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Synthetic aperture radar (SAR) is more sensitive to the dielectric properties and structure of the targets and less affected by weather conditions than optical sensors, making it more capable of detecting changes induced by management practices in agricultural fields. In this study, the capability of C-band SAR data for detecting crop seeding and harvest events was explored. The study was conducted for the 2019 growing season in Temiskaming Shores, an agricultural area in Northern Ontario, Canada. Time-series SAR data acquired by Sentinel-1 constellation with the interferometric wide (IW) mode with dual polarizations in VV (vertical transmit and vertical receive) and VH (vertical transmit and horizontal receive) were obtained. interferometric SAR (InSAR) processing was conducted to derive coherence between each pair of SAR images acquired consecutively in time throughout the year. Crop seeding and harvest dates were determined by analyzing the time-series InSAR coherence and SAR backscattering. Variation of SAR backscattering coefficients, particularly the VH polarization, revealed seasonal crop growth patterns. The change in InSAR coherence can be linked to change of surface structure induced by seeding or harvest operations. Using a set of physically based rules, a simple algorithm was developed to determine crop seeding and harvest dates, with an accuracy of 85% (n = 67) for seeding-date identification and 56% (n = 77) for harvest-date identification. The extra challenge in harvest detection could be attributed to the impacts of weather conditions, such as rain and its effects on soil moisture and crop dielectric properties during the harvest season. Other factors such as post-harvest residue removal and field ploughing could also complicate the identification of harvest event. Overall, given its mechanism to acquire images with InSAR capability at 12-day revisiting cycle with a single satellite for most part of the Earth, the Sentinel-1 constellation provides a great data source for detecting crop field management activities through coherent or incoherent change detection techniques. It is anticipated that this method could perform even better at a shorter six-day revisiting cycle with both satellites for Sentinel-1. With the successful launch (2019) of the Canadian RADARSAT Constellation Mission (RCM) with its tri-satellite system and four polarizations, we are likely to see improved system reliability and monitoring efficiency.

Wheat (Triticum aestivum L.) yield is relatively low in eastern Canada. This study aimed to assess fertilizer N management options to improve the regional yield of wheat using the CSM- CERES-Wheat model. The model was adapted to simulate winter wheat by replacing air temperatures wiThestimated temperatures under snow cover, and then the model was evaluated for simulating winter wheat using experimental data collected at two sites and spring wheat at three sites in eastern Canada. Across all the experimental years and sites, the normalized root mean squared error (nRMSE) between simulated and measured yields was 14%. Regional yield under rainfed conditions in the Eastern Ontario Region (a Census of Agriculture unit as a case study) was simulated wiTh0, 1, 1.5, and 2 times the recommended N rate (around 50 kg N ha-1) and unlimited N for the calibrated cultivars of spring wheat from 1981 to 1999. The simulated average regional yield (in dry matter) wiThthe recommended N rate ranged from 2180 kg ha-1 for cultivar Hoffman to 2502 kg ha-1 for AC Brio. BoThwere close to the reported yield of 2440 kg ha-1, wiThnRMSE values ranging between 20.3 and 16.6%. The simulated regional yields wiThunlimited N were two times that wiThthe recommended N rate, showing a considerable yield gap. Our simulations indicate that regional yield could increase to 3600 kg ha-1 in the Eastern Ontario Region if the N rate was increased to around 100 kg N ha-1, although a slight decrease in N use efficiency would occur. In addition, wiThsuch increases in the N fertilization rate, other abiotic factors such as lodging should be evaluated. [ABSTRACT FROM AUTHOR]