Nitrogen leaching from the root zone of sugarcane and bananas in the humid tropics of Australia

Agriculture, Ecosystems and Environment 180 (2013) 68–78

Contents lists available at ScienceDirect

Agriculture, Ecosystems and Environment journal homepage: www.elsevier.com/locate/agee

Nitrogen leaching from the root zone of sugarcane and bananas in the humid tropics of Australia J.D. Armour a,∗ , P.N. Nelson b , J.W. Daniells c , V. Rasiah d , N.G. Inman-Bamber e a

Department of Natural Resources and Mines, PO Box 156, Mareeba, 4880, Australia School of Earth and Environmental Sciences, James Cook University, Cairns, 4870, Australia Department of Employment, Economic Development and Innovation, PO Box 20, South Johnstone, 4859, Australia d Department of Natural Resources and Mines, PO Box 937, Cairns, 4870, Australia e CSIRO, Private Mail Bag PO, Aitkenvale, 4814, Australia b c

a r t i c l e

i n f o

Article history: Received 25 February 2011 Received in revised form 18 April 2012 Accepted 11 May 2012 Available online 15 June 2012 Key words: Great Barrier Reef Deep drainage Fertiliser management Soil acidification WaterSense

a b s t r a c t Loss of nitrogen in deep drainage from agriculture is an important issue for environmental and economic reasons, but limited field data is available for tropical crops. In this study, nitrogen (N) loads leaving the root zone of two major humid tropical crops in Australia, sugarcane and bananas, were measured. The two field sites, 57 km apart, had a similar soil type (a well drained Dermosol) and rainfall (∼2700 mm year−1 ) but contrasting crops and management. A sugarcane crop in a commercial field received 136–148 kg N ha−1 year−1 applied in one application each year and was monitored for 3 years (first to third ratoon crops). N treatments of 0–600 kg ha−1 year−1 were applied to a plant and following ratoon crop of bananas. N was applied as urea throughout the growing season in irrigation water through mini-sprinklers. Low-suction lysimeters were installed at a depth of 1 m under both crops to monitor loads of N in deep drainage. Drainage at 1 m depth in the sugarcane crops was 22–37% of rainfall. Under bananas, drainage in the row was 65% of rainfall plus irrigation for the plant crop, and 37% for the ratoon. Nitrogen leaching loads were low under sugarcane (<1–9 kg ha−1 year−1 ) possibly reflecting the N fertiliser applications being reasonably matched to crop requirements and at least 26 days between fertiliser application and deep drainage. Under bananas, there were large loads of N in deep drainage when N application rates were in excess of plant demand, even when applied fortnightly. The deep drainage loss of N attributable to N fertiliser, calculated by subtracting the loss from unfertilised plots, was 246 and 641 kg ha−1 over 2 crop cycles, which was equivalent to 37 and 63% of the fertiliser application for treatments receiving 710 and 1065 kg ha−1 , respectively. Those rates of fertiliser application resulted in soil acidification to a depth of 0.6 m by as much as 0.6 of a unit at 0.1–0.2 m depth. The higher leaching losses from bananas indicated that they should be a priority for improved N management. Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved.

1. Introduction As agriculture expands and intensifies across the globe, and particularly in the tropics, it is becoming increasingly important that fertilisers be used efficiently (Drigo, 2005; Wadley et al., 2006). Insufficient or excessive use of fertilisers decreases profitability and can degrade health of the soil and surrounding environment. Excessive use of nitrogen fertilisers can lead to soil acidification (Helyar and Porter, 1989) and loss of nitrate by leaching to groundwater and hence surface water, particularly in humid environments (Aulakh and Malhi, 2005). Fertiliser rate trials are the first step in determining economic optimum application rates. While many fertiliser rate trials have been carried out, they continue to be necessary as

∗ Corresponding author. Tel.: +61 7 40484705; fax: +61 7 40922366. E-mail address: [email protected] (J.D. Armour).

combinations of crop type and environment evolve. However, from an environmental perspective, even more important is quantification of nutrient losses. For nitrogen fertilisers in humid environments, the main loss pathway is nitrate in deep drainage (e.g. Banabas et al., 2008; Moody et al., 1996). However, there is limited information on leaching loss of nitrogen under different cropping practices in the humid tropics, particularly over multiple years. In the humid tropics of northeast Australia, agriculture is the dominant land use on non-mountainous areas, and loss of nutrients is of particular concern as these areas drain into the aquatic and marine ecosystem of the World Heritage-listed Great Barrier Reef and its catchments (Brodie et al., 2008). Sugarcane (193,600 ha) and bananas (11,100 ha) are the major intensive crops in the Wet Tropics Bioregion, which has an average annual rainfall of 1850 mm (McDonald and Weston, 2004). Both crops are reliant on fertiliser N with current mean annual rates of 138 kg ha−1 for sugarcane

0167-8809/$ – see front matter. Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.agee.2012.05.007

J.D. Armour et al. / Agriculture, Ecosystems and Environment 180 (2013) 68–78

69

Table 1 Some soil properties for the sugarcane and banana sites. Depth (m)

pH (1:5 water, 4A1)a

OC (%, 6A1)a

ECEC (cmolc kg−1 , 15J1)a

Sugarcane 0–0.1 0.1–0.2 0.2–0.3 0.3–0.6

5.5 5.5 5.8 5.2

0.9 0.7 0.4 0.3

2.7 2.3 2.0 1.4

Banana 0–0.1 0.1–0.2 0.2–0.3 0.3–0.6

5.6 5.6 5.6 4.9

1.72 1.74 1.80 1.10

9.7 9.0 8.8 3.5

a

CS (%)

FS (%)

Silt (%)

Clay (%)

2 2 2 2

23 24 23 32

32 30 32 28

43 44 43 39

3 1 1 <1

32 33 33 26

25 26 23 33

40 40 43 41

Method codes for Rayment and Higginson (1992); OC, organic carbon (Walkley and Black); ECEC, effective cation exchange capacity; CS, coarse sand; FS, fine sand.

and 310 kg ha−1 for bananas in this region (Incitec Pivot Ltd., pers comm.; S. Lindsay pers comm.). The average annual N application in the banana industry was 520 kg−1 ha−1 in 1995, at which time no replicated N fertiliser trials had been conducted on bananas in Australia (Daniells, 1995). However, high concentrations and loads of N from sugarcane and banana production have been reported in streams and groundwater in the Johnstone and Tully River catchments within the Australian humid tropics (Armour et al., 2009; Hunter and Walton, 2008; Rasiah et al., 2005, 2010; Thorburn et al., 2003). Losses of N by deep drainage, which depend mostly on hydrology and fertiliser practice, have been measured by lysimeters, both disturbed and undisturbed, or estimated using models calculating hydrology and N movement (e.g. Goss and Ehlers, 2009; Thorburn et al., 2005, 2011). Under sugarcane, losses of nitrate to groundwater have ranged from <1 to 70 kg N ha−1 crop−1 in Australia, Brazil and Mauritius (Ng Kee Kwong and Deville, 1984; Bohl et al., 2001; de Oliveira et al., 2002; Gihberto et al., 2009; Rasiah et al., 2005, 2010; Thorburn et al., 2011; Webster et al., 2012). Under bananas, deep drainage is particularly variable spatially and temporally because of redistribution of rainfall by the canopy, especially re-direction into stem flow. Under the banana stem, drainage can be 6–24 times higher than in areas such as in the row away from the stem, and in the inter-row (Cattan et al., 2007; Sansoulet et al.,

