Evaluation Planty Organic 2012-2020: Plant-based fertilizer

Methodology

Situated on the SPNA experimental farm Kollumerwaard, from 2012 up to 2020 the Planty Organic experiment was run: an organic arable farming system based on 100% nitrogen input by means of leguminous plants. Soil, crops, green manures and Cut&Carry fertilizers were measured. In 2019 and 2020 six more fields were monitored from the Kollumerwaard organic business unit, the Kollumerwaard Conventional business unit and a nearby situated organic farm, thus enabling system comparisons. All data were used to create in total 12 field scenarios in the Ndicea App. In case of Planty Organic, KW Organic and KW Conventional the model scenarios were good enough to be transformed into Ndicea scenarios on rotation level. These three scenarios are used to compare results such as input-output, nitrogen losses, nitrogen use efficiency, organic matter dynamics and field-internal dynamics.

Results

Planty Organic has a high score in N-efficiency and environmental and biodiversity indicators. Productivity is substantially lower than in KW Conventional. The soil organic matter and the soil organic nitrogen levels are stable in the Planty Organic system. This is a remarkable result, considering the zero external input in this system. KW Organic has a middle position. The productivity is in the same order as in Planty Organic, but beside the arable products grassclover is taken out and manure is brought in. This can be considered as a partly internal flow, enabling animal production elsewhere. The nitrogen losses (leaching, denitrification, volatilization) are comparable to KW Conventional. KW Organic is the system in which a small but clear increase in soil organic matter is realized, mainly due to the use of solid goat manure.

Follow-up plans

It is proposed to continue the trial field, using regional residual streams as inputs to compensate for nutrient runoff with products, with P balance as a guideline. Strips will remain unfertilized to create sharp contrasts in soil P to enable research on P availability under low or no P supply.