and Trangie, respectively. These in-crop frosts all occurred in the upper canopy (50cm) of the flat high load stubble treatments across all three sites with no frosting in the other treatments.

3.       Phenology

Temperature is critical to the growth and development of chickpeas and operates at two levels. Firstly, days from sowing to flowering is determined by accumulated thermal units. Secondly, there are cardinal temperatures for biological processes in plants which include a base temperature (Tb), which corresponds with rate = 0, the lower (To1) and upper (To2) thermal boundaries for maximum rates, and a ceiling temperature (Tc), which also corresponds with rate = 0 (Sadras and Dreccer 2015).

In chickpeas cardinal temperatures for node production are Tb = 6.0oC, a single To =22oC, and Tc=31oC (Soltani and Sinclair 2011). Where average mean daily temperatures are lower than 15oC, pollen viability is reduced and flowers will fail to develop into pods.  Table 2 shows the effect of stubble treatments on chickpea phenology at Tamworth. 

Table 2. Average phenology dates for selected characteristics for PBA HatTrick at Tamworth

Treatment

1st flower

50% flower

1st pod

Flowering-cessation

Phys-mat

Bare

2-Sep

20-Sep

13-Oct

3-Nov

18-Nov

Flat-High

7-Sep

23-Sep

14-Oct

5-Nov

22-Nov

Flat-low

9-Sep

24-Sep

14-Oct

3-Nov

22-Nov

Standing

6-Sep

21-Sep

15-Oct

3-Nov

18-Nov

Stubble treatments had a significant effect on the phenology of the chickpea crop. The bare soil treatments commenced flowering earlier and attained each phenology stage earlier than where stubble was present. Compared to the bare soil treatment, the high stubble load treatment had a 5 day delay in the commencement of flowering and a 4 day delay in reaching physiological maturity. However, all stubble treatments had near equivalent total lengths from 1st flower to physiological. maturity; 77, 76, 74, 73 days for the bare, flat-high, flat-low and standing stubble treatments, respectively.

4.       Crop production

Dry matter, grain yield and harvest index (HI) for the three experimental sites are shown in table 3. Across all three sites the flattened high stubble load treatment had the lowest total dry matter while at the northern sites (Rowena and Tamworth) the bare soil and standing stubble treatments had the highest dry matter production. At Trangie, on a hard setting red chromosol, the low stubble load produced the highest dry matter.

At Rowena and Tamworth the bare soil and standing stubble treatments produced the highest grain yields while at Trangie a low load of stubble gave the highest grain yield. There was no difference in HI at Trangie across treatments while at Rowena and Tamworth the lower biomass production of the high stubble load treatment led to a higher HI.  

 Table 3. Total dry matter, grain yield and harvest index for stubble treatments at Trangie, Tamworth and Rowena

Treatments

Total Dry Matter
kg/ha

Grain yield
kg/ha

Harvest
Index

Rowena

Bare soil-No stubble

9,458   a

3,068    a

0.33 b

Flat stubble-High load

7,973   c

2,766  bc

0.35 a

Flat stubble-Low load

8,278 bc

2,634    c

0.32 b

Standing stubble

9,125 ab

2,941 ab

0.32 b

Tamworth

Bare soil-No stubble

9,084   a

2,527   a

0.28 ab

Flat stubble-High load

5,615   c

1,653   c

0.29   a

Flat stubble-Low load

7,744   b

2,119   b

0.27  b

Standing stubble

8,312 ab

2,319 ab

0.27  b

Trangie

Bare soil-No stubble

9,981 b

4,038 b

0.41 a

Flat stubble-High load

7,919 c

3,123 c

0.40 a

Flat stubble-Low load

12,445 a

5,040 a

0.41 a

Flat stubble-Sorghum

9,847 b

4,080 b

0.42 a

Values with the same letter within a column are not significantly different

Conclusion

While 2016 has been recorded as the sixth-warmest year on record for NSW, temperature trends showed that the GS (May-November) was mild with max temperatures from August-November being -1.08oC cooler than the LTA and min temperatures from October-November -2.8oC cooler than the LTA. Coupled with above average rainfall it was a year set up for record yields.

Retaining surface residues is an essential component of the NGR dryland cropping system to ensure fallow stored water is captured to reduce the impact of water stress during grain fill in chickpea crops. However, these set of experiments have shown that surface residues cause an increase in radiant frost incidence and have also led to an increase in the number of days where in crop temperatures have exceeded 35oC.

The change to the thermal profile of the crop due to high residue loads led to a delay in the onset of flowering, podding and physiological maturity of the crop. This has then resulted in a reduction in total dry matter with a corresponding reduction in grain yield compared to the bare soil and standing residue treatments.

In all cases sowing chickpeas between standing wheat residue gave equivalent grain yield outcomes to the bare soil treatment.

This remains the preferred strategy to maximise fallow efficiency and grain yield.

Acknowledgements

The research undertaken as part of project DAN00171 is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC, the author would like to thank them for their continued support. Thanks to Michael Nowland, Scott Richards, Liz Jenkins, Joanna Wallace, Judy Duncan and Andrew George (NSW DPI) for their assistance in the experimental program.

References

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Bureau of Meteorology (2016).  Annual climate statement.

Devasirvatham V, Tan DKY, Gaur PM, Raju TN, Trethowan RM (2012) High temperature tolerance in chickpea and its implications for plant improvement. Crop & Pasture Science 63, 419–428. doi:10.1071/CP11218

Rebbeck M, Hayman P (2009). Managing the risk of frost. Frost risk fact sheet. SA Research and Development Institute.

Summerfield RJ, Minchin FR, Roberts EH, Hadley P (1980) The effects of photoperiod and air temperature on growth and yield of chickpea (Cicer arietinum L.). In ‘Proceedings of International Workshop on Chickpea Improvement’. 28 Feb. –2 March 1979, The International Crops Research Institute for the Semi-Arid Tropics, Patancheru, AP, India. (EdsJMGreen, YLNene, JB Smithson) pp. 121 –149. (ICRISAT Publishing: Hyderabad, India)

Sadras V, and Fernanda Dreccer M (2015) Adaptation of wheat, barley, canola, field pea and chickpea to the thermal environments of Australia. Crop & Pasture Science, 66, 1137–1150 Viewpoint http://dx.doi.org/10.1071/CP15129

Whish JPM, Castor P, Carberry PS (2007) Managing production constraints to the reliability of chickpea (Cicer arietinum L.) within marginal areas of the northern grains region of Australia. AJAR, 2007, 58, 396-405.

Contact details

Dr Andrew Verrell
NSW Department Primary Industries
Ph: 0429 422 150
Email: andrew.verrell@dpi.nsw.gov.au

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