2008). Furthermore, stemflow as a proportion of rainfall changes as the plants develop (Sansoulet et al., 2007). Loads of N in deep drainage under bananas ranged from 116 kg N ha−1 in 14 months (306 kg N ha−1 applied, Wakelin et al., 2011) to ∼210 kg ha−1 year−1 ˜ (∼420 kg N ha−1 applied, Munoz-Carpena et al., 2002). Thus losses of N from the root zone have a large range in sugarcane but are high in bananas. The aim of the work reported here was to quantify the leaching losses of N from a range of fertiliser practices over several seasons in sugarcane and bananas in the humid tropics of Australia. This was the first replicated N fertiliser experiment on bananas in the Australian humid tropics. 2. Methods 2.1. Commercial sugarcane site (Gordonvale) 2.1.1. Location and crop management Losses of N in deep drainage were measured in a commercial field from 2007 to 2010. The study site (Fig. 1) has a humid tropical climate with an average annual rainfall at the nearby Mulgrave Sugar Mill of 1958 mm. Most rain falls in a distinct wet season between December and May. The soil type is an Acidic, Dystrophic, Brown Dermosol (Table 1; Isbell, 1996). The sugarcane crop

Fig. 1. Site locality map.

70

J.D. Armour et al. / Agriculture, Ecosystems and Environment 180 (2013) 68–78

Fig. 2. Layout of lysimeters and associated equipment to generate vacuum and collect deep drainage.

was planted in October 2006 in single rows at 1.8 m spacing and grown without irrigation. Harvest dates over the study period were 5 September 2007, 1 July 2008, 30 July 2009 and 4 August 2010. The farmer applied nitrogen fertiliser over the study period at rates of 136 kg N ha−1 on 3/11/2007, 138 kg N ha−1 on 24/10/2008 and 148 kg N ha−1 on 8/11/2009. Nitrogen was applied as a commercial blend of urea and potassium chloride (29.9% N and 17.5% K). It was side-dressed at a depth of 75–100 mm on either side of the mound where the plant is located and covered with soil. 2.1.2. Deep drainage Twelve suction lysimeters, devices to sample soil water moving through the profile, were installed on 29 November 2006, with 3 under each of 2 plant rows (approximately 2 m apart) and 3 in each of 2 adjacent inter-rows (approximately 2 m apart). Sugarcane plants in the area of each lysimeter installation were dug up by hand, covered and kept moist until they were replanted over the lysimeters approximately 6 h later. Each lysimeter was installed in a hole excavated by a small excavator before backfilling by hand to return the soil in the original horizons and to the original bulk density. The base of the lysimeter was located at a depth of 1 m (Fig. 2). As 85% of root biomass has been reported to occur in the surface 0.6 m (Blackburn, 1984), N sampled at this depth is assumed to be lost from the root zone, although some water uptake by roots has been measured from as deep as 2.8 m (Smith et al., 2005). The lysimeters were made from PVC cylinders, 308 mm in diameter. Three ceramic cups (Cooinda Ceramics, Melbourne, Australia) were installed in the base, covered with a layer of fine silica to ensure good contact with the soil. Ceramic cups are suitable for sampling soil water for N studies and other studies have used repacked lysimeters (de Oliveira et al., 2002; Fares et al., 2009; Vandenbruwane et al., 2008). The ceramic cups were connected in parallel to a vacuum line that carried drainage water (leachate) to individual sample reservoirs installed at the edge of the field to avoid interference with commercial farm activities. The traps, which had a capacity of 9.7 L, equivalent to 130 mm of drainage, were buried 0.2 m below the soil surface to maintain the samples

at soil temperature. The vacuum was controlled by a falling column of water in a tower beside the water traps. A 12 V pump, which was connected to a battery charged by a solar panel, provided the vacuum in the water tower. The system was designed to provide a low and constant vacuum to the ceramic cups of approximately 16 kPa and hence simulate natural potentional gradients (Lentz, 2006). It has been used successfully in previous studies (McShane et al., 1993; Wakelin et al., 2011). The volume of drainage water was converted to a depth by dividing the volume by the surface area of the lysimeter. Deep drainage was collected from the lysimeters over the first wet season, but samples were discarded because of disturbance to the original banded fertiliser and subsequent fertiliser application by hand that did not represent normal farm practice. The sampling for analysis started in late 2007 by which time 1848 mm of rain had fallen since installation of the lysimeters. Sampling periods, from the first leaching event of the wet season until deep drainage ceased, were 14/12/07–27/3/08 in year 1, 28/12/08–16/2/09 in year 2 and 11/11/09–2/3/10 in year 3. Rainfall was ∼2840 mm in all years. Of this, 1474–2382 mm fell during the sampling periods (Table 3). Weekly rainfall for the sampling periods ranged between 0 and 543 mm (mean 160 mm). Leachate samples were regularly pumped out of the water traps (at least once per week and more often as required) and volumes recorded manually before freezing for later laboratory analysis. Despite the presence of diverse denitrifying microbial communities in similar soils (Wakelin et al., 2011), it has been shown that there was no loss of N by denitrification from a sample stored in the sample reservoir over a period of 28 days (Armour et al., unpublished data). Concentrations of N as oxidised N (NOx ) and ammonium (NH4 ) were measured by a continuous flow analyser procedure (Rayment and Higginson, 1992). N loads in leachate were calculated from the volume of leachate collected in the water traps and the concentrations measured. 2.1.3. WaterSense water balance model The WaterSense daily water balance model, developed for sugarcane (Inman-Bamber et al., 2007), was used to provide an independent estimate of deep drainage. Reference evapotranspiration (ET0 ) was derived from SILO-Datadrill (DERM, 1998), calculated using the FAO 56 Penman–Monteith formula (Allen et al., 1998). Daily rainfall was recorded by the farmer. WaterSense calculates three coefficients (Kc , Ke and Ks ) for transforming ET0 to daily actual crop evapotranspiration (ETC ). ETC = min((Kc · ET0 ), R) + Ke · ET0

(1)

where min (a, b) defines the lower of the two values and where crop transpiration coefficient, Kc = min(1.2(1 − exp(−0.38L))/0.9, 1.2), L is the leaf area index determined as in the APSIM model (Keating et al., 1999) and R is the daily root water supply and is the sum of (KLi ( Ai −  Mi ))*Di over all soil depths (n): R=



[(KLi (Ai − Mi )) ∗ Di ]

(2)

where KLi is the root water extraction coefficient (0–1) (Keating et al., 1999; Robertson et al., 1993), and ( Ai −  Mi ) is the difference between actual soil water content and the minimum that the plant can extract for each layer and Di is the depth of the soil (mm). For each soil layer,  A varies between saturated soil water content ( S ) and  M as water infiltrates from rainfall or irrigation depending on a selected runoff curve number or from an overlying layer depending on a selected saturated conductivity coefficient (0–1); and as roots extract water as determined by ETC and KL . When  A is greater than a predetermined drained upper limit ( D ), water will flow to the layer below or out of the root zone as drainage, at a rate governed by the conductivity coefficient.

