Map-based site-specific seeding of seed potatoes by fusion of proximal and remote sensing data

Uniform rate seeding (URS) is not the optimal approach to utilize the yield potential of different zones of a field. This study examines the potential of map-based site-specific seeding (SSS) of seed potatoes for improving crop yield and economic return. A field (6 ha) was scanned using an on-line visible and near-infrared (vis-NIR) spectroscopy and electromagnetic induction (EMI) sensors. The k-means clustering was used to divide this field into management zones (MZ) using two data sets i.e., apparent electrical conductivity (EMI-MZ), and data fusion of two normalized differential vegetation indexes (NDVIs) retrieved from Sentinel2 images with on-line vis-NIR measured soil pH, organic carbon, available P, K, Mg, Na and moisture content (visNIRSen-MZ). Seed potatoes (Solanum tuberosum L. cv. Hermes) were planted at 11, 13, 15, 17 and 19 cm spacing intervals by sowing more seeds to the fertile zones and vice versa. Yield analysis demonstrated that SSS increased overall yield (EMI-MZ: 32.42 Mg ha-1, visNIRsen-MZ: 31.89 Mg ha-1), compared to URS (31.06 Mg ha-1). Although visNIRSen-MZ had a lower gross yield than EMI-MZ, the increased yield of small size (28-45 mm) tubers, having higher market price than other size categories has resulted in an actual market price for the former larger than that of the latter approach. Economic analysis revealed that SSS resulted in a higher gross margin than the URS, whilst both the MZs approaches performed almost equally. The visNIRsen and EMI produced a gross margin of 4995 € ha-1 and 4947 € ha-1, respectively while URS's gross margin was 4528 € ha-1. In contrast to URS, visNIRsen-MZ and EMI-MZ increased gross margin by 467 € ha-1 and 419 € ha-1, respectively. The visNIRsen-MZ approach saved seeding costs by 14 € ha-1 although EMI-MZ consumed 5 € ha-1 more compared to URS. Therefore, it is recommended to adopt SSS in seed potato, as a means of increasing crop yield, reducing input cost, and thus maximizing profitability compared to URS