Michael Bell

• The University of Queensland

Simulation models are an important tool to predict how farming practices influence utilisation and loss of nitrogen (N). However, many simulation exercises lack sufficient validation of N dynamics from both soil and fertiliser sources and rely on single or a few measurable N pools, potentially shifting bias from one pool to another. This study eval...

Context The grain-growing areas of north-eastern Australia are a major producer of grain for human and livestock consumption, but declining soil nitrogen (N) and phosphorus (P) fertility is increasing fertiliser requirements to sustain productivity. Adding a concentrated zone of fertiliser P to the subsoil (i.e. a ‘deep P’ band) is an effective str...

Aims This study compared the ability of natural abundance (NA) and ¹⁵N-enrichment (EN) methods to quantify contribution of different N sources (fertilizer and legume N derived from fixation) to crop N uptake by maize crop grown in No-Till cropping system under field conditions. The quantitative estimates of different N contributions were then compa...

Cropping systems in many sub-tropical and tropical regions rely on phosphorus (P) fertilisers to maintain crop yields. However, crop responses are often spatially and temporally inconsistent. This study evaluated P availability from dispersed applications of fresh phosphate fertiliser and their residual effect in two contrasting Vertisols - a major...

Aims The aim of this study was to determine the effectiveness of natural (NatZeo) and acid-treated (AcidZeo) zeolites in increasing the nitrogen (N) recovery of sugarcane grown under conditions highly conducive for N losses. Methods This glasshouse trial replicated the pedoclimatic conditions typical of the Australian sugarcane industry in the Wet...

Fertiliser placement and type are key factors which regulate on-farm nitrogen (N) use efficiency. However, the interaction of these two management strategies is often overlooked. Efficacy assessments of enhanced efficiency fertilisers (EEFs) must consider the mode of application to not misinterpret outcomes and potentially limit EEF adoption. While...

Aims This study aims to compare the ability of natural abundance (NA) and ¹⁵N-enrichment (EN) methods to quantify N dynamics in a No-Till legume/non-legume maize crop rotation under field conditions; and deliver precise estimates of fertilizer N recovery across both rotations. Methods A field experiment was established on a Vertisol by sowing a le...

Context Agricultural soils are a major source of emissions of the greenhouse gas nitrous oxide (N2O). Aim Quantify direct N2O emissions from Australian agricultural production systems receiving nitrogen (N) inputs from synthetic and organic fertilisers, crop residues, urine and dung. Method A meta-analysis of N2O emissions from Australian agricul...

Vertisols are important cropping soils in tropical and sub‐tropical areas, but in many regions, decades of cropping has substantially reduced concentrations of plant‐available phosphorus (P), especially in the subsoil layers. Phosphorus behaviour in P‐depleted Vertisols has received comparatively little attention and the availability of P following...

Aims Increased subsoil water extraction through breeding of ‘designer’ root system architecture (RSA) may improve crop performance and resilience in the face of climate change (i.e. changing seasonal rainfall patterns). However, in many dryland environments, root systems face both water and nutrient scarcity (e.g. phosphorus (P)), with both resourc...

Enhanced efficiency fertilizer (EEF) technologies that employ product coatings to delay nitrogen (N) release or are chemically stabilized to inhibit key steps of N transformations in soil offer potential for improving N use efficiency (NUE) in agricultural systems. However, the dynamics of N release and transformation from single technologies may r...

Purpose We questioned how root ideotypes selected for deep or shallow root architecture function in complex environments with heterogeneous distributions of phosphorus (P), such as in many cropping systems in north-eastern Australia. Methods We used the rhizobox method to evaluate how contrasting genotypes of durum wheat and sorghum (wide and narr...

Purpose Selection for root traits has become a target in (pre-)breeding programs aiming at improving crop ability to capture soil resources. However, the benefit of selected traits in heterogeneous target environments will depend on spatial and temporal interactions between root systems, the soil environment (fertility and water supply) and managem...

