Predicting the effect of rotation design on N, P, K balances on organic farms using the NDICEA model

Abstract

The dynamic model Nitrogen Dynamics in Crop rotations in Ecological Agriculture (NDICEA) was used to assess the nitrogen (N), phosphorus (P) and potassium (K) balance of long-term organic cropping trials and typical organic crop rotations on a range of soil types and rainfall zones in the UK. The measurements of soil N taken at each of the organic trial sites were also used to assess the performance of NDICEA. The modeled outputs compared well to recorded soil N levels, with relatively small error margins. NDICEA therefore seems to be a useful tool for UK organic farmers. The modeling of typical organic rotations has shown that positive N balances can be achieved, although negative N balances can occur under high rainfall conditions and on lighter soil types as a result of leaching. The analysis and modeling also showed that some organic cropping systems rely on imported sources of P and K to maintain an adequate balance and large deficits of both nutrients are apparent in stockless systems. Although the K deficits could be addressed through the buffering capacity of minerals, the amount available for crop uptake will depend on the type and amount of minerals present, current cropping and fertilization practices and the climatic environment. A P deficit represents a more fundamental problem for the maintenance of crop yields and the organic sector currently relies on mined sources of P which represents a fundamental conflict with the International Federation of Organic Agriculture Movements organic principles.

Assessing the multidimensional elements of sustainability in European agroforestry systems

“…A pluriannual study could provide an improved assessment of nutrient-use efficiency in AF systems. The deficits of phosphorus across the case study sites are also in-line with previous assessments of agroecological systems and could be partly addressed by sewage sludge application, although this would require a change in international organic standards on the certified farms (Smith et al 2016).…”

“…Comparing all three datasets (scores, raw indicator value and Pearson's correlation-based assessments) reveals potential negative trade-offs within the case studies from a nutrient management perspective; conflicting with generic claims that agroecological systems can foster improvements in soil quality (Reganold and Wachter, 2016), most of the systems assessed faced considerable surpluses or deficits with regard to N and/or P and K. The N surplus on most of the sites is in-line with a recent meta-analysis of nutrient budgets for agroecological farming systems (Reimer et al 2020). This surplus could relate to poor synchronicity between N supply and demand in lowinput systems relying on biological N fixation (the AF case studies in UK, DK and PL relied heavily on N fixation through clover and lucerne leys) as this can make the efficient supply and utilisation of N more difficult than a system relying on readily available N sources through manufactured fertiliser (Smith et al, 2016). Low crop yields in the year of the assessment could have also contributed, as 2017-2018 was a particularly dry and warm year, particularly southern / south-eastern parts of Europe (C3S, 2021).…”

Simulating cropping sequences using earth observation data

“…Indeed, many studies focus on choosing the optimal crop rotation to maximise one or more chosen outputs. For example, Smith et al (2016) looked at the effect of changing the rotation design on soil N, P, and K balances. In many studies, it is common to rely on "typical rotations" for use in the baseline scenarios as Smith et al (2016) did in their study on soil nutrients.…”

“…For example, Smith et al (2016) looked at the effect of changing the rotation design on soil N, P, and K balances. In many studies, it is common to rely on "typical rotations" for use in the baseline scenarios as Smith et al (2016) did in their study on soil nutrients. Alternatively, a model system is chosen, and data on the cropping history from a typical study site or region is used as the baseline for simulations (e.g.…”

The greenhouse gas impacts of converting food production in England and Wales to organic methods

“…Could yields under organic management be improved to reduce land requirements? Improvements in organic rotation design and more effective and reliable supplies of N from biological fixation are possibilities 38,39 . However, these improvements are probably marginal, given the fundamental requirement for more leys in rotations under organic management.…”