J.D. Armour et al. / Agriculture, Ecosystems and Environment 180 (2013) 68–78

71

Table 2 Parameters for a Red Dermosol used in the WaterSense model. Layer

Cumulative depth (m)

Layer thickness (m)

M

D

S

 AD

KL

1 2 3 4 5 6

0.2 0.4 0.5 0.6 0.8 1.0

0.2 0.2 0.1 0.1 0.2 0.2

0.171 0.225 0.270 0.317 0.319 0.323

0.282 0.325 0.371 0.420 0.416 0.412

0.358 0.379 0.402 0.427 0.425 0.423

0.05 0.05 0.05 0.05 0.05 0.05

0.1 0.1 0.08 0.07 0.06 0.05

 M , minimum soil water content at which plants can extract;  D , drained upper limit;  S , saturated soil water content;  AD , water content of air dried soil; KL , root water extraction coefficient.

Water stress coefficient is derived by: Ks = min

 R



ETC

, 1.0

(3)

Evaporation coefficient (from soil surface), Ke , is based on the depth of water in the top soil layer in excess of the depth remaining after air drying (term 1 in Eq. (4)); and the fraction of radiation reaching the soil surface (remaining terms):

 Ke =

 min

3

(A − AD ) , 1.0 (S − AD )

(0.05 + exp(−0.38L) − T )

− 0.1(1 − exp(−0.38L)) + 0.1

(4)

where  AD is the water content of air-dried soil and T is the fraction of the soil surface covered by cane residue (trash). T = 0.8 for this simulation. Values of  and KL for a Red Dermosol for this simulation (Table 2) were those used by (Inman-Bamber et al., 2000). The conductivity coefficient for each layer was 0.5. 2.2. Banana N fertiliser experiment 2.2.1. Location and crop management The yield response and N losses in deep drainage were measured in a N fertiliser trial over the 1995–1997 period. The South Johnstone site (Fig. 1) has a humid tropical climate with annual average rainfall of 3300 mm, most of which falls between December and May. The soil is a Haplic, Dystrophic Brown Dermosol (Isbell, 1996). Bananas were planted on 16/11/1995 in double rows with 7 m spacing between centres of double rows, with the two rows 1.5 m apart and plant spacing of 1.7 m along the row, providing a plant density of 1680 plants ha−1 . Plants were grown for 2 crop cycles, referred to as plant and ratoon. The experiment was laid out as a randomised complete block design with 6 rates of applied N (0, 150, 300, 400, 500 and 600 kg N ha−1 crop cycle−1 , designated N0, N150, N300, N400, N500 and N600) and 4 replicates. At the time of planting, the industry average N application was 520 kg ha−1 year−1 . Plots consisted of 12 sample plants (6 in each double row) with two guard plants on the end of each plot which were 13.6 m long. There were additional guard plants at the end of rows and guard rows on the edges of the trial. The site had been cropped with bananas previous to the experiment but they were destroyed one year before planting this crop. A crop of forage sorghum was sown before the preceding wet season, and cut and removed from the site after 6 months of growth in an attempt to reduce soil nitrate concentrations. No N fertiliser had been applied for more than one year before planting the bananas. The trial area received a basal fertiliser dressing of a lime blend (CaCO3 with 5% MgO) at 5000 kg ha−1 and 100 kg P ha−1 as superphosphate, which were broadcast and incorporated prior to forming the mounds for planting. An additional application of the lime blend at 2500 kg ha−1 was applied to the mound in November 2006 by a commercial spreading contractor.

Nitrogen and potassium fertilisers were applied individually as urea and potassium chloride, respectively, via the irrigation water. The required fertiliser quantity for each plot was pre-dissolved in water then poured into dilution tanks situated in each plot. The irrigation system was then turned on to deliver the fertiliser via under-tree mini-sprinklers to the area of the planted rows. If extra irrigation was also required, the fertiliser application was scheduled to occur towards the end of the irrigation cycle to minimise movement of the fertiliser through the soil. The rates of fertiliser were calculated on the basis of plot area (95 m2 ) but only applied to the irrigation zone (50 m2 ). Fertiliser was applied in this way at fortnightly intervals commencing on 24/1/1996 until the completion of the trial. N and K were applied in proportion to expected growth (and assumed plant demand) for each fortnight. The expected rate of growth was based on data by Turner (1972) but with the time scale compressed by 6 months to account for faster plant growth with higher temperatures at South Johnstone. Lower rates of fertiliser were applied early in plant development compared to later when growth rates were higher. For example, N400 received 5 kg N ha−1 in January 1996 and 33 kg N ha−1 in May 1996. The mean harvest date was 9/1996 for the plant crop and 7/1997 for the ratoon crop. Rainfall during the lysimeter sampling period was 2702 mm in 8 months for the plant crop and 2808 mm in 10 months for the ratoon crop. Irrigation was applied equally to all treatments with the mini-sprinklers on 18 and 20 occasions for plant and ratoon crops with totals of 450 and 500 mm, respectively. 2.2.2. Deep drainage Eleven suction lysimeters were installed similarly to the sugarcane site in December 1995 after plant emergence to avoid damage to the young plants. They were located in one plot of each of the N0, N400 and N 600 treatments. In each plot, 3 lysimeters were installed in the plant row, again with the base at a depth of 1 m. For logistical reasons (particularly running vacuum lines for long distances), the 3 lysimeters for each N treatment were not located in separate plots and thus were not randomised replicates. An additional two were installed in the inter-row area (the 7 m strip between the double rows of plants) in one of the N0 plots. Collection of deep drainage started one month after installation, during which time 165 mm of rain had fallen. As the ‘effective’ depth of roots in bananas has been reported to be 0–0.4 m, sometimes 0–0.6 m, the lysimeters at 1 m were well below the root zone (Carr, 2009). Leachate samples were collected 66 and 51 times for the plant and ratoon crops, respectively. N loads in leachate were calculated for the plant and ratoon crops by adjusting for the area of N application (row) and the inter-row to determine losses on an area basis. 2.2.3. Agronomic measurements Date of bunch emergence for each plant in each crop was recorded. Bunches were harvested at weekly intervals, when the diameter of the middle three fingers of the outer whorl of the third hand from the proximal end was ≥3.7 cm, and weighed. Destructive harvests were made on plants with N400 from a separate area

J.D. Armour et al. / Agriculture, Ecosystems and Environment 180 (2013) 68–78

0.03 (0.01) 0.01 (<0.01) 0.04 (0.03) 9.2 (0.79) 0.6 (0.12) 7.1 (0.63) 1.14 (0.29) 0.13 (0.06) 1.46 (0.43) 1177 903 781 a

b

Standard errors are in parentheses. Loads are calculated assuming that the row and inter-row each represent half of the field area.

1026 (25) 614 (35) 691 (45) 2382 1474 1681 2805 2885 2822 14/12/07–27/3/08 28/12/08–16/2/09 11/11/09–2/3/10

93 (12) 71 (9) 117 (10)

a,b

NOx -N load (kg ha−1 year−1 ) Mean NOx -N conc. (mg L−1 )a

Drainage from WaterSense model (mm) Drainage from lysimeters (mm)a Rain in sampling period (mm)

1. 5/9/07–1/7/08 2. 1/7/08–30/7/09 3. 30/7/09–4/8/2010

3.1.2. Deep drainage under sugarcane Deep drainage measured in the lysimeters ranged from 614 to 1026 mm over the 3 years (Table 3) with no consistent differences between the row and inter-row lysimeters. Over the 3 years, there was <12% difference between the row and inter-row. For example, mean drainage in year 1 was 1072 mm (range 945–1183 mm) for the row and 980 mm (range 906–1039 mm) for the inter-row. Drainage as a proportion of rainfall, calculated assuming equal areas under the row and inter-row, was 21–37% (s.e. 1–3) of rain during the crop periods. However, the measured deep drainage for year 2 was an underestimate. In year 2, during the first 64 days after fertiliser application, there was 132 mm of well distributed rainfall (average 2 mm day−1 and maximum daily rainfall of 32 mm) and no deep drainage. From day 65 to day 81, when the first drainage event was captured, there was 596 mm of rain (537 mm in 3 days) and an average of 66 mm of drainage captured by the lysimeters

Rain for crop period (mm)

3.1.1. Sugarcane yields Yields of sugarcane from commercial harvesting in the studied field were 118, 117 and 95 Mg ha−1 (millable stalk fresh weight) in the 3 years. They were 8–42% higher than the district average yield (83, 87 and 88 Mg ha−1 for 2008–2010).

