Nutrient recommendation frameworks are underpinned by scientific understanding of how nutrients cycle within timespans relevant to management decision-making. A trusted potassium (K) recommendation is comprehensive enough in its components to represent important differences in biophysical and socioeconomic contexts but simple and transparent enough for logical, practical use. Here we examine a novel six soil-pool representation of the K cycle and explore the extent to which existing recommendation frameworks represent key plant, soil, input, and loss pools and the flux processes among these pools. Past limitations identified include inconsistent use of terminology, misperceptions of the universal importance and broad application of a single soil testing diagnostic, and insufficient correlation/calibration research to robustly characterize the probability and magnitude of crop response to fertilizer additions across agroecozones. Important opportunities to advance K fertility science range from developing a better understanding of the mode of action of diagnostics through use in multivariate field trials to the use of mechanistic models and systematic reviews to rigorously synthesize disparate field studies and identify knowledge gaps and/or novel targets for diagnostic development. Finally, advancing evidence-based K management requires better use of legacy and newly collected data and harnessing emerging data science tools and e-infrastructure to expand global collaborations and accelerate innovation. S. M. Brouder (*) · J. J. Volenec Department of Agronomy, Purdue University, West Lafayette, IN, USA e-mail: sbrouder@purdue.edu; jvolenec@purdue.edu T. S. Murrell Department of Agronomy, Purdue University, West Lafayette, IN, USA African Plant Nutrition Institute and Mohammed VI Polytechnic University, Ben Guerir, Morocco e-mail: s.murrell@apni.net © The Author(s) 2021 T. S. Murrell et al. (eds.), Improving Potassium Recommendations for Agricultural Crops, https://doi.org/10.1007/978-3-030-59197-7_1 1 1.1 Overview of the Potassium Cycle Nutrient recommendation frameworks are underpinned by scientific understanding of how nutrients cycle within timespans relevant to management decision-making. The cyclic nature of K transfers and transformations in crop production can be shown by a diagram depicting pools of K in the soil-plant system and the fluxes of K between those pools within a given volume of soil for a specified period of time (Fig. 1.1). Time scales typically reference a crop within a season or a sequence of crops within a relatively short period of time (2–4 years) for which a single or small suite of interrelated management decisions will be made. The horizontal spatial extent may range from an individual plant to an entire farm enterprise but traditionally has emphasized the “field scale,” reflecting a farmer’s predetermined management unit. The vertical spatial boundaries typically range from the top of the crop canopy down into the soil to the depth of crop rooting. Therefore, the spatial and temporal extents of interest include all system components that are intrinsic to the soil and the site as well as those that are influenced by management and crop development. Together, these components directly influence crop productivity. Pools in the K cycle (Fig. 1.1) are categorized as inputs (pool 1), outputs (pools 2–5), plant pools within the cycle boundaries (pools 6–7), and those within the soil Soil surface 1. K inputs 2. Harvested plant K 4. Erosion and runoff losses of K 11. Interlayer K in micas and partially weathered micas Depth of rooting volume 6. Plant K 7. Unharvested plant K 8. Soil solution K 9. Surfaceadsorbed K 10. Interlayer K in secondary layer silicates 13. K in neoformed secondary minerals 12. Structural K in feldspars 5. Leached K K input K output flux plant K soil K 3. Open burning losses of K pools 8-13 can also be lost through erosion (fluxes not shown) Time scale: a cropping season Spatial scale: cumulative rooting volume for a crop Fig. 1.1 The K cycle. Pools are denoted by rectangles and are quantities of K in one or more types of locations. Fluxes are denoted by arrows and are movements of K from one pool to another. This cycle depicts six pools of soil K (referenced herein as the six soil-pool model) 2 S. M. Brouder et al.

