Abstract
In Maine, potato yield is consistent, 38 t·ha−1, for last 10 years except 2016 (44 t·ha−1) 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. Normalized difference vegetative index (NDVI) sensors have shown promise in regulating N as an in season application; however, 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, is not advised to be applied on acidic soils but accounts for 60–70% fertilizer in Maine’s acidic soils; therefore, sensors are 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 include 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 (8 leaf per plant) before the second hilling. Both sensors predict N and S deficiencies with a strong interaction with an average coefficient of correlation (r2) ~45. However, HCCACS-430 was observed to be more virtuous than TGS. The correlation between NDVI (from both sensors) and the potato yield improved using proprietor-proxy leaf area index (PPLAI) from HCCACS-430, e.g., r2 value of TGS at Easton site improve from 48 to 60. Weather data affected marketable potato yield (MPY) significantly from south to north in Maine, especially precipitation variations that could be employed in the N recommendations at planting and in season application. This case study addresses a substantial need to revise potato N recommendations at planting and develop possible in season N recommendation using ground based active optical (GBAO) sensors.
Highlights
Management of nitrogen (N) in potatoes is a well-established challenge not entirely owing to yield dependence and because of quality
The soil test analysis is a standard resource for growers to determine N recommendations but, since those recommendations came from ARF and significant difference in ARF and farmer site was recorded with respect to S
marketable potato yield (MPY) before second row-hilling and very close to first row-hilling (Figure 2), which created a potential for ground based active optical (GBAO) sensor to recommend N rate depending on maximum yield potential from that field and variety when there are several commercial potato varieties grown in the area, and each variety has different maximum yield potential
Summary
Increasing input cost on fertilizers (Figure 1) has made it Sensors 2017, 17, 1095; doi:10.3390/s17051095 www.mdpi.com/journal/sensors. Management of nitrogen (N) in potatoes is a well-established challenge not entirely owing to yield dependence and because of quality. Increasing input cost on fertilizers (Figure 1) has made impractical for for producers to gain a competent revenue with a with persistent potato price (Figure which1), is it impractical producers to gain a competent revenue a persistent potato price1),. (Figure further indicated by the decreasing number of farms in Maine [1]. Use of three major macronutrients, which is further indicated by the decreasing number of farms in Maine [1].
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