We study the throughput scaling of large-scale wideband sensory relay networks. Specifically, we consider a relay network model that consists of one source-destination pair and n relay nodes, where each relay node is power-constrained and the communication bandwidth is large. Assuming a relay traffic pattern, we investigate cooperative relaying across relay nodes, each using amplify-and-forward with channel estimation. We examine the scaling behavior of the corresponding achievable rates for the source-destination pair, in the asymptotic regime in terms of bandwidth W, the channel coherence interval L and the number of relay nodes n. Since energy efficiency is of paramount importance in sensor networks, we study two power allocation policies at relay nodes, namely a simple equal power allocation policy and the optimal power allocation policy. Our results indicate that these two strategies lead to the same throughput scaling, and the scaling law can be achieved by the equal power allocation policy under the same scaling-law-achieving conditions as by the optimal power allocation policy. We also investigate opportunistic relaying and threshold-based relaying and the corresponding achievable rates.