After more than a century of cultivation and more than 80 years since the first field experiments on fertilizer use, there seems to be sufficient knowledge of oil palm mineral nutrition to support a productive and profitable industry. Still, changing conditions, especially in view of the allotment of new cultivation areas, newly developed genetic material, social and technological developments and consequential management changes, climatic changes, and so on, we summarize here the accessible information on mineral nutrition in mature Tenera oil palm generated over the past 50 years. We attempt to provide information that is both scientifically sound and practically relevant in order to bridge the gap between fundamental research and plantation management. Our scope covers an overview of oil palm development and adverse conditions, with a specific focus on plant nutrition. We shed light on the current understanding of yield potential and the origin of yield gaps and discuss the role nutrition plays in improved oil palm performance, including current systems to assess appropriate nutritional status. This leads to surveying information on nutrient deficiency effects and to an analysis of the applicability of and existing knowledge gaps in the 4R nutrient stewardship concept. We end with a comprehensive analysis regarding knowledge gaps and research opportunities and give a brief outlook into potential future research pathways.

Elevated CO2 stimulates crop yields but leads to lower tissue and grain nitrogen concentrations [N], raising concerns about grain quality in cereals. To test whether N fertiliser application above optimum growth requirements can alleviate the decline in tissue [N], wheat was grown in a Free Air CO2 Enrichment facility in a low-rainfall cropping system on high soil N. Crops were grown with and without addition of 50-60 kg N/ha in 12 growing environments created by supplemental irrigation and two sowing dates over 3 years. Elevated CO2 increased yield and biomass (on average by 25%) and decreased biomass [N] (3%-9%) and grain [N] (5%). Nitrogen uptake was greater (20%) in crops grown under elevated CO2. Additional N supply had no effect on yield and biomass, confirming high soil N. Small increases in [N] with N addition were insufficient to offset declines in grain [N] under elevated CO2. Instead, N application increased the [N] in straw and decreased N harvest index. The results suggest that conventional addition of N does not mitigate grain [N] depression under elevated CO2, and lend support to hypotheses that link decreases in crop [N] with biochemical limitations rather than N supply.

The objective of this study was to investigate the effect of elevated (550 +/- 19 mu mol mo1(-1)) [CO2] on uptake and utilization of nitrogen (N), phosphorus (P) and potassium (K) by soybean (Glycine max (L.) Merr) at the free-air carbon dioxide enrichment (FACE) experimental facility in northern China. The above-ground biomass and root biomass were significantly increased under elevated [CO2]. Elevated [CO2] significantly decreased the N concentration of the above-ground part at the beginning bloom (R1) stage, but had no effect at the beginning pod (R3), beginning seed (R5) or harvest stage. The concentration of ureide in the upper most fully-expanded leaf was not significantly affected by elevated [CO2] at any growth stage. Elevated [CO2] increased P concentration of the above-ground plant parts at the R1 and R5 stages, but did not affect P concentration at the R3 stage or at harvest. However, K concentration of the above-ground plant parts and root was not affected by elevated [CO2] at any growth stage. At harvest, elevated [CO2] significantly increased N, P and K uptake in soybean seed. Results indicate that more N, P and K fertilizers may be required to maintain the availability of these elements in the soil for soybean under future elevated [CO2] environments. 2015 Elsevier B.V. All rights reserved.

The expansion of canola production in Australia coincided with an increase in cropping intensity and a reduction in pastures and tillage. These changes mean that nitrogen (N) is often recognised as the most limiting nutrient in canola production, and is the largest single input cost for many growers. Canola responds to added N by producing larger plants that results in a longer leaf area duration, building a larger photosynthetic canopy for seed filling. Although the crop can compensate for poor early growth, a larger canopy is able to compete more effectively against weeds and helps reserve water for crop transpiration rather than soil evaporation. Nitrogen uptake is most rapid during stem elongation, and the N acquired can be remobilised to developing pods and then to seeds. Unlike wheat, N uptake can continue until drought or high temperatures prevent further assimilate supply to the reproductive apex. Data from Australian experiments that measured N uptake over the whole growth period showed that each tonne of seed required ~80 kg N to be taken up, and this forms the basis of a budgeting approach for determining N supply. Typically, added N reduces seed oil concentration at a rate of between –0.03 and –0.13%/kg N. Despite this decline due to added N, oil yield usually increases and the overall value of the crop also increases. Nitrogen has little impact on oil quality or seed glucosinate concentration. The efficiency and effectiveness of N management depends first on selecting a rate appropriate to the water-limited yield potential. Most growers estimate the N rate required using an N budget based on supplying 80 kg N/t less indigenous N supply. The budgeted N can be split over two, three or even more applications with little loss in agronomic efficiency. Splitting application enables growers to make decisions about N when there is more certainty about seasonal conditions. Urea is the most common N source used, and unless there are particular loss processes that are likely to occur, it is cheap and effective. Suggested areas for future N research on canola are to develop tools that can assess in-crop N status, an evaluation of late season N product rate and timing particularly on seed oil concentration, N management for grazed canola, and the development of guidelines to identify, and then address, particular N loss pathways using enhanced efficiency fertilisers.

