Potato (Solanum tuberosum L.) is a N intensive crop, and meeting its requirements with N fertilization is the primary practice to improve N recovery and achieve suitable tuber yield. A 3-site-year (SY) study was conducted to assess soil plant analysis development (SPAD)-502 chlorophyll meter efficacy for providing potato leaf real-time N status to adjust N timing and rate using nitrogen sufficiency index (NSI) thresholds of 90 or 95%. We evaluated effects of in-season SPAD-based N managements, as well as a reference with non-limiting N application, a fixed-timing (planting and hilling) conventional N fertilization, and a zero-N control on crop N uptake, tuber yield, and N-use efficiency of potato cultivar Agata grown in tropical clay soils. Tuber yields were similar in both SPAD-based managements. Under no intensive rainfall events after N applications, SPAD-based managements reduced N applications by 38–63% and resulted in comparable tuber set, bulking, and yield relative to conventional N fertilization. Additionally, SPAD-based management at a NSI threshold of 90% resulted in greater potato N-uptake efficiency and tuber yield per unit of N applied. SPAD-502 sensor was efficient for detecting plant N status when environmental conditions were more conducive for potato production and optimized N management by reducing application rates. However, with less favorable temperature and solar radiation for potato cultivation, and with intensive rainfall events following N application, SPAD readings did not guide to a proper N fertilization and resulted in reduced tuber yield. Therefore, under such conditions, a more accurate method for detecting plant N status should be used.
Bibliographical noteFunding Information:
We thank the Coordination for the Improvement of Higher Education Personnel (CAPES) for providing a scholarship to the first author (finance code 001), the São Paulo Research Foundation (FAPESP) for partially supporting this research (grant no. 2016/15396‐5), the National Council for Scientific and Technological Development (CNPq) for partially supporting this research and for granting awards for excellence in research to the second (grant no. 304736/2018‐0) and third authors. We are thankful to the potato grower (Ivan Fornaziero), who provided the area for this investigation (SYs 2 and 3) and the Brazilian Association of Potato (ABBA) who provided the seed tubers.
© 2021 The Authors. Agronomy Journal © 2021 American Society of Agronomy
Copyright 2021 Elsevier B.V., All rights reserved.