The Long Term Nutrient Depletion Project (LTNDT, Danish: Udpiningsmarken)

Depletion trial field

History and background

Testing the impact on crops, soil or the environment from application of nitrogen (N), phosphorus (P) or potassium (K) in mineral or orgacinic fertilisers, generally requires an experimental site low in available nutrient. However, many arable soils in Denmark are high in available P and K due to generous fertilisation with inorganic fertilisers and animal manures for decades.

At the University of Copenhagen the Long-term Nutrient Depletion Trial was established back in 1964, at the time when Danish agriculture began to use synthetic mineral fertilizers at commercial sclae. Professors at the Department of Plant Nutrition, KVL, decided that this field of 8.5 ha sandy clay loam soil should not receive any P or K containing fertilizers or manures, like it was recommended common agricultural fields at the time. Only moderate amounts of mineral nitrogen fertiliser to maintain some cereal crop yield, to test how this would deplete the soil of available nutrients. Thirty years later, soil available P and K levels had decreased to very low values (Olsen-P of 11 mg kg-1 and exchangeable K of 55 mg kg-1) due to crop removals and soil depletion.

Therefore, in 1996 a new experimental design was applied in the majority of the field, with more varied crop rotations and seven nutrient application treatments, including both mineral fertilisers and animal manure, giving different combinations of the three macronutrients (N, P, K). The overall objective of the new experimental design was to study how soil biology, physics, chemistry and crop physiological response and yield for different crop species and cultivars react when an arable soil low in P and K receives variable combinations of N, P and/or K in mineral fertilizers or animal manures.

From 2010, we decided to split up the treatments to further diversify into 14 different N, P and K combinations in both mineral fertiliser, manure and combinations.  The experiment is laid out as a block design experiment with four replications of all 14 treatments.

This means the area has treatments (without P and K) that are almost 60 years old and very depleted  (often more than 50% yield reduction), while other treatments over the last 25 years have been fertilized to more normal levels or even treatments with a surplus and thus increasing soil analysis values.  Therefore, the experimental area is very unique, there is only one other similar experiment in Denmark, at Askov Research Station under AU, and only a handful of similar ones in the whole world.

 

The LTNDT is a so-called workshop area within in the university farms, which means the basic agronomic maintenance of the field is covered by the university, but any trial sampling, harvest or analysis requires external funding. This has been done from various sources, such as on-going projects with activities in subplots of the trial:

  • MiCroP (IFD-financieret, 2014-2017)
  • Soil Biological Fertility – Sustainability of Organic and Inorganic Fertilization Practices (Internt KU bonus PhD, 2014-2017)
  • FutureCropping (IFD-financieret, 2015-2019)
  • NutHY (Org-RDD, 2017-2021)
  • CatCap (Klimaforskningsprogrammet for Landbrug, 2019-2023)
  • INTERACT (NNF CCRP projekt, 2019-2024)

Many ag-bio-tech companies, including NovoZymes Bioag and Chr. Hansen, has several times utilised soil or plant samples from the trial in their commercial innovation activities on plant biologicals.

Data are available for crop biomass production, yield and nutrient uptake for most years.

We are very open to collaboration on the use of the trials, as long as the permanent long-term treatments are not altered or additional nutrients applied. Please direct any enquiries on collaboration or access to soils or samples to Lars Stoumann Jensen, (lsj@plen.ku.dk)

 

 

The large number of related studies accomodated within the trial as described above, has resulted in a number of outcomes. For example, the relationship of root hair promoted P uptake of selected barley genotypes to the grain yields in P limiting soil (Gahoonia and Nielsen, 2004), or the ability of different catch crop species to mobilise and take up P and K from soils of low availability, as well as their ability to deliver P and K to the subsequent main crop (Jensen et al., 2005; Hansen et al., 2023). Others have studied how biobased fertiliser function on differently depleted soils (Gomez et al., 2022; 2023), and the impact of fertiliser treatments on the seed and rhizosphere microbiome (van der Bom et al., 2018; Hansen et al., 2020; Nunes et al 2023). Finally van der Bom et al., (2017, 2019a, b) studied the fundamental impacts of the long-term NPK treatments on crop yields and soil P dynamics.

Gahoonia, T. S., Nielsen, N. E.. 2004 Barley genotypes with long root hairs sustain high grain yields in low-P field. Plant and Soil. 262, 55-62. https://doi.org/10.1023/B:PLSO.0000037020.58002.ac

Jensen LS, Pedersen A, Magid J, Nielsen NE. 2005 Catch crops have little effect on P and K availability of depleted soils. DARCOF e-news 2, 1-7.

van der Bom F., Magid J., Jensen L.S. (2017) Long-term P and K fertilisation strategies and balances affect soil availability indices, crop yield depression risk and N use efficiency. European Journal of Agronomy 86, 12–23 http://dx.doi.org/10.1016/j.eja.2017.02.006 

van der Bom, F.J.T., Nunes, I., Raymond, N.S., Hansen, V., Bonnichsen, L., Magid, J., Nybroe, O., Jensen, L.S. (2018) Long-term fertilisation form, level and duration affect the diversity, structure and functioning of soil microbial communities in the field. Soil Biology & Biochemistry 122, 91–103. https://doi.org/10.1016/j.soilbio.2018.04.003

van der Bom F, Magid J., Jensen L.S. (2019a) Long-term fertilisation strategies and form affect nutrient budgets and soil test values, soil carbon retention and crop yield resilience. Plant and Soil 434, 47–64 https://doi.org/10.1007/s11104-018-3754-y

van der Bom F.J.T., T.I. McLaren, A.L. Doolette, J. Magid, A. Oberson, E. Frossard, L.S. Jensen (2019b) Influence of long-term phosphorus fertilisation history on the availability and chemical nature of soil phosphorus. Geoderma, 355, 113909 https://doi.org/10.1016/j.geoderma.2019.113909

Hansen V., Bonnichsen L., Nunes I., Sexlinger K., Lopez S. R., van der Bom F., Nybroe O., Nicolaisen M.H., Jensen L.S. (2020) Seed inoculation with Penicillium bilaiae and Bacillus simplex affects the nutrient status of winter wheat. Biology and Fertility of Soils, 56, 97–109, https://doi.org/10.1007/s00374-019-01401-7

Nunes I., Hansen V., Bonnichsen L., SU J., Hao X., Bak F., Raymond N.S., Nicolaisen M.S., Jensen L.S., Nybroe O. (2022) Succession of the wheat seed-associated microbiome as affected by soil fertility level and introduction of Penicillium and Bacillus inoculants in the field. FEMS Microbiology Ecology, fiac028, https://doi.org/10.1093/femsec/fiac028

Gómez-Muñoz, B., Müller-Stöver D., Hansen, V., Jensen, L.S., and Magid, J. (2022) Nutrient interactions and salinity effects on plant uptake of phosphorus from waste-based fertilisers. Geoderma 422, 115939 https://doi.org/10.1016/j.geoderma.2022.115939

Hansen V., Meilvang L.V., Magid J., Thorup-Kristensen K. and Jensen L.S. (2023) The effect of soil fertility on biomass production, nutrient uptake and fertilizing value of cover crops. European Journal of Agronomy 145 126796 https://doi.org/10.1016/j.eja.2023.126796

Gómez-Muñoz B., Magid J., Jensen L.S. (2023) Nitrogen, potassium and sulphur availability from residue-based fertilisers produced in Denmark applied singly or combined Geoderma Regional 33, e00650. https://doi.org/10.1016/j.geodrs.2023.e00650

 

Contact

Professor of Soil Fertility and Waste Recycling
Lars Stoumann Jensen
lsj@plen.ku.dk