Study of Improving Yield Prediction and Sulfur Deficiency Detection Using Optical Sensors.

In Maine, consistent yield of potatoes was 38 t ha^-1, but optimum weather improved it to 44 t ha^-1 in 2016 according to the New England Ag Statistics, which confirms that increasing the yield and quality of potatoes with current fertilization practices is difficult, hence; new or improvised agronomic methods are needed to meet with producers and industry requirements. Variable rate of inseason N application has a potential to achieve the geographical demands of a specific crop such as potato under a short growth window in Maine. Normalized difference vegetative index (NDVI) sensors have shown promises in regulating N as an inseason application; yet, using late N may stretch out the maturation stage. The purpose of the research was to test Trimble GreenSeeker^® (TGS) and Holland Scientific Crop Circle™ ACS-430 (HCCACS-430) wavebands, to predict potato yield, before the second hilling (6-8 leaf stage). Ammonium sulfate, S containing N fertilizer, not advised to apply on acidic soils but a accounts 60-70% fertilizer in Maine’s acidic soils, therefore, sensors used on sulfur deficient site to produce sensor-bound S application guidelines before recommending non-S-bearing N sources. Two study sites investigated for this research includes an S deficient site and a regular spot with two kinds of soils. Six N treatments, with both calcium ammonium nitrate and ammonium nitrate, under a randomized complete block design with four replications, were applied at planting. NDVI readings from both sensors were obtained at V8 leaf stages before the second hilling. Both sensors could predict N and S deficiencies with a strong interaction. However, HCCACS-430 was observed to be more virtuous than TGS. The correlation between NDVI (from both the sensors) and the potato yield improved using proprietor-proxy leaf area index (PPLAI) from HCCACS-430.

Keywords: NDVI, sensor, nitrogen, sulfur, leaf area index and weather