Novel Practices and Smart Technologies to Maximize the Nitrogen Fertilizer Value of Manure for Crop Production in Cold Humid Temperate Regions

Manure applications support crop production, maintain soil fertility, and recycle locally available nutrients in cold humid temperate regions, consistent with the principles of sustainable agriculture. Manure may be an excellent nitrogen (N) fertilizer for crops if it provides plant-available N as ammonium (NH4+) and from organic N mineralization in synchrony with crop N demands. The objective of this review was to describe the N fertilizer value of manure based on its physico-chemical characteristics, its transformation into plant-available N as modulated by soil abiotic and biotic conditions, and agronomic practices related to manure handling, storage, and land application. Methods of measuring the plant-available N released from manure and estimating its N fertilizer value are presented. Finally, we discuss how sensor networks can be used to optimize the N fertilizer value of manure. Our concept includes (1) a smart approach to conserve manure N in livestock production facilities and storages and (2) a smart system for precise spatio-temporal application of manure to deliver plant-available N in synchrony with crop N demands. Sensor networks that monitor real-time changes in ammonia (NH3) and oxygen concentrations should help to minimize losses of plant-available N during manure storage. On-the-go technologies for variable rate manure application will be linked with multispectral crop data and geospatial soil inputs to make a smart decision system that can maximize the N fertilizer value of manure in cold humid temperate regions.