Case Study 6

Case Study 6. Contrasting soil management strategies to improve soil quality while minimizing external input of P in potato crops. Atlantic Central (Belgium).

Which problem will be solved: Soil management strategies for organic cropping systems will be developed aiming at the sustainment of soil quality on one hand and a balanced P supply on the other hand.

State of the art: An increasing amount of easily available P, as a result of a high soil P status (most of the Flemish agricultural and horticultural land) seems to counteract microbial activity in the rhizosphere. In particular, organic growers rely on this microbial activity in the rhizosphere as a plant feeding mechanism. Therefore, soil management strategies should aim at preventing P surpluses by reducing external input of organic matter.

Objective: The objective is to explore to what extent innovative strategies, contributing to soil quality and N supplying capacity might reduce P surpluses compared to the usual soil management.

Proposed management practices: N:P and C:P ratios of farm yard manure (FYM) will be modified by co-composting FYM with ‘brown’ material (e.g., grass clippings from nature reserves). The effect of co-composted FYM, compared to stockpiled FYM, on crop performance and soil quality will be assessed in a 3-year field trial with repetitive application of both fertilization products. In the same trial, three different management variants will be applied for cover crop mixtures grown in between the main crops in the 3-year rotation. This will affect cover crop biomass development resulting in differences with regard to C and N input, and therefore possibly in differences with regard to main crop performance and soil quality.

Progress with the case study in relation with the state of the art: This case study will illustrate best practices for soil fertility building while minimizing P input or balancing P input by fertilization products with P export by harvested plant parts.

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