Nitrogen fertiliser requirements for representative soils of the - PowerPoint PPT Presentation

Nitrogen fertiliser requirements for representative soils of the Lower Burdekin cane growing district Julian Connellan 1 , Phil Moody 2 1 Sugar Research Australia, Burdekin 2 Queensland DSITI, Dutton Park 13 th October 2015 David Defranciscis (Chairman) Steering committee

Background  October 2009 the Great Barrier Reef Protection Amendment Act was introduced requiring growers to follow a regulated method for determining N application rates.  In response to industry concern DEHP funded a number of trials across the Burdekin.  The trials began in 2011  Aim is to assess the suitability of nitrogen application rates in the Burdekin, giving consideration to profitability, sustainable production and the potential for impacts on the environment.

Current status  To date established 23 replicated block trials in the Delta and BRIA cane growing areas  10 established in 2011, 4 established in 2012, 1 in 2013, 4 established in 2014 and 4 established in 2015  Active sites include: • four plant • four 1 st ratoon • one 2 nd ratoon • three 3 rd ratoon • possibly two 4 th ratoon  Sites range in size from 4 to 10 hectares

Trial design Three to four treatments • Treatment 1 – low rate (P130 kg N/ha, R170 kg N/ha) • Treatment 2 – rate determined by the Regulated Method/Six Easy Steps (P170 kg N/ha, R210 kg N/ha) • Treatment 3 – traditional grower rate (P210 kg N/ha, R250 kg N/ha) • Treatment 4 – a high rate (P250 kg N/ha, R290 kg N/ha)  Three to four replications at each site  Six Easy Steps rate based on DYP of 180 t cane/ha and discount for soil mineralisation potential

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2014 Harvest results Mean cane yield (tc/ha) for each nitrogen rate treatment at six 2 nd ratoon trial sites Treatments Grower ID 170 kg N/ha 210 kg N/ha 250 kg N/ha 290 kg N/ha 2 107.5 105.8 106.2 6 107.7 b 111.4 ab 115.7 a 117.2 a 7 128.2 124.6 124.5 125.5 8 79.1 b 81.6 b 81.5 b 85.6 a Sites with P<0.05 are highlighted Means followed by a common letter are not significantly different at the 5% level *Indicates elevated levels of nitrates in irrigation water (>2 mg/L of NO 3 -N) Mean sugar yields (ts/ha) for each nitrogen rate treatment at six 2 nd ratoon trial sites Treatments Grower ID 170 kg N/ha 210 kg N/ha 250 kg N/ha 290 kg N/ha 2 16.3 16 15.9 6 18.8 19.2 19.1 19.4 7 20 19.4 19.2 19.2 8 13.7 14 14 14.4

Mean cane yield (tc/ha) for each nitrogen rate treatment for a plant crop Treatments Grower ID 150 kg N/ha 190 kg N/ha 230 kg N/ha 15 196.6 201.4 198.5 Mean sugar yields (ts/ha) for each nitrogen rate treatment for a plant crop Treatments Grower ID 150 kg N/ha 190 kg N/ha 230 kg N/ha 15 26.2 25.7 25.5 Note. Moddus was applied to this trial site

Apparent nitrogen fertiliser use efficiency (aNUE) - k g of N applied to produce 1 tonne of sugarcane kg of applied N to produce 1 tonne of sugarcane for 4 plant crops Applied N Yield (tc/ha) kg of N applied to produce Grower ID (kg/ha) 1 tonne of sugarcane 2 170 141 1.2 6 170 111 1.5 8 170 131 1.3 15 150 197 0.8

Apparent nitrogen fertiliser use efficiency (aNUE) - k g of N applied to produce 1 tonne of sugarcane kg of applied N to produce 1 tonne of sugarcane for 4 plant crops Applied N Yield (tc/ha) kg of N applied to produce Grower ID (kg/ha) 1 tonne of sugarcane 2 170 141 1.2 6 170 111 1.5 8 170 131 1.3 15 150 197 0.8

Improving our understanding of where the applied N is going  Can use a simplistic method of looking at kg of N applied to produce 1 tonne of sugarcane as shown in the previous slide however this is only part of the story • It does not explain: • Where has the N has gone • How much N the plant used • How much N is left in the soil after the crop is harvested  To develop a better understanding of where the N is going a partial nitrogen budget can be used

Partial Nitrogen Budget B C Fertiliser Denitrification Above ground Amendment Biomass uptake inputs C oxidation Mineralisation E A Final soil Initial soil pools pools Runoff, sediment Leaching D Below ground biomass uptake Nutrient inputs, outputs and status components of a partial nitrogen budget

Initial soil pools (A) • Prior to planting all trial sites soil sampled – Soil cores down to 1m in 20cm increments – Soil samples tested for mineral N (Nitrate N +Ammonium N) • Kg/ha of mineral N in the top 60cm of the soil profile calculated – Generally mineral N levels vary widely from site to site (15 kg N/ha – 114 kg N/ha)

Fertiliser amendment inputs (B) • Fertiliser applied using purpose build fertiliser box with load cell technology – Recommend N application rate for plant crop according to regulated method (Six Easy Steps) is generally around 150-170 kg N/ha

