Speaker
Description
- Introduction
Potato farmers are easily tempted to apply high N rates (Vos, 1999). This runs counter to an increasing interest in society to use nitrogen (N) fertiliser efficiently. The conventional fertiliser strategy for potatoes in The Netherlands is a single basal N application shortly before or after planting. Sidedress or split N application has been proposed as an alternative fertiliser strategy that can increase N use efficiency, either by increasing the yield while applying the same amount of N, or by maintaining yield while applying less N (van Evert et al., 2012).
Most experimental work on sidedress in potato has shown disappointing results, i.e. in most cases no yield gains at same N applied. Most scientific research on sidedress has been experimental, experimenting in 2-3 years, with just 1 or 2 soils and often with only one potato cultivar. The objective of the current research was to more systematically simulate possible yield gains or N saving from sidedress. - Materials and methods
We used a potato crop growth model Tipstar (Jansen, 2008) to simulate for 3 cultivars (early, normal and late maturing), on 2 soils (sandy/clayey) and 38 years of weather data for one location in the Netherlands. For each combination we made pair-wise comparisons: - SIDE vs SREC = Sidedress versus single recommended (high) N application – where we hypothesise that sidedressing maintains yields at lower total N applied;
- SIDE vs SMOD = Sidedress versus single moderate N application – comparing the two at similar total N applied - where we hypothesise that sidedressing increases yields at similar N applied but only in particular conditions: (a) late maturing cultivars, (b) sandy soils and (c) very wet 60 days period after planting.
- Results
Figure 1 presents the side-by side comparisons of SIDE vs SMOD at different total sidedress N applied by soil type and cultivar. On the clay soil (left column) orange dots show that at similar total N applied, yields are similar with single N and sidedress N, suggesting that on clay soils, little is to be gained from sidedress application. On the sandy soil (right column) green dots show that given a similar total N applied, yields are in most years similar and in a few years higher with sidedress. Closer analysis of model outcomes confirmed the two main hypotheses and revealed that at same total N applied (a) on sandy soils with wet spring sidedress reduces leaching and increases yield (b) sidedress offers greater benefits for late maturing cultivars in which N has more time to leach below the rooting zone and (c) sidedress offers greater benefits in years with high rainfall in the 60 days after planting, which a 16% probability of occurring in the past 38 years.
Figure 1. Comparing the sidedress fertiliser strategy with the Single Moderate fertiliser strategy (SIDE vs SMOD) in terms of yields and total N applied. Per soil x cultivar x Ntarget (TN) combination 38 dots from simulations in 38 years.
4. Discussion
These results give deeper insight in the underlying causes of when and when not sidedress offers advantages over the conventional single N application. Understanding these causes allows for generalisations to other crops and other conditions. Results suggest that possible benefits of sidedress are strongly dependent on weather, soil and cultivar. The results also show where crop growth models can play a valuable role in research: they allow for analysing crop fertiliser response in a great range of weather conditions which is particularly relevant when potential benefits of a particular fertiliser strategy (like sidedress) occur only rarely, in specific weather conditions like a very wet 60 days after planting.
5. References
Jansen, D.M., 2008. Beschrijving van TIPSTAR : hét simulatiemodel voor groei en productie van zetmeelaardappelen. Plant Research International. https://edepot.wur.nl/27135
van Evert, F.K., Booij, R., Jukema, J.N., ten Berge, H.F.M., Uenk, D., Meurs, E.J.J.B., van Geel, W.C.A., Wijnholds, K.H., Slabbekoorn, J.J.H., 2012. Using crop reflectance to determine sidedress N rate in potato saves N and maintains yield. Eur J Agron 43, 58-67 https://doi.org/10.1016/j.eja.2012.05.005
Vos, J., 1999. Split nitrogen application in potato: Effects on accumulation of nitrogen and dry matter in the crop and on the soil nitrogen budget. Journal of Agricultural Science 133, 263-274. https://doi.org/10.1017/S0021859699006966
| Keywords | Sidedress nitrogen; split nitrogen; nitrogen fertiliser; Crop growth model; Tipstar |
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