In order to improve crop nutrition, phosphorus (P) fertiliser is increasingly being applied in concentrated bands. Although information is available regarding the sequence of reactions that occur within the band itself, comparatively little is known regarding the reactions controlling P diffusion and availability further away from fertiliser bands....

Enhanced efficiency fertilizer (EEF) technologies that employ product coatings to delay nitrogen (N) release or are chemically stabilized to inhibit key steps of N transformations in soil, offer potential for improving N use efficiency (NUE) in agricultural systems. However, the dynamics of N release and transformation from single technologies may...

Nitrogen (N) fertiliser inputs represent one of the largest variable costs in dryland cropping systems, and a key determinant of water-limited yield. Despite extensive research into microbial N losses via intermediate denitrification products such as N2O, limited research exists on total N losses, and the effect of increasing soil N surplus has on...

Polymer-coated urea (PCU) has been traditionally used for broadcast and/or incorporated application of nitrogen (N) fertilizers. To improve N use efficiency (NUE), there has been an increase in sub-surface banded application of this fertilizer technology. However, there is little information on the release and supply of N from PCU granules when app...

There is a global imperative to satisfy the demand for grain production and minimize environmental impacts associated with applying nitrogen (N) fertilizers. Soil is critical to the regulation of N supply and loss from agricultural systems. We summarize field-based measurements of these pathways for Australian dryland (rainfed) grain cropping soils...

Australian cotton production predominantly occurs on Vertisols. The average lint yield of cotton grown in Australia is 2 260–2 700 kg·hm−2, which is 2.5 to 3 times the world average. This high productivity per unit of land area requires efficient use of resources such as water and nutrients. However, high yields accelerate the export of nutrients s...

Background and Objectives This field and glasshouse study evaluates the relative effectiveness of agronomic zinc biofortification strategies to increase the Zn concentration in sweetcorn ( Zea mays ) kernels for human health, using applications of Zn fertilizer to the root‐zone or to foliage. Findings Plants accumulated additional Zn as the rate o...

The 15 N natural abundance (NA) method is increasingly used to quantify fertiliser N recovery by crops, even though this method does not always provide comparable results to those obtained using 15 N-enrichment (EN). This study assessed the ability of both methods to quantify urea-N recovery by maize (Zea mays) in soils with different management hi...

Anyone clicking on this link before July 04, 2021 will be taken directly to the final version of the article on ScienceDirect, which they are welcome to read or download. https://authors.elsevier.com/c/1d4KY3p6oQ6~3 The factors affecting chemical transformations of phosphorus (P) in highly concentrated fertilizer bands have received little attent...

PurposeTo conduct a field-based, integrated assessment of the effect of band-applied, polymer-sulfur coated urea (PSCU), plant oil coated urea (POCU), and polymer coated urea (PCU) on (i) the release dynamics of urea-N and mineral N in the soil profile (Experiment 1); and (ii) the crop N recovery and agronomic response of an irrigated maize crop (E...

Selection for root system architectures (RSA) to match target growing environments can improve yields through better adaptation to water and nutrient-limiting conditions in grain legume crops such as mungbean. In this study, the architectural development of root systems in four contrasting mungbean varieties was studied over time to explore their r...

‘Stabilised’ nitrogen (N) represents an important category of enhanced efficiency fertilizers (EEFs) in which chemicals added to urea granules inhibit target soil N transformation processes in order to optimize N availability for crop uptake. However the mechanistic understanding of how these inhibitors perform when urea-based fertilizers are bande...

The exchangeable fraction of soil potassium (K) has been viewed as the most important source of plant-available K, with other sources playing smaller roles that do not influence the predictive value of a soil test. Thus, as K mass balance changes, the soil test should change correspondingly to be associated with greater or reduced plant availabilit...

There are many terms used to define aspects of potassium (K) use efficiency of plants. The terms used most frequently in an agricultural context are (1) agronomic K use efficiency (KUE), which is defined as yield per unit K available to a crop and is numerically equal to the product of (2) the K uptake efficiency (KUpE) of the crop, which is define...

