Abstract
Fertilizer recommendations are key for farmers: the investment is relatively large for smallholders and risky with unknown yield responses and variable fertilizer prices. Are agronomists able to provide useful site-specific fertilizer recommendations that reduce these uncertainties? We evaluated the influence of errors introduced due to soil sampling and chemical analysis procedures both within- and among laboratories on fertilizer recommendations. Using what we consider to be conservative estimates of the uncertainty in estimating soil supply of N, P and K in a single composite soil sample, the resulting 90% confidence interval of fertilizer recommendations ranged from 86 to 186, 0–58 and 38–114 kg N, P and K ha−1 respectively. The numerous laboratory services and digital applications providing field-specific recommendations appear to promise more accuracy than soil analysis can realistically deliver. We conclude that a field-specific fertilizer recommendation based on a single composite soil sample is indeed a pipe-dream.
Highlights
Economic and environmental sustainability is key for future food systems
The parameters required by QUEFTS for this component are measured values for soil pH, soil organic carbon (SOC), available P based on Olsen (0.5 M NaHCO3, pH 8.5) extraction and exchangeable K based on a 1 M ammonium acetate extraction
We conclude that site-specific fertilizer recommendations based on a single soil sample is a holy grail that will remain elusive – a pipe-dream! Errors due from soil sampling and analysis methods result in inaccurate estimates of soil nutrient supply, yet these are needed to tailor fertilizer recommendations to individual fields
Summary
One of the most important aspects of sustainability of farming systems is the efficient use of nutrients. Ensuring efficient recovery of applied nutrients by crops makes optimal use of scarce resources, while preventing losses from the soil and damage to the environment. Maximum recovery efficiency can be achieved by optimizing amounts of inputs and timing of nutrient applications to plant demand, taking into account nutrient supply from the soil: the ultimate goal of the agronomist. In many smallholder farming systems soil P and K supply is limited, causing large spatial variability in crop yields (Njoroge et al, 2017, 2019). Soil fertility is strongly affected by past management of crop residue and application of animal manure (Giller et al, 2011), often preferentially applied on more intensively managed homefields or gardens (Tittonell et al, 2007)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