No. of samples (no. of sample times)

3.1. Sugarcane

Sampling periods

3. Results

Table 3 Deep drainage sampling details, rain, drainage and N concentrations and loads for sugarcane.

2.2.5. Statistical analyses A repeated measures analysis of variance using GenStat was used for plant data because of repeated measurements on the same plots. This analysis accounts for the non-uniform covariance structure of the repeated measurements by using a correction factor (Greenhouse and Geisser, 1959). Corrected F tests were constructed and used to test the significance of N treatment and time effects and interactions. Pairwise comparisons were done between means using protected LSD tests (also using the Greenhouse Geisser correction). The multiple lysimeters installed in N treatments were not replicates so means and standard errors, rather than analysis of variance, were calculated for deep drainage, NOx -N concentrations and N loads.

Mean NH4 -N conc. (mg L−1 )a

2.2.4. Soil measurements Soil samples were collected with a 75 mm auger at depths of 0–0.1, 0.1–0.2, 0.2–0.3, 0.3–0.45 and 0.45–0.6 m, before planting and approximately in the middle of the bunch harvest period each year. Pre-planting samples were composites from 3 cores taken in each replicate block, resulting in a total of 4 samples per depth increment over the whole trial site. Samples taken during the harvest periods were composites of 3 cores plot−1 from the row (in the middle of the double row) and 3 cores plot−1 from the inter-row, taken from the N0, N400 and N600 plots resulting in two composites samples (one row and one inter-row) for each depth in each plot in those treatments. All samples were analysed for pH (1:5 water), mineral N (NH4 and NO3 ), effective cation exchange capacity (ECEC) and particle size distribution, and samples from the pre-planting sampling and the N0 and N400 plots of the harvest time samplings were analysed for organic C (Walkley and Black) (Table 1; Rayment and Higginson, 1992).

0.13 (<0.01) 0.04 (<0.01) 0.24 (<0.01)

NH4 -N load (kg ha−1 year−1 )a,b

on 9 occasions. Plants (4 plants in the plant crop and 2 plants for ratoon crop) were dug out of the ground and soil was washed off the corm, but no attempt was made to recover roots. Plant parts were separated, weighed, sub-sampled for drying and laboratory analysis for N content. N uptake was calculated from the dry weight and N content.

Year/crop dates

72

J.D. Armour et al. / Agriculture, Ecosystems and Environment 180 (2013) 68–78

73

Fig. 4. NOx -N concentrations in deep drainage under sugarcane in years 1, 2 and 3 (mean of row and inter-row).

Fig. 3. Cumulative rain and deep drainage measured by lysimeters and calculated by WaterSense for sugarcane for the periods over which deep drainage occurred.

They were higher early in the sampling period, which was closest to the time of fertiliser application and low at the end of the sampling periods (<0.1 mg L−1 , Fig. 4, mean data). NOx -N concentrations were always higher in the inter-row than in the row; mean concentrations were 1.9 and 0.5 mg L−1 in year 1, 0.2 and <0.01 mg L−1 in year 2, and 2.7 and 0.4 mg L−1 in year 3, for the inter-row and row, respectively (data not presented). Mean concentrations were low in year 2 (0.13 mg L−1 ) compared to years 1 and 3 (1.13 and 1.46 mg L−1 , Table 3 and Fig. 4). NOx -N concentrations varied between lysimeters on any given date, even when the drainage volumes collected were fairly uniform. For example, in early January 2008, NOx -N concentrations were 0.7–4.1 mg L−1 for the row lysimeters and 1.9–7.3 mg L−1 for the inter-row and drainage was 68–129 mm. The mean ammonium-N concentration over 3 years was 0.02 mg L−1 , resulting in deep drainage loads of NH4 -N of <0.2 kg ha−1 year−1 over the 3 years and are ignored in further discussion. Loads of N moving below a depth of 1 m were 0.6–9.2 kg ha−1 year−1 over the 3 years (Table 3 and Fig. 5). Loads were similar in seasons 1 and 3, but much lower in year two. In year two, deep drainage was first sampled 81 days after fertiliser application and NOx concentrations were subsequently low. The deep drainage N load was underestimated in year 2 due to over-topping of the water traps in the first deep drainage event. However, even if the unsampled deep drainage is accounted for, the load was still low in that year. The amount of deep drainage not accounted for in the first event was approximately 233 mm (the difference between modelled and measured deep drainage during that period). Assuming that its NOx -N concentration was the same as the captured deep drainage, the unaccounted-for deep drainage N load was thus 0.4 kg ha−1 , resulting in a total cumulative load of 1 kg ha−1 in year 2. The deep drainage N loads over the 3 years

before the overflow protection device turned off the pump. Over this period, the deep drainage calculated by the WaterSense model was 221 mm. In contrast, the amount of rain that fell between fertiliser application and the first sampling of deep drainage in the other years was 188 mm over 41 days and 415 mm over 26 days for years 1 and 3, respectively. Deep drainage calculated by the WaterSense model was similar to the measured drainage, but higher, especially in year 2, in which ‘overtopping’ of the water traps and hence incomplete sampling of the drainage occurred (Table 3 and Fig. 3). 3.1.3. NOx -N concentrations and N loads in deep drainage under sugarcane NOx -N concentrations in deep drainage varied widely, from 0.001–20 mg L−1 for individual lysimeters (data not presented).

Fig. 5. Cumulative rainfall from day of fertiliser application and N loads in deep drainage for sugarcane in years 1, 2 and 3.

74

J.D. Armour et al. / Agriculture, Ecosystems and Environment 180 (2013) 68–78

Table 4 Nitrate-N concentrations in soil at planting and harvest for each banana crop at three different rates of N fertiliser. Depth (m)

0–0.1 0.1–0.2 0.2–0.3 0.3–0.45 0.45–0.6

Nitrate-N concentration (mg kg−1 ) at plant crop harvest (17/9/96)

Nitrate-N concentration (mg kg−1 ) at planting

63 (5) 66 (5) 57 (6) 53 (6) 43 (6)

Nitrate-N concentration (mg kg−1 ) at ratoon crop harvest (10/7/97)

0N

400 N

600 N

0N

400 N

600 N

1 (0.3) 1 (0.2) 1 (0.3) <1 <1

62 (4) 64 (12) 79 (1) 80 (5) 58 (14)

63 (7) 88 (10) 83 (3) 84 (2) 102 (8)

<1 <1 <1 <1 <1

40 (9) 20 (4) 16 (3) 17 (2) 22 (5)

59 (10) 43 (11) 39 (11) 34 (9) 43 (6)

Standard errors are in parentheses.

Table 5 Time to harvest, bunch weights and yield for banana plant and ratoon banana crops. Treatment (kg ha−1 )

N0 N150 N300 N400 N500 N600 LSD (P = 0.05) a b c

Plant crop (11/1995–9/1996)

Ratoon 1 (9/1996–7/1997)

Days P-BHa

Bunch weight (kg plant−1 )

Yieldb (kg plant−1 )

Days P-BHa

Bunch weight (kg plant−1 )

Yieldb (kg plant−1 )

317 320 315 306 313 314 ns

25.4 26.5 26.0 25.4 24.7 27.2 ns

26.4 27.2 27.1 27.2 26.0 28.4 ns

623c 620bc 593ab 582a 593ab 585a

40.5a 41.3ab 43.9ab 42.9ab 41.8ab 45.1b 3.8

44.6a 45.4ab 52.2bc 52.3bc 49.1abc 55.7cd 7.0

c

P-BH planting to bunch harvest. Yield of fruit = bunch weight × 0.9 to account for bunch stem weight and adjusted to a 1 year cycle. Means for this parameter have been back transformed so LSD values are inappropriate on this scale.

were equivalent to 0.4–7% of the fertiliser N applied (or 0.7–7% allowing for the unsampled deep drainage in year 2). 3.2. Bananas 3.2.1. Soil measurements Nitrate N concentrations in the soil at planting were very high (43–66 mg kg−1 ) and equivalent to 377 kg ha−1 to a depth of 0.6 m, assuming that the soil bulk density was 1200 kg m−3 (Table 4). By harvest time in both the plant and ratoon crops, nitrate-N concentrations for N0 were ≤1 mg kg−1 throughout the profile, reflecting the absence of N fertiliser inputs and losses including deep drainage and plant uptake. On the sampling dates closely following (14–19 days after) N application, nitrate-N concentrations were always lower for N400 than for N600. Soil pH after 18 months of cropping was reduced to 0.6 m depth by N fertiliser application. pH decline due to fertiliser application was a maximum of 1.3 units (difference between N0 and N600) at 0–0.1 m deep (Fig. 6).

Fig. 6. Soil pH in banana plots with 3 rates of applied N (0, 400, 600 kg ha−1 crop cycle−1 as urea) after 18 months of treatment.

3.2.2. Banana yield, growth and N uptake Bunch weights were ∼26 and ∼43 kg for the plant and ratoon crops, respectively, similar to those from local high yielding commercial crops (Table 5). The mean pseudostem height at harvest increased from 2.3 m in the plant crop to 3.3 m in the ratoon. Yield parameters in the plant crop did not respond to applied N, apart from height of following sucker at harvest, which was smaller for N0 than N600 (data not presented). The optimum rate of N in the plant crop was the lowest rate of applied N (150 kg ha−1 ). This application rate would ensure adequate heights of follower suckers and thereby avoid extended cropping period in subsequent ratoons with associated higher production costs. For the ratoon crop, the optimum N rate was 300 kg N ha−1 year−1 . N uptake by the plant (excluding the roots) for N400 was 218 kg ha−1 for the plant crop and 645 kg ha−1 for the ratoon (Table 6). Export of N in bunches and bunch stems was 57 and 128 kg ha−1 for the plant and ratoon crops. 3.2.3. Deep drainage under banana crop Deep drainage was higher in the plant crop than in the ratoon crop for similar quantities of rain and irrigation (Table 6). Mean deep drainage in the row ranged from 1757 to 2500 mm in the plant crop and from 1137 to 1662 mm in the ratoon crop. It was much lower in the inter-row (1273 and 659 mm for the plant and ratoon crops, respectively), with some of the difference attributed to the absence of irrigation in the inter-row (450 and 500 mm was applied to the plant row area for the plant and ratoon crops, respectively). Mean drainage in the row as a proportion of rain and irrigation was 65% for the plant crop and 37% for the ratoon. Variability among lysimeters was high in both the row and inter-row areas in both crop cycles, as indicated by the high standard errors of the mean. 3.2.4. NOx -N concentrations and loads in deep drainage under banana crop NOx -N concentrations in lysimeter samples varied with time from planting and with rate of applied N, once the initial high concentrations in the soil had fallen (Fig. 7). Concentrations were high (mean of 54 mg N L−1 in the first week) in all lysimeters in the first

J.D. Armour et al. / Agriculture, Ecosystems and Environment 180 (2013) 68–78

75

Table 6 Mean drainage, NOx -N concentration, N load, N uptake and export for banana plant and ratoon crops. N0

Drainage (mm) NOx -N concentration (mg L−1 ) N load in deep drainage (kg ha−1 ) Plant uptake of N (kg ha−1 ) N export in bunches (kg ha−1 )

N400

N600

Inter-row

Plant crop

Ratoon crop

Plant crop

Ratoon crop

Plant crop

Ratoon crop

Plant crop

Ratoon crop

1757 (312) 27 (6) 393 (20)

1137 (361) 3 (0.3) 32 (8)

2500 (61) 29 (8) 453 (39) 218 (3.4) 57 (5.1)

1383 (280) 38 (12) 218 (25) 645 (34) 128 (3.4)

2096 (158) 31 (5) 391 (29)

1662 (210) 90 (18) 675 (71)

1273(157) 33(1)

1662 (210) 7 (4)

Standard errors are in parentheses.

samples collected, including the inter-row, even before N application had commenced. This appears to be consistent with the high soil nitrate-N concentrations at planting. Concentrations in the fertilised plots decreased consistently over approximately 3 months to reach values <7 mg L−1 . From mid March to 1 July 1996, concentrations of NOx -N for N400 and N600 were similar. From July onwards, concentrations for N600 were always greater than N400. In the inter-row lysimeters, located where no fertiliser had been applied to the soil surface, NOx -N concentrations were between 5 and 64 mg L−1 until mid November 1996 when they decreased to <3 mg L−1 and remained low for the rest of the monitoring period. Concentrations of NH4 -N were usually <1 mg L−1 and loads were <3 kg ha−1 crop−1 (data not presented). Initially, loads of N measured in deep drainage were high in the plant crop and were not related to rate of N application (Table 6 and Fig. 8). They increased rapidly for all N treatments, from the first sampling until mid March 1996. After this, the loads for N0 increased only very slowly, to a cumulative total of 425 kg N ha−1 over both crops, while loads for N400 and N600 started to reflect N applications up to a total loss of 671 and 1066 kg N ha−1 , respectively. The N load attributable to N fertiliser, calculated by subtracting the load of N0, was 246 and 641 kg ha−1 , which was equivalent to 37 and 63% of the fertiliser application for N400 and N600 over 18 months (Fig. 8). 3.2.5. N balance in banana crop A partial N balance was calculated for the N400 treatment, for which plant uptake data was available. Outputs of N were 702 kg ha−1 in crop uptake (plant crop bunch export + ratoon crop uptake) and 671 kg ha−1 in deep drainage, adding to a total of 1373 kg ha−1 . As fertiliser input was 709 kg ha−1 , there was a net output of 664 kg ha−1 . This was partially explained by a decrease in profile nitrate-N of 183 kg ha−1 from the 0–0.6 m depth layer (assuming bulk density of 1200 kg m−3 ). Additional contributions to the net output may have been uptake from mineralised soil organic N and possibly also uptake from deeper than 0.6 m.

Fig. 7. NOx -N concentrations in deep drainage from banana plots (under the row) with different fertiliser treatments and under the inter-row (no fertiliser).