The purpose of this chapter is to describe how bioavailable soil K is assessed or predicted by soil tests. Soil testing commonly refers to the collection of a sample of soil representative of a field or agronomic management unit and, by way of extraction using chemical reagents, determination of the quantity of a nutrient that can be related to pla...

Soil potassium (K) has traditionally been portrayed as residing in four functional pools: solution K, exchangeable K, interlayer (sometimes referred to as “fixed” or “nonexchangeable”) K, and structural K in primary minerals. However, this four-pool model and associated terminology have created confusion in understanding the dynamics of K supply to...

Plants acquire K ⁺ ions from the soil solution, and this small and dynamic pool needs to be quickly replenished via desorption of surface-adsorbed K from clay minerals and organic matter, by release of interlayer K from micaceous clay minerals and micas, or structural K from feldspars. Because of these chemical interactions with soil solid phases,...

Placement strategies can be a key determinant of efficient use of applied fertilizer potassium (K), given the relative immobility of K in all except the lightest textured soils or high rainfall environments. Limitations to K accessibility by plants caused by immobility in the soil are further compounded by the general lack of K-stimulated root prol...

A range of enhanced efficiency fertilizers (EEFs) have been developed in response to widespread recognition of poor nitrogen (N) use efficiency (NUE) in agriculture; however, their effective utilization is not properly understood when applied in sub-surface bands. This study quantified soil chemical changes and the distribution of N species that ar...

The Australian sugar industry is facing mounting pressure to reduce the nitrogen (N) losses and nitrous oxide (N2O) emissions associated with N fertiliser use. Research has shown that N2O emissions from sugarcane (Saccharum officinarum L.) cropping systems can be reduced with the use of fertilisers coated with nitrification inhibitors, or by sowing...

This study explores the potential for genetic biofortification of sweetcorn (Zea mays L.) by quantifying immature kernel zinc (Zn) concentrations across a broad range of Zea mays L. germplasm. Varieties examined included commercial sweetcorn cultivars, high zeaxanthin sweetcorns, purple sweetcorns, blue maize, quality protein maize and popcorns. Th...

Root architecture is a promising breeding target for developing resource-efficient crops. Breeders and plant physiologists have called for root ideotypes that have narrow, deep root systems for improved water and nitrate capture, or wide, shallower root systems for better uptake of less mobile topsoil nutrients like phosphorus. Yet evidence of rela...

Phosphorus (P) is increasingly being applied in concentrated bands to satisfy plant nutrient requirements. To quantify changes in plant-available P in the fertosphere of highly concentrated fertilizer bands, we conducted a soil–fertilizer incubation experiment using seven soil types, three highly water-soluble P sources [monocalcium phosphate (MCP)...

Grain yield and mineral nutrient concentration in cereal crops are usually inversely correlated, undermining biofortification efforts. Sink size, expressed as kernel number per cob, was manipulated by controlling the time when the silks of sweetcorn (Zea mays) cv. Hybrix 5 and var. HiZeax 103146 were exposed to pollen. Twelve other varieties were m...

In recent years phosphorus application methods have become an important management strategy for optimising the uptake of the immobile nutrient phosphorus (P). Root system architecture (RSA) could play a particularly important role in the uptake of P by grain legumes, due to their relatively coarse root systems. The objective of this study was to un...

Critical ranges for soil tests are based on results that inevitably involve some broad variance around the fitted relationship. Some of the variation is related to field-based factors affecting crop response to nutrients in the soil and some to the efficiency of the soil-test extractant itself. Most attempts to improve soil tests focus on the extra...

Background and aims: Understanding the speciation of Zn in edible portions of crops helps identify the most effective biofortification strategies to increase the supply of nutrients for improving the health and nutrition of consumers. Methods: Kernels of twelve sweetcorn and three maize (Zea mays) varieties were analysed for Zn concentration and...