Juncea canola (Brassica juncea L.) is being developed throughout the worlds canola growing countries as a drought tolerant, shatter resistant and highly blackleg resistant option to canola (Brassica napus L.). Juncea canola was grown commercially in Australia for the first time in 2007. This study determined the incidence and severity of blackleg infection in juncea canola prior to commercial release throughout south-eastern Australia in 2006 and 2007, and then again 5 years after commercialisation (2010–2013) to determine if blackleg severity had increased. Blackleg was found at all 127 sites surveyed throughout Victoria, New South Wales, South Australia and Western Australia. The severity of blackleg infection differed among sites and among the juncea canola cultivars and breeding lines suggesting that differences in resistance may be present. This is the first report that L. maculans isolates virulent on B. juncea are already widespread throughout the Australian canola growing regions and contradicts the widespread opinion that B. juncea is immune to blackleg. This also demonstrates that blackleg infection was already occurring in juncea canola prior to commercialisation of this crop in Australia and that disease management strategies similar to those used in canola cultivation will need to be implemented.

A reliable supply of high quality phosphorus (P) has been a cornerstone of agricultural development across the globe. In Australia P has been recognised as a key agricultural input since the founding work by Professor J.D. Custance at Roseworthy, South Australia in the 1880's. As most farmers and advisors now clearly recognise, P is an essential nutrient for successful crop and pasture growth that has no substitutes.

The High Rainfall Zone (HRZ) of southern Australia has high yield potential; however, current on-farm yields are often only half to a third of these values averaging 2.7 t ha-1 for wheat and 1.4 t ha-1 for canola. The unrealised potential appears to be due to low nutrient status. A range of data sets have been compiled to help identify the extent of nutrient deficiencies (N, P, K and S) in different HRZ regions. This information along with a current experimental program being conducted in the HRZ will help advance the biophysical modelling and economic analyses of nutrient use and help determine the levels of fertiliser required to boost wheat and canola profits on individual farms.

Australian grain production depends on applied fertiliser, particularly nitrogen (N) and phosphorus (P), and to a lesser extent potassium (K) and sulfur (S). Despite this dependence, soil testing is used sparingly as a tool to underpin fertiliser decisions. Some grain producers typically conduct soil tests at least once every 3 years on a selection of individual fields, but it is broadly understood that many grain producers use soil testing rarely or not at all. The choice by many grain producers not to support fertiliser decisions by soil testing relates to several factors. One key factor has been a perception that soil test interpretation criteria, previously published separately before collation by K. I. Peverill, L. A. Sparrow, and D. J. Reuter, may be biased or unreliable. The current paper provides an overview of research findings, presented in this special edition of Crop & Pasture Science, describing a national approach to the collation of all available and statistically valid N, P, K, and S response trials for cereal, oilseed, and pulse crops in Australia. It provides an overview of the process adopted to make this single national dataset available to both the grains and fertiliser industries. The process to build adoption has formed an integral component of the approach, as calibration data derived from the national database are being used to underpin soil test interpretation as part of fertiliser recommendations made through Fertcare to grain producers in Australia.

Under a future climate for south-eastern Australia there is the likelihood that the net effect of elevated CO2, (eCO2) lower growing-season rainfall and high temperature will increase haying-off thus limit production of rain-fed wheat crops. We used a modelling approach to assess the impact of an expected future climate on wheat growth across four cropping regions in Victoria. A wheat model, APSIM-Nwheat, was performance tested against three datasets: (i) a field experiment at Wagga Wagga, NSW; (ii) the Australian Grains Free Air Carbon dioxide Enrichment (AGFACE) experiment at Horsham, Victoria; and (iii) a broad-acre wheat crop survey in western Victoria. For down-scaled climate predictions for 2050, average rainfall during October, which coincides with crop flowering, decreased by 32, 29, 26, and 18% for the semiarid regions of the northern Mallee, the southern Mallee, Wimmera, and higher rainfall zone, (HRZ) in the Western District, respectively. Mean annual minimum and maximum temperature over the four regions increased by 1.9 and 2.2°C, respectively. A pair-wise comparison of the yield/anthesis biomass ratio across climate scenarios, used for assessing haying-off response, revealed that there was a 39, 49 and 47% increase in frequency of haying-off for the northern Mallee, southern Mallee and Wimmera, respectively, when crops were sown near the historically optimal time (1 June). This translated to a reduction in yield from 1.6 to 1.4 t/ha (northern Mallee), 2.5 to 2.2 t/ha (southern Mallee) and 3.7 to 3.6 t/ha (Wimmera) under a future climate. Sowing earlier (1 May) reduced the impact of a future climate on haying-off where decreases in yield/anthesis biomass ratio were 24, 28 and 23% for the respective regions. Heavy textured soils exacerbated the impact of a future climate on haying-off within the Wimmera. Within the HRZ of the Western District crops were not water limited during grain filling, so no evidence of haying-off existed where average crop yields increased by 5% under a future climate (6.4–6.7 t/ha). The simulated effect of eCO2 alone (FACE conditions) increased average yields from 18 to 38% for the semiarid regions but not in the HRZ and there was no evidence of haying-off. For a future climate, sowing earlier limited the impact of hotter, drier conditions by reducing pre-anthesis plant growth, grain set and resource depletion and shifted the grain-filling phase earlier, which reduced the impact of future drier conditions in spring. Overall, earlier sowing in a Mediterranean-type environment appears to be an important management strategy for maintaining wheat production in semiarid cropping regions into the future, although this has to be balanced with other agronomic considerations such as frost risk and weed control.

The oilseed industry in south-eastern Australia is based almost entirely upon canola, a situation that carries the risks of the breakdown of blackleg resistance or the incidence of other pests and diseases. Additionally, despite the rapid increase in area sown, canola is poorly adapted to drier areas such as the Mallee regions of Victoria and South Australia. Because of these reasons, there is a need to evaluate other oilseeds for suitability to south-eastern Australian farming systems, especially in light of the trend to more intensive cropping and the expansion into high rainfall areas. More crop options will give the changing farming systems greater bio-diversity and lead to enhanced sustainability. Additionally, a diverse range of oilseeds could provide market opportunities for non-food uses such as neutraceuticals or oleochemicals. This paper discusses a preliminary assessment of the agronomic potential some nontraditional oilseeds for production in south-eastern Australia.

Chapter 6 Plant Responses to Increased Carbon Dioxide S. Seneweera, S. Seneweera Department of Agriculture and Food Systems, Melbourne School of Land and Environment, The University of Melbourne, Private Bag 260, Horsham, Victoria 3400, AustraliaSearch for more papers by this authorR. M. Norton, R. M. Norton International Plant Nutrition Institute, 54 Florence St, Horsham, Victoria 3400, AustraliaSearch for more papers by this author S. Seneweera, S. Seneweera Department of Agriculture and Food Systems, Melbourne School of Land and Environment, The University of Melbourne, Private Bag 260, Horsham, Victoria 3400, AustraliaSearch for more papers by this authorR. M. Norton, R. M. Norton International Plant Nutrition Institute, 54 Florence St, Horsham, Victoria 3400, AustraliaSearch for more papers by this author Book Editor(s):Shyam S. Yadav PhD, Shyam S. Yadav PhD Agriculture—Capacity Development, Civilian Technical Assistance Program, General Directorate of Programs, Ministry of Agriculture, Irrigation & Livestock, Government of Islamic Republic of Afghanistan, Kabul, AfghanistanSearch for more papers by this authorRobert J. Redden PhD, Robert J. Redden PhD Australian Temperate Field Crops Collection, Grains Innovation Park, The Department of Primary Industries, Private Bag 260, Horsham, Victoria 3401, AustraliaSearch for more papers by this authorJerry L. Hatfield PhD, Jerry L. Hatfield PhD USDA-ARS National Laboratory for Agriculture and the Environment, 2110 University Blvd., Ames, IA 50011, United States of AmericaSearch for more papers by this authorHermann Lotze-Campen PhD, Hermann Lotze-Campen PhD Potsdam Institute for Climate Impact Research (PIK), P.O. Box 601203, 14412 Potsdam, GermanySearch for more papers by this authorAnthony E. Hall PhD, Anthony E. Hall PhD Department of Botany and Plant Sciences, University of California, Riverside, CA 92521-0124, United States of AmericaSearch for more papers by this author First published: 18 August 2011 https://doi.org/10.1002/9780470960929.ch15Citations: 13 AboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onFacebookTwitterLinked InRedditWechat Summary Rising atmospheric carbon dioxide (CO2) enhances carbon uptake in C3 plants and reduces stomatal conductance in C3 and C4 plants. Even though leaf N declines, RuBisCO activity increases so the photosynthetic rate rises as does photosynthetic N use efficiency. The responses show high variability, and while the magnitude of this "fertilization" effect appears to be confounded with experimental conditions. Growth of C3 plants increased by up to 25% and grain yield somewhat less. C3 plants are more responsive that C4 plants and legumes more responsive than grasses. Photosynthetic acclimation to high CO2 constrains the response of current genotypes. Improved understanding of plant N dynamics and fine and cause of RuBisCO coupled to balancing sink numbers is the basis of developing crops for a carbon rich future. To do so require screening of large numbers of genotypes under high [CO2] and then exploit those traits using modern biotechnology tools. This is to be done against the other abiotic challenges of drought and thermotolerance, as well as responding to a host of new biotic challenges thrown up by changing global climates. Citing Literature Crop Adaptation to Climate Change RelatedInformation

Blackleg (causal agents Leptosphaeria maculans and L. biglobosa) is the most significant disease of canola (Brassica napus) worldwide. This was the first survey of Leptosphaeria isolates recovered from Brassica juncea stubble in Australia. Sixty-four L. maculans isolates and 88 L.biglobosa 'canadensis' isolates were collected from B. juncea stubble over two years (2005-2006). These isolates were screened over three canola quality B. juncea and three B. napus differentials. As expected, L. biglobosa 'canadensis' isolates caused lower disease severity than the L. maculans isolates. However, 13 L. biglobosa 'canadensis' isolates were capable of causing epsilon 50% mean internal infection on at least one of the six differentials. Although these isolates were recovered from B. juncea stubble, disease severity was low when canola quality B. juncea differentials were inoculated. The same differential lines were also screened over two field sites by placing pots containing each of the differential lines onto B. napus and B.juncea stubble from commercial fields. At one site, inoculum in B. napus stubble caused higher internal infection severity than the B. juncea stubble in all differentials except B. napus differential 'ATR-Beacon'. At the other site, however, inoculum from B. juncea stubble produced more internal infection in one B. juncea differential in 2007 and in four differentials in 2008. This investigation suggests that when B.juncea is widely grown, increased blackleg symptoms could occur and that L. biglobosa 'canadensis' isolates can contribute to disease severity.

Blackleg disease severity of Brassica napus (canola) was reduced when canola plants were artificially inoculated with a non-aggressive Leptosphaeria biglobosa ‘canadensis’ isolate prior to inoculation with an aggressive L. maculans isolate. The reduction in blackleg severity by inoculating plants with a non-aggressive Leptosphaeria isolate consistently occurred for both B. napus and B. juncea cultivars. The only cultivars that were not protected were the susceptible control cvs. Karoo and Q2. Inoculation of plants with the L. biglobosa ‘canadensis’ isolate 48 hours after inoculation with the aggressive L. maculans isolate was less effective, with internal infection severity not significantly reduced compared to inoculation with just the L. maculans isolate alone. The use of L. biglobosa ‘canadensis’ as a biological control offers a potential management practice that could complement host resistance.