Additional losses of N in gaseous forms were possible but were not measured. 4. Discussion The amount of deep drainage in these well-drained soils varied according to the crop, even though climatic conditions were similar. Under the sugarcane, drainage was similar under the row and interrow, and comprised 22–37% of rainfall. Deep drainage calculated by the model, WaterSense, agreed closely with the amount measured in the lysimeters in two years, and most of the difference in the other year could be explained by under-sampling the first deep drainage of the wet season. This comparison indicates that the lysimeters were adequately capturing deep drainage. Under bananas, deep drainage was higher at 37–65% of rainfall plus irrigation, and more spatially variable. Drainage was less in the ratoon crop than in the plant crop. This is assumed to be the result of higher transpiration losses from the larger ratoon plants and possibly increased soil compaction from traffic during crop management operations. The high spatial and temporal variability is consistent with detailed research in the French West Indies on rain-fed banana fields (Cattan et al., 2007; Sansoulet et al., 2008). Irrigated and fertigated bananas are likely to have even greater variability because of the changing location of the stems of successive ratoons relative to the lysimeters and mini-sprinklers (delivering water and N) as the plants develop. For another tropical tree crop, oil palm, grown with similar high rainfall on permeable soils, high spatial variability in throughfall, stemflow, fertiliser application, infiltrability and uptake also led to very high spatial variability in nitrate concentrations (measured in suction cups) and leaching (Nelson et al., 2006; Banabas et al., 2008). Loads of N as NOx in deep drainage under bananas were high when high rates of N fertiliser were regularly applied to a site

Fig. 8. Cumulative inputs of N in fertiliser and loads of N in deep drainage with different N treatments, and cumulative rain and irrigation for banana plant and first ratoon crops.

76

J.D. Armour et al. / Agriculture, Ecosystems and Environment 180 (2013) 68–78

with an average weekly rainfall plus irrigation of 90 mm week−1 . We measured a net N load at a depth of 1 m of 246 kg ha−1 when 709 kg N ha−1 was applied over 18 months (N400). The agronomically optimum rate of fertiliser over this period would have been 450 kg ha−1 . Soil mineral N contents at the start of the trial were high despite the preceding sorghum catch crop, grown without N fertiliser. The N balance estimates also suggested that net mineralisation of organic N may have occurred over the 18-month plant-plus-ratoon crop period. Based on a measured decrease in organic C of 0.09% across the site and assuming a C:N ratio of 10:1, net mineralisation of N could be estimated at 617 kg ha−1 to 0.6 m depth. The number of soil samples taken was insufficient to be confident of such a loss of organic matter, but a large decline may have been possible due to large (unquantified) inputs of banana plant residues and sorghum root residues from the preceding crops. Using the same lysimeter technique on bananas in a similar soil in an adjacent catchment, Wakelin et al. (2011) reported an N load in deep drainage of 116 kg N ha−1 , equivalent to 38% of N inputs during the sampling period. In the Canary Islands, the N load ˜ was ∼210 kg ha−1 year−1 , equivalent to 50% of applied N (MunozCarpena et al., 2002). In contrast, N loads in deep drainage from sugarcane reported here were low (0.6–1 to 9.2 kg ha−1 ) from ratoon crops (i.e. plants with an established root system) that received average district N rates and in which deep drainage did not occur until 26–81 days after N application. The N loads are generally much lower than the range of 2–241 kg ha−1 reported for sugarcane in Queensland with higher application rates of fertiliser (144–247 kg N ha−1 , Reghenzani et al., 1996; Stewart et al., 2006; Thorburn et al., 2011). Other studies have reported N loads in deep drainage of 4.5–70 kg ha−1 in Brazil and Mauritius for fertiliser applications of 0–120 kg N ha−1 (Ng Kee Kwong and Deville, 1984; de Oliveira et al., 2002; Gihberto et al., 2009). The loads measured in this study are also lower than the average of 2–45 kg N ha−1 accession to groundwater estimated for the surrounding area under sugarcane (Rasiah et al., 2012). This may be due to higher rates of N application in surrounding farms, less favourable timing of fertiliser in relation to rain and possibly drainage from previous wet seasons. In bananas, deep drainage losses of N were closely related to the amount and timing of fertiliser application once the high initial soil nitrate concentrations had decreased. Despite the variability in deep drainage under bananas, the results clearly show that N is leached below the root zone in well-drained soils in a high rainfall environment when fertiliser applications exceed crop demand. This occurred even with fortnightly application and doses aligned to growth rate. For sugarcane, where fertiliser is restricted to one or two applications per year for economic reasons (labour and fuel costs), timing of fertiliser application in relation to leaching events is critical. Concentrations of NOx -N in water moving through the soil profile reached a maximum about 50–70 days after application of fertiliser, and then declined rapidly (Fig. 4). The pattern of decline was identical in the three crops, except that in year 2, deep drainage commenced much later (due to rainfall characteristics in that year), and hence the total deep drainage load was much lower. In our study, NOx -N concentrations in deep drainage were low for rainfed sugarcane (<2 mg L−1 ) but as high as 180 mg L−1 under irrigated bananas. NOx -N concentrations were always higher in the inter-row than in the row under sugarcane, which was presumably due to the inter-row lysimeters being located closer to the fertiliser bands inserted in the side of the mound. Low NOx -N concentrations throughout year 2 indicate that the under-sampled drainage event did not greatly underestimate N loads. The concentrations we measured under sugarcane and bananas were very similar to those reported elsewhere for sugarcane (1.7–5 mg L−1 , Bohl et al., 2001; Hesp et al., 2008; Gihberto et al., 2009) and sometimes higher than

˜ the range of 50–120 mg L−1 reported for rainfed bananas (MunozCarpena et al., 2002). The effect of N management, particularly the losses from rates in excess of plant demand, and the environmental implications for water quality and soil health, were well communicated to the banana industry over a 13-year period following the experiment described. Thus, this program is considered to have contributed to a decline since 1995 in the mean N usage by as much as 40%, to 310 kg N ha−1 year−1 . This reduction across the industry is equivalent to 1880 t year−1 . Additional factors likely to have also influenced the decline were an increase in N fertiliser prices by 1.5-fold between 1995 and 2005 (Incitec Pivot Ltd., pers. comm.) and in environmental awareness/pressure (e.g. Reef Water Quality Protection Plan, Anonymous, 2003). This reduction in fertiliser application rates has been achieved without apparent yield reduction, corresponding to the results of the N rate experiment reported here (Table 5). The industry N rate is now lower than that reported in other countries (e.g. 450–500 kg ha−1 year−1 in Canary Inlands, ˜ Munoz-Carpena et al., 2002; currently 400–500 kg ha−1 year−1 in Costa Rica, J. Daniells, unpublished data). However, N loss in deep drainage equivalent of 37% of the N applied in N400, in comparison to the recommended N application rate of 300 kg N ha−1 for ratoons, suggests that N rates could be further reduced if there was better alignment of fertiliser application and crop demand. Options include better use of weather forecasting and alternative products such as slow release fertiliser. N management in the sugar industry has also been the target of research and extension effort and N application rates in the humid tropics have declined from 151 kg ha−1 in 1996–1999 to 137 kg ha−1 (mean 2006–2009)(Incitec Pivot Ltd., pers. comm.). Catchment modelling in the nearby Tully–Murray catchment calculated that a 30% reduction in N application by the banana industry would reduce dissolved inorganic N loads in surface water from the banana industry by 27% (from 91 to 61 Mg year−1 , Armour et al., 2009). Movement of nitrate below 1 m does not necessarily mean that it then travels all the way to streams, as Wakelin et al. (2011) recently found diverse denitrifying microbial communities in water draining below sugarcane and banana fields. However, high concentrations and loads of N in streams draining areas of sugarcane and banana production have been reported widely in Queensland (e.g. Bainbridge et al., 2009) and elsewhere. This indicates that denitrification processes alone are insufficient to reduce N loads to a level that does not threaten the health of streams and the marine environment. Similarly, other research at the sugarcane site showed that the nearby forested riparian zone is likely to have a limited capacity to remove N from groundwater (Connor et al., 2012). In addition to causing high leaching losses, high rates of N fertiliser (in the form of urea or ammonium) application can cause soil acidification as a result of oxidation of NH4 + and generation of H+ (Helyar and Porter, 1989). Despite fortnightly application of urea and 2 applications of a lime blend, high rates of nitrate leaching acidified the soil under bananas to a depth of 0.6 m. While growth and yield of bananas was not affected, such acidification is a threat to sustainability, particularly for rotation crops that may not be as tolerant of acidity. Sub-soil acidity is difficult to correct with conventional liming programs, although alternative, more expensive nitrate fertilisers are effective in preventing acidification and raising the pH of acidified sub-soils (Armour et al., 2005). 5. Conclusions Loads of N in deep drainage from the root zone of sugarcane were generally low (0.6–1 to 9.2 kg N ha−1 wet season−1 ). The loads were