Above ground biomass uptake (C) • Conducted at harvest • Stalks are sampled and broken down to components such as millable stalk, leaf, cabbage and trash and analysed for N content • Using yield data and the N content of the plant components able to determine the amount of nitrogen captured by the crop Crop N varies widely from site to site (80 – >200kg N/ha)

Below ground biomass uptake (D) • Roots and stool • Below ground biomass N is approximately 30% of the total above ground biomass N • Little knowledge about the dynamics of N accumulation in the below ground biomass 100 kg N/ha A crop with 100kg N/ha in the above ground biomass will have approximately 30kg N/ha in the below ground biomass 30 kg N/ha

Final soil pools (E) • Following harvest soil samples taken from all strips in each trial site • Soil samples taken in 20cm increments (0-20cm, 20- 40cm, 40-60cm, 60-80cm and 80-100cm) down to 1m and analysed for mineral N • Mineral N following harvest was found to be low in all treatments at all sites across the Burdekin. • Often less than 30kg N/ha in the top 60cm of the soil profile

Partial Nitrogen Budget B C Fertiliser Denitrification Above ground Amendment Biomass uptake inputs C oxidation Mineralisation E A Final soil Initial soil pools pools Runoff, sediment Leaching D Below ground biomass uptake Nutrient inputs, outputs and status components of a partial nitrogen budget

Partial Nitrogen Budget B C Fertiliser Denitrification Above ground Amendment Biomass uptake inputs C oxidation Mineralisation E A Final soil Initial soil pools pools Runoff, sediment Leaching D Below ground biomass uptake Nutrient inputs, outputs and status components of a partial nitrogen budget

N Budget N inputs = N outputs Sugar Mill Grower 6. Plant Crop (yield = 111 tc/ha) N Inputs kg of N/ha N Outputs kg of N/ha Crop Biomass Fertiliser 170 118 Soil profile mineral N (above-ground) 26 kg N/ha is unaccounted for 32 (0-60cm) Crop Biomass (below-ground) 35* Irrigation 0 Mineral N remaining in soil post 23 harvest (0-60cm) Soil N mineralisation Unknown Subtotal (A) 202+ Subtotal (B) 176 Sugar Mill Grower 6. Plant Crop (yield = 113 tc/ha) N Inputs kg of N/ha N Outputs kg of N/ha Fertiliser 210 Crop Biomass 120 Soil profile mineral N (above-ground) 27 (0-60cm) Crop Biomass (below-ground) 36* Irrigation 0 Mineral N remaining in soil post 51 kg N/ha is unaccounted for 30 harvest (0-60cm) Soil N mineralisation Unknown Subtotal (A) 237+ Subtotal (B) 186 Note. This budget does not take into account soil N mineralisation * Below ground biomass N is estimated as 30% of above ground biomass N

N Budget N inputs = N outputs Sugar Mill Grower 15. Plant Crop (yield = 197 tc/ha) N Inputs kg of N/ha N Outputs kg of N/ha Crop Biomass Fertiliser 150 196 Soil profile mineral N (above-ground) 112kg N/ha is being supplied 27 (0-60cm) Crop Biomass (below-ground) 59* through soil N mineralisation Irrigation 0 Mineral N remaining in soil post 34 harvest (0-60cm) Soil N mineralisation Unknown Subtotal (A) 177+ Subtotal (B) 289 Sugar Mill Grower 15. Plant Crop (yield = 199 tc/ha) N Inputs kg of N/ha N Outputs kg of N/ha Fertiliser 230 Crop Biomass 233 Soil profile mineral N (above-ground) 27 (0-60cm) Crop Biomass (below-ground) 70* Irrigation 0 Mineral N remaining in soil post 70 kg N/ha is being supplied 24 harvest (0-60cm) Soil N mineralisation Unknown through soil N mineralisation Subtotal (A) 257+ Subtotal (B) 327 Note. This budget does not take into account soil N mineralisation * Below ground biomass N is estimated as 30% of above ground biomass N

Closing comment • N requirement calculated by the Regulated Method/Six Easy Steps was more than enough for maximum cane and sugar yields for most crops harvested in 2014.

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Soil moisture monitoring

2012 Harvest data- Plant crops Mean yield (tc/ha) for each treatment at 10 trial sites Treatments Grower ID 130 kg N/ha 170 kg N/ha 210 kg N/ha 250 kg N/ha 125 a 118 a 128 a 133 a 1 * 2 135 b 141 ab 144 a 153 b 157 ab 163 a 163 a 3 * 4 * 143 a 145 a 139 a 144 a 6 106 a 111 a 113 a 113 a 7 * 150 a 152 a no data 151 a 8 126 b 131 ab 134 a 136 a 9 90 a 96 a 95 a 96 a 10 122 b 129 a 130 a 133 a 11 127 c 137 b 142 a Mean yield (tc/ha) 128 132 132 134 Sites with P<0.05 are highlighted Means followed by a common letter are not significantly different at the 5% level * Indicates elevated levels of nitrates in irrigation water (>3 mg/L of NO 3 -N )