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.