Main conclusion In sweetcorn (Zea mays L.), embryo Zn is accumulated mainly as Zn-phytate, whereas endosperm Zn is complexed with a N- or S-containing ligand. Understanding the speciation of Zn in crop plants helps improve the effectiveness of biofortification efforts. Kernels of four sweetcorn (Zea mays L.) varieties were analysed for Zn concentra...

Enhanced efficiency fertilisers (EEFs) may have an important role in improving nitrogen (N) use efficiency in agricultural systems. The performance of EEFs when applied by broadcasting and incorporation is well documented; however, little information is available for sub-surface banded N-fertiliser. This study aimed to determine the effectiveness o...

Background and aims: Understanding the spatial distribution of inorganic nutrients within edible parts of plant products helps biofortification efforts to identify and focus on specific uptake pathways and storage mechanisms. Methods: Kernels of sweetcorn (Zea mays) variety 'High zeaxanthin 103146' and maize inbred line 'Thai Floury 2' were harv...

Farmers often resort to an occasional tillage (strategic tillage (ST)) operation to combat constraints of no-tillage (NT) farming systems. There are conflicting reports regarding impacts of ST and a lack of knowledge around when, where and how ST is implemented to maximise its benefits without impacting negatively on soil and environment. We establ...

The traditional soil potassium (K) testing methods fail to accurately predict K requirement by plants. The Diffusive Gradients in Thin-films (DGT) method is promising, but the relationship between the DGT-measured K pool and plant available K is not clear. Wheat (Triticum aestivum L., cv. Frame) was grown in 9 Australian broad acre agricultural soi...

Intensive tillage, high fertiliser inputs, and plastic mulch on the soil surface are widely used by vegetable growers. A field investigation was carried out to quantify the impact of alternate land management and fertiliser practices designed to improve offsite water quality on the productivity of vegetable rotations within a sugarcane farming syst...

Intensive agricultural practices in farming systems in eastern Australia have been identified as a contributor to the poor runoff water quality entering the Great Barrier Reef (GBR). A field investigation was carried out to measure the off-farm water quality and productivity in a coastal farming system in northeastern Australia. Two vegetable crops...

The Australian Great Barrier Reef (GBR) is one of the world's best known natural ecosystems (Devlin and Schaffelke 2012). The catchments that drain into the GBR are best known for productive agricultural land that supports extensive grazing enterprises as well as croplands supporting sugarcane (Saccharum spp.), banana (Musa spp.), vegetables, cotto...

Cereal, legume and fibre crops grown on Vertosols formed in-situ on upland slopes in NE Australia have demonstrated greater yield responses to deep-placement (≈ 0.20 m) of K and P together, rather than just K alone. Beginning in 2013, eight sites were established across central and southern Queensland and northern New South Wales. Treatments consis...

Full text is available in the link below http://www.jswconline.org/content/71/5/109A.full.pdf+html

Grain sorghum grown in north-eastern Australia’s cropping region increasingly requires nitrogen (N) fertiliser to supplement the soil available N supply. The rates of N required can be high when fallows between crop seasons are short (higher cropping intensities) and when yield potentials are high. Fertiliser N is typically applied before or at cro...

Herbicide runoff from cropping fields has been identified as a threat to the Great Barrier Reef ecosystem. A field investigation was carried out to monitor the changes in runoff water quality resulting from four different sugarcane cropping systems that included different herbicides and contrasting tillage and trash management practices. These incl...

23% of global agricultural land are situated in the subtropics. Nitrous oxide (N2O) emissions were estimated to be higher under subtropical than under temperate climates. So mitigation of N2O emissions from subtropical farming systems can make an important contribution to reducing global warming. Accordingly, in this study we explored long-term N2O...

The DAYCENT biogeochemical model was used to investigate how the use of fertilizers coated with nitrification inhibitors and the introduction of legumes in the crop rotation can affect subtropical cereal production and N 2 O emissions. The model was validated using comprehensive multi-seasonal, high-frequency dataset from two field investigations c...