J.D. Armour et al. / Agriculture, Ecosystems and Environment 180 (2013) 68–78

lowest in the year with the longest period between fertiliser application and the first deep drainage event. In bananas, there were high concentrations of NOx -N and large loads of N in deep drainage from the root zone of bananas when N fertiliser rates exceeded plant demand. The close agreement in two of the three years between the amount of deep drainage from sugarcane measured by lysimetry and that calculated by the WaterSense daily water balance model indicates that the lysimeter system adequately captured deep drainage. Acknowledgements The Australian Research Council (LP0669439) and Horticulture Australia (FR95013) contributed to the funding for this work. We thank N.J. Bryde, T. Whiteing, M.J. Dwyer and D.E. Rowan for technical support in the field and laboratory, and S. Lindsay for leading the banana industry extension program. Mr B. Corcoran kindly allowed access to his sugarcane property and assisted with sample collection and providing production records. References Allen, R.G., Pereira, L.S., Dirk, R., Smith, M.S., 1998. Crop Evapotranspiration: Guidelines for Computing Crop Water Requirements: FAO Irrigation and Drainage Paper 56. FAO Natural Resources Management and Environment Department, Available from: http://www.fao.org/docrep/x0490e/x0490e00.htm (accessed 03.01.11). Anonymous, 2003. Reef Water Quality Protection Plan: For Catchments Adjacent to the Great Barrier Reef World Heritage Area. Queensland Department of Premier and Cabinet, Brisbane, The State of Queensland and Commonwealth of Australia, Available from: http://www.reefplan.qld.gov.au (accessed 18.02.11). Armour, J.D., Berthelsen, S., Ruaysoongnern, S., Moody, P.W., Noble, A.D., 2005. Remediation of soil acidification by form of nitrogen fertiliser on grass swards of Australia and Thailand. In: Final Proceedings of International Symposium on Management of Tropical Sandy Soils for Sustainable Agriculture, Khon Kaen, Thailand. Armour, J.D., Hateley, L.R., Pitt, G.L., 2009. Catchment modelling of sediment, nitrogen and phosphorus nutrient loads with SedNet/ANNEX in the Tully–Murray basin. Mar. Freshwater Res. 60, 1091–1096. Aulakh, M.S., Malhi, S.S., 2005. Interactions of nitrogen with other nutrients and water: effect on crop yield and quality, nutrient use efficiency, carbon sequestration, and environmental pollution. Adv. Agron. 86, 341–409. Bainbridge, Z.T., Brodie, J.E., Faithful, J.W., Sydes, D.A., Lewis, S.E., 2009. Identifying the land-based sources of suspended sediments, nutrients and pesticides discharged to the Great Barrier Reef from the Tully–Murray Basin, Queensland, Australia. Mar. Freshwater Res. 60, 1081–1090. Banabas, M., Turner, M., Scotter, D.R., Nelson, P.N., 2008. Losses of nitrogen fertiliser under oil palm in Papua New Guinea: 1. Water balance, and nitrogen in soil solution and runoff. Aust. J. Soil Res. 46 (4), 332–339. Blackburn, F., 1984. Sugar-cane. Longman, New York, ISBN 0-582-46028-X, p. 414. Bohl., H.P., Roth, C.H., Tetzlaff, D., Timmer, J., 2001. Estimation of groundwater recharge and nitrogen leaching under sugarcane in the Ripple Creek catchment, Lower Herbert. Proc. Aust. Soc. Sugar Cane Technol. 23, 84–89. Brodie, J., Binney, J., Fabricius, K., Gordon, I., Hoegh-Guldberg, O., Hunter, H., O’Reagain, P., Pearson, R., Quirk, M., Thorburn, P., Waterhouse, J., Webster, I., Wilkinson, S., 2008. Synthesis of Evidence to Support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef. The State of Queensland (Department of the Premier and Cabinet), Brisbane, Australia, Available from: http://www.reefplan.qld.gov.au/library/pdf/publications (accessed 21.02.11). Carr, M.K.V., 2009. The water relations and irrigation requirements of banana (Musa spp.). Expl. Agric. 45, 333–371. Cattan, P., Bussière, F., Nouvellon, A., 2007. Evidence of large rainfall partitioning patterns by banana and impact on surface runoff generation. Hydrol. Proc. 21, 2196–2205. Connor, S., Nelson, P.N., Armour, J.D., Henault, C., 2013. Hydrology of a forested riparian zone in an agricultural landscape of the humid tropics. Agric. Ecosys. Environ. 180, 111–122. Daniells, J.W., 1995. Results of a survey of research/development priorities and crop management practices in the north Queensland banana industry. QDPI Bulletin QB95001. Queensland Department of Primary Industries, Brisbane. de Oliveira, M.W., Trivelin, P.C.O., Boaretto, A.E., Muraoka, T., Mortatti, J., 2002. Leaching of nitrogen, potassium, calcium and magnesium in a sandy soil cultivated with sugarcane. Pesquisa Agropecuária Brasileira 37, 861–868. DERM (Queensland Department of Environment and Resource Management), 1998. The SILO Data Drill, Available from: http://www.longpaddock.qld.gov.au/silo/ (accessed 20.10.10).

