IPN00003 - Nutrient Performance Indicators
The efficiency of nitrogen (N), phosphorus (P), potassium (K) and sulphur (S) use in the grains industry, as well as all agricultural production, using consistent and transparent methods was estimated. Regional and national balances show annual, spatial and industry variation. When considered across all sectors, P removal is significantly less than P supplied, while K and S application are significantly less than the amount of K and S removed in products. Nitrogen supplied, including fixed N, is generally less than N removed. Data collected from 500 farm paddocks over four or five years were similar and it is proposed that existing tools be used through farming systems groups to build a reference set for growers to benchmark nutrient efficiency.
The N-partial nutrient balance (PNB), P-PNB and K-PNB were estimated as 1.02, 0.44 and 1.8, respectively, for grain production in Australia. The N-partial factor productivity (PFP), P-PFP and K-PFP values were 52kg grain/kg N, 128kg grain/kg N and 724kg grain/kg K. The N-nutrient balance intensity (NBI), P-NBI and K-NBI values were +4.6kg N/ha, +7.2kg P/ha and -5.7kg K/ha. Compared to other countries, Australia generally has modest N imbalances using the assumptions implicit in the current literature. The P balances are generally positive (removal
If growers are to be encouraged to investigate performance indicators, reference methods reported should all follow the same protocols, preferably through a web-based calculator. There are important aspects of developing the methods to estimate indicators. These include validation of the biological nitrogen fixation (BNF) calculations, particularly for green and brown manure crops or pastures, verification of the nutrient concentrations in products removed, including crop residues, nutrient inputs from manures considered where appropriate, and nutrient losses from residue removal or burning are considered.
On-line calculators could be based on an on-line nutrient balance calculator (http://brasil.ipni.net/article/BRS-3293) developed by the International Plant Nutrition Institute (IPNI) Brazil that is being adapted to other regions. Alternatively, GRDC may consider adapting the Lime and Nutrient Balance calculator to a web-based platform. Irrespective of the tool selected, it should use regional grain nutrient concentrations and validated BNF estimates to derive PNB, NBI or PFP to be reported back to growers.
Defining the success of a nutrient management research project solely on the basis of the efficiency measured due to intervention is not likely to lead to positive outcomes overall. Certainly getting improved comparative efficiency, such as among different nutrient sources, or with different timings or through alternative placement strategies, are all valid ways to make comparisons, particularly when done at the same rate. There is no absolute number that can be used to define an acceptable efficiency, as the different loss processes have different impacts. For example, where a recovery efficiency (RE) or PNB are less than one, the nutrient that is unaccounted for may be entering lower available nutrient pools and/or contributing to increased soil test levels. Alternatively, where soil nutrient status is high, a high RE or PNB (i.e. higher than 1) may be desirable to target, while if nutrient status is low, a high PNB would be mining the soil resource.
Metrics, like PNB and agronomic efficiency (AE), do not provide any intelligence about the fate of the nutrients not taken up and removed by the crop. These metrics are not environmental indicators and a low or high PNB or AE is not necessarily good or bad. Losses may or may not be detrimental environmentally, and residual nutrient values may be significant. The recovery and productivity of nutrient inputs are better suited to long term studies of three to five years rather than single year responses.
If there is a desire to maintain an ongoing review of the performance of nutrients for the Australian grains industry, good quality production data are available at national, state and natural resources management (NRM) level through the Australian Bureau of Statistics (ABS) data collection services. Nutrient concentrations for Australian produce are known although this requires on-going verification and monitoring, particularly of regional values. In combination, the removal of nutrients can be reasonably estimated at a national and a state level but the precision is diminished when downscaled to regional (e.g. NRM) level. GRDC may consider working more closely with Fertilizer Australia, ABS and the Australian Bureau of Agricultural and Resource Economics (ABARE) to develop reliable good quality farm scale data. Additional paddock surveys present an excellent opportunity to capture some of these data, but the grains industry does not exist in isolation from other agricultural industries and nutrient inputs for pastures used for grazing livestock are likely to have residual value into grain production activities.
Nutrients represent a major investment for grain growers and monitoring their efficient and effective use represents an important aspect of long and short term management. In addition, inefficient use of nutrients can represent both an economic and environmental loss. There is international interest in monitoring nutrient performance through a range of metrics, including PNB (removal to use ratio), PFP and NBI. No individual metric provides a complete assessment of nutrient performance, and linkages to soil health and economic returns are also required.
This research established a series of protocols for collecting data to derive nutrient performance indicators that growers can use to reflect on the efficiency and effectiveness of their nutrient management strategies.
Because of the importance of fertiliser use economically and environmentally, there is increasing interest in developing ways to evaluate the efficiency and effectiveness of their use on farms. While there are many metrics that can be used as nutrient performance indicators (NPI), three in particular have become widely quoted. They are PNB, the quotient of nutrient removed in product and nutrient supplied to the crop, PFP, the quotient of grain and nutrient supplied to the crop and NBI, which is the amount of nutrient in deficit or surplus per hectare.
The nutrient performance indicators PNB, PFP and NBI are useful in assessing system performance. They are not indicators of environmental fate. These metrics can be applied at a range of scales from fields, to farms, to regions, to countries. It is critical to ensure that the data being used are transparent, auditable, referenced, consider all nutrient sources, are regionally relevant and appropriate to the intention as to how the metrics are to be interpreted. When taken alone, the numerical value of these indicators is of limited value, and they need to be considered over time and in concert with other measures. They are not environmental or economic indicators in their own right and interpreting them as such is inappropriate. The indicator values calculated need to be linked to other indicators such as yield and soil test values to gain an appreciation of their significance.
Norton et al. (2014) estimated the N-PNB, P-PNB and K-PNB as 1.02, 0.44 and 1.8, respectively, for grain production in Australia. The N-PFP, P-PFP and K-PFP values were 52kg grain/kg N, 128kg grain/kg N and 724kg grain/kg K. The N-NBI, P-NBI and K-NBI values were +4.6kg N/ha, +7.2kgP/ha and -5.7kg K/ha. Overall, Australia has modest N imbalances using the assumptions implicit in the current literature, compared to other countries. P balances are generally positive (removal
Development of an on-line nutrient balance calculator for growers to estimate PNB, PFP and NBI at a field level.
Develop and publish regional nutrient concentrations of grain and crop residues.
Current data derived from grower surveys is not individually identified to protect the confidentiality of the information provided by individual growers. There have been no commercialisation activities, but IPNI is proceeding to adapt the Brazilian calculator to a broader geography. The protection and sharing of any IPNI intellectual property (IP) can be discussed as that project proceeds.
A paper has been submitted to the International Nitrogen Conference for December 2016 (see Attachment 2).
1. Nutrient performance indicators scoping study.
2. Conference paper.
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