Alternative sources of N are required to bolster subtropical cereal production without increasing N2O emissions from these agro-ecosystems. The reintroduction of legumes in cereal cropping systems is a possible strategy to reduce synthetic N inputs but elevated N2O losses have sometimes been observed after the incorporation of legume residues. Howe...

Development of no-tillage (NT) farming has revolutionized agricultural systems by allowing growers to manage greater areas of land with reduced energy, labour and machinery inputs to control erosion, improve soil health and reduce greenhouse gas emission. However, NT farming systems have resulted in a build-up of herbicide-resistant weeds, an incre...

A multi-season 15N tracer recovery experiment was conducted on an Oxisol cropped with wheat, maize and sorghum to compare crop N recoveries of different fertilisation strategies and determine the main pathways of N losses that limit N recovery in these agroecosystems. In the wheat and maize seasons, 15N-labelled fertiliser was applied as convention...

Solution P-31 nuclear magnetic resonance (NMR) spectroscopy on sodium hydroxide-ethylenediaminetetraacetic acid (NaOH-EDTA) extracts can provide detailed characterization of soil organic P, but has not been previously applied widely to Vertisols. Vertisol soils were collected at two depths (0-10 cm and 10-30 cm) for chemical and spectroscopic analy...

Experiments were established in the Burdekin Irrigation Area in North Queensland, Australia, to measure whether yield improvements from breaking the sugarcane monoculture or fumigating the soil could be modified by the application of different rates of nitrogen (N) fertiliser. Experiments were conducted in consecutive crop cycles (phase 1, planted...

Recent studies report low and variable phosphorus (P) fertiliser use efficiency (PUE) for cotton in the northern grains region (NGR) of eastern Australia. This may be due to cotton accessing P pools that are not currently tested for in the subsoil (10–30 cm) or variation in response to P source and placement strategy. Two glasshouse studies were us...

Soil testing remains a most valuable tool for assessing the fertiliser requirement of crops. The relationship between soil tests (generally taken from surface soil) and relative yield (RY) response to fertiliser is subject to the influence of environment (e.g. water, temperature) and management (e.g. cultivation, sowing date). As such, the degree o...

The Better Fertiliser Decision for Crops (BFDC) National Database holds historic data for 356 potassium (K) fertiliser rate experiments (431 treatment series) for different rain-fed grain crops and soil types across Australia. Bicarbonate-extractable K (Colwell soil-test K) is the most extensively used soil test reported in the database. Data are a...

More than 1200 wheat and 120 barley experiments conducted in Australia to examine yield responses to applied nitrogen (N) fertiliser are contained in a national database of field crops nutrient research (BFDC National Database). The yield responses are accompanied by various pre-plant soil test data to quantify plant-available N and other indicator...

Australian cropping systems are dominated by winter cereals; however, grain legumes, oilseeds and summer cereals play an important role as break crops. Inputs of phosphorus (P) fertiliser account for a significant proportion of farm expenditure on crop nutrition, so effective fertiliser-use guidelines are essential. A national database (BFDC Nation...

The use of sugarcane trash (tops and residue) retention systems has been reported to lead to increases in total soil organic carbon (TOC) stocks. However, these increases have generally been small and confined to the top 0.05 m of the soil profile. It has been hypothesised that the amount of TOC sequestered could be increased if the intensive tilla...

Research both nationally and internationally has indicated that no-till (NT) management used in combination with stubble retention has the potential to increase soil organic carbon (SOC) stocks in cropping soils relative to conventional tillage (CT). However, rates of SOC increase can vary depending on cropping system, climate, and soil type, makin...

PRODUCERS IN THE Bundaberg/Childers and Maryborough districts are implementing various combinations of legume rotations, trash retention, reduced tillage and controlled traffic in new and evolving farming systems. There are challenges in successfully integrating these components. Two trial sites were established to measure the impact of different t...

Experiments involving breaks to the sugarcane monoculture, soil fumigation and the application of biocides were conducted in Bundaberg, the Burdekin Valley and at Tully, three sugarcane-growing regions in Queensland, Australia. The aim was to elucidate the cause(s) of previously observed positive yield responses to breaks in the monoculture and ass...

Yield decline has been a major issue limiting productivity improvement in the Australian sugar industry since the early 1970s and is suspected to be largely due to growing sugarcane in a long-term monoculture. In order to address this issue, rotation experiments were established in several sugarcane-growing regions in Queensland, Australia, to asce...

Most Australian sugarcane crops are harvested green, with the crop residues left behind after harvest remaining on the soil surface as mulch, a process known as green cane trash blanketing. Sampling in trash-blanketed sugarcane fields showed that roots were present to a depth of 150 cm, but that more than 90% of the root biomass was in the upper 30...

The impact of three cropping histories (sugarcane, maize and soybean) and two tillage practices (conventional tillage and direct drill) on plant-parasitic and free-living nematodes in the following sugarcane crop was examined in a field trial at Bundaberg. Soybean reduced populations of lesion nematode {Pratylenchus zeae) and root-knot nematode [Me...

LESION nematode (Pratylenchus zeae) occurs in almost every sugarcane field in Queensland and is perhaps the most important of a community of nematode pests that cost the Australian sugar industry an estimated $82 million/annum in lost production. Legumes such as soybean and peanut are relatively poor hosts of the nematode and, when they are used as...

THE IMPACT of three cropping histories (sugarcane, maize and soybean) and two tillage practices (conventional tillage and direct drill) on plantparasitic and free-living nematodes in the following sugarcane crop was examined in a field trial at Bundaberg. Soybean reduced populations of lesion nematode (Pratylenchus zeae) and root-knot nematode (Mel...

THE IMPACT of cropping histories (sugarcane, maize and soybean), tillage practices (conventional tillage and direct drill) and fertiliser N in the plant and 1st ratoon (1R) crops of sugarcane were examined in field trials at Bundaberg and Ingham. Average yields at Ingham (Q200A) and Bundaberg (Q151A) were quite similar in both the plant crop (83 t/...

Surface losses of nitrogen from horticulture farms in coastal Queensland, Australia, may have the potential to eutrophy sensitive coastal marine habitats nearby. A case-study of the potential extent of such losses was investigated in a coastal macadamia plantation. Nitrogen losses were quantified in 5 consecutive runoff events during the 13-month s...

It has been reported that high-density planting of sugarcane can improve cane and sugar yield through promoting rapid canopy closure and increasing radiation interception earlier in crop growth. It is widely known that the control of adverse soil biota through fumigation (removes soil biological constraints and improves soil health) can improve can...

The promotion of controlled traffic (matching wheel and row spacing) in the Australian sugar industry is necessitating a widening of row spacing beyond the standard 1.5 m. As all cultivars grown in the Australian industry have been selected under the standard row spacing there are concerns that at least some cultivars may not be suitable for wider...

Controlled traffic (matching wheel and row spacing) is being promoted as a means to manage soil compaction in the Australian sugar industry. However, machinery limitations dictate that wider row spacings than the standard 1.5-m single row will need to be adopted to incorporate controlled traffic and many growers are reluctant to widen row spacing f...

Negative potassium (K) balances in all broadacre grain cropping systems in northern Australia are resulting in a decline in the plant-available reserves of K and necessitating a closer examination of strategies to detect and respond to developing K deficiency in clay soils. Grain growers on the Red Ferrosol soils have increasingly encountered K def...

SOIL MICROBES are the main drivers of nutrient turnover processes, including conversion of trash blankets and fertilisers which provide nutrients to the crop. Soil biology impacts positively and negatively on the well-being of crops. There is little understanding of how crop management affects soil biology, yet optimising microbial processes should...