77

Drigo, R., 2005. Trends and patterns of tropical land use change’. In: Bonell, M., Bruijnzeel, L.A. (Eds.), Forests, Water and People in the Humid Tropics. Cambridge University Press, pp. 9–39. Fares, A., Deb, S.K., Fares, S., 2009. Review of vadose zone soil solution sampling techniques. Environ. Rev. 17, 215–234. Gihberto, P.J., Libardi, P.L., Brito, A.S., Trivelin, P.C.O., 2009. Leaching of nutrients from a sugarcane crop growing on an ultisol in Brazil. Agric. Water Manage. 96, 1443–1448. Goss, M.J., Ehlers, W., 2009. The role of lysimeters in the development of our understanding of soil water and nutrient dynamics in ecosystems. Soil Use Manage. 25, 213–223. Greenhouse, S.W., Geisser, S., 1959. On methods in the analysis of profile data. Psychometrika 24, 95–112. Helyar, K.R., Porter, W.M., 1989. Soil acidification, its measurement and the processes involved. In: Robson, A.D. (Ed.), Soil Acidity and Plant Growth. Academic Press, Sydney, pp. 61–102. Hesp, C., Attard, S., Milla, R., Poggio, M., Davies, B., 2008. Evaluating Alternative Irrigation for a Greener Future, Available from: http://www.bbifmac.org.au/ assets/Final%20Report%20-%20EAI%20BDTNRM.pdf (accessed 17.02.11). Hunter, H.M., Walton, R., 2008. Land-use effects on fluxes of suspended sediment, nitrogen and phosphorus from a river catchment of the Great Barrier Reef, Australia. J. Hydrol. 356, 131–146. Inman-Bamber, N.G., Zund, P.R., Muchow, R.C., 2000. Water use efficiency and soil water availability for sugarcane. Proc. Aust. Soc. Sugar Cane Technol. 22, 264–269. Inman-Bamber, N.G., Attard, S.J., Verrall, S.A., Webb, W.A., Baillie, C., 2007. A webbased system for scheduling irrigation in sugarcane. Proc. Int. Soc. Sugar Cane Technol. 26, 459–464. Isbell, R.F., 1996. The Australian Soil Classification. CSIRO, Melbourne. Keating, B.A., Robertson, M.J., Muchow, R.C., Huth, N.I., 1999. Modelling sugarcane production systems: I. Description and validation of the APSIM Sugarcane module. Field Crops Res. 61, 253–271. Lentz, R.D., 2006. Automated system for collecting multiple, sequential samples from soil water percolation samplers under continuous vacuum. Commun. Soil Sci. Plant Anal. 37, 1195–1203. McDonald, G., Weston, N., 2004. Sustaining the Wet Tropics: A Regional Plan for Natural Resource Management, Volume 1. Background to the Plan. Rainforest CRC and FNQ NRM Ltd, Cairns, 80 pp. McShane, T.J., Reghnenzani, J.R., Prove, B.G., Moody, P.W., 1993. Nutrient balances and transport from sugarcane land – a preliminary report. Proc. Aust. Soc. Sugar Cane Technol. 15, 268–275. Moody, P.W., Reghenzani, J.R., Armour, J.D., Prove, B.G., McShane, T.J., 1996. Nutrient balances and transport at farm scale – Johnstone River Catchment. In: Hunter, H.M., Eyles, G.E., Rayment, G. (Eds.), Downstream Effects of Land Use. Department of Natural Resources, Brisbane, Australia. ˜ R., Ritter, A., Socorro, A.R., Pérez, N., 2002. Nitrogen evolution and Munoz-Carpena, fate in a Canary Islands (Spain) sprinkler irrigated banana plot. Agric. Water Manage. 52, 93–117. Nelson, P.N., Banabas, M., Scotter, D.R., Webb, M.J., 2006. Using soil water depletion to measure spatial distribution of root activity in oil palm (Elaeis guineensis Jacq.) plantations. Plant Soil 286, 109–121. Ng Kee Kwong, K.F., Deville, J., 1984. Nitrogen leaching from soils cropped with sugarcane under the humid tropical climate of Mauritius. Indian Ocean. J. Environ. Qual. 13, 471–474. Rasiah, V., Armour, J.D., Cogle, A.L., 2005. Assessment of variables controlling nitrate dynamics in groundwater: is it a threat to surface aquatic ecosystems? Mar. Pollut. Bull. 51, 60–69. Rasiah, V., Armour, J.D., Cogle, A.L., Florentine, S.K., 2010. Nitrate importexport in interacting groundwater-surface water systems under cropping in a wet-tropical environment. Aust. J. Soil Res. 48, 361– 370. Rasiah, V., Armour, J.D., Nelson, P.N., 2013. Nitrate in shallow fluctuating groundwater under sugarcane: coral reef health hazard and risk analysis. Agric. Ecosys. Environ. 180, 103–110. Rayment, G.E., Higginson, F.R., 1992. Australian Laboratory Handbook of Soil and Water Chemical Methods. Sydney, Inkata Press. Reghenzani, J.R., Armour, J.D., Prove, B.G., Moody, P.W., McShane, T.J., 1996. Nitrogen balances for sugarcane plant and first ratoon crops in the wet tropics. In: Wilson, J.R., Hogarth, D.M., Campbell, J.A., Garside, A.L. (Eds.), Sugarcane: Research Towards Efficient and Sustainable Production. CSIRO Division of Tropical Crops and Pastures, Brisbane, pp. 275–277. Robertson, M.J., Fukai, S., Ludlow, M.M., Hammer, G.L., 1993. Water extraction by grain sorghum in a sub-humid environment. II. Extraction in relation to root growth. Field Crops Res. 33, 99–112. Sansoulet, J., Cabidoche, Y.M., Cattan, P., 2007. Adsorption and transport of nitrate and potassium in an andosol under banana (Guadaloupe, French West Indies). Eur. J. Soil Sci. 58, 478–489. ˇ unek, ˚ J., 2008. SpaSansoulet, J., Cabidoche, Y.M., Cattan, P., Ruy, S., Sim tially distributed water fluxes in an andosol under banana plants: experiments and three-dimensional modeling. Vadose Zone J. 7, 819–829. Smith, D.M., Inmam-Bamber, N.G., Thorburn, P.J., 2005. Growth and function of the sugarcane root system. Field Crops Res. 92, 169–183. Stewart, L.K., Charlesworth, P.B., Bristow, K.L., Thorburn, P.J., 2006. Estimating deep drainage and nitrate leaching from the root zone under sugarcane using APSIMSWIM. Agric. Water Manage. 81, 315–334.

78

J.D. Armour et al. / Agriculture, Ecosystems and Environment 180 (2013) 68–78

Thorburn, P.J., Biggs, J.S., Attard, S.J., Kemei, J., 2011. Environmental impacts of irrigated sugarcane production: nitrogen lost through runoff and leaching. Agric. Ecosyst. Environ. 144, 1–12. Thorburn, P.J., Biggs, J.S., Weier, K.L., Keating, B.A., 2003. Nitrate in groundwaters of intensive agricultural areas in coastal Northeastern Australia. Agric. Ecosyst. Environ. 94, 49–58. Thorburn, P.J., Meier, E.A., Probert, M.E., 2005. Modelling nitrogen dynamics in sugarcane systems: recent advances and applications. Field Crops Res. 92, 337–351. Turner, D.W., 1972. Banana plant growth: 2. Dry matter production, leaf area and growth analysis. Aust. J. Exp. Agric. Anim. Husb. 12, 217–224. Vandenbruwane, J., De Neve, S., De Schrijver An Geudens, G., Verheyen, K., Hofman, G., 2008. Comparison of ceramic and polytetrafluoroethene/quartz suction cups

for sampling inorganic ions in soil solution. Commun. Soil Sci. Plant. Anal. 39 (7–8), 1105–1121. Wadley, R.L., Mertz, O., Chistensen, A.E., 2006. Local land use strategies in a globalising world – managing social and environmental dynamics. Land Degrad. Dev. 17, 117–121. Wakelin, S.A., Nelson, P.N., Armour, J.D., Rasiah, V., Colloff, M.J., 2011. Bacterial community structure and denitrifier (nirK gene) abundance in soil water and groundwater beneath agricultural land in tropical North Queensland, Australia. Aust. J. Soil Res. 49, 65–76. Webster, A.J., Bartley, R., Armour, J.D., Brodie, J.E., Thorburn, P.J., 2012. Reducing dissolved inorganic nitrogen in surface runoff water from sugarcane production systems. Mar. Pollut. Bull. 65, 128–135.