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Journal of Cleaner Production
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| Abstract: |
Producing safe food under excessive fertilization strategies is a serious issue; thus, this study introduced
a novel approach combining K-humate and calcium chloride under nitrogen (N) fertilization for maximizing potato (Solanum tuberosum L.) yield and improving quality by reducing nitrate (NO3 ) accumulation in tubers. A two-season field experiment during the 2017 and 2018 growing seasons was
conducted in a farm field with a sandy loam texture. The experiment followed a modified Box-Behnken
design with 13 treatments, which combined ammonium sulfate (N-AS), K-humate (KH) and calcium
chloride (CC) alternately using their maximum rates (370 kg N ha1 for Z, 8.0 kg kH ha1 for X, and
1.20 kg Ca ha1 for Y) and subdividing. A three-level, three-variable central composite model (TCCM),
integrated with regression modeling, was interpreted to illustrate the combined effects of AS, KH and CC
on all the variables under investigation. The results indicated a remarkable increment in tuber yield and
nitrate accumulation with the N-AS inputs, while KH and CC had minor impacts; however, the later
decreased the nitrate concentration to some extent. The maximum soil N content (25 mg kg1), tuber N
content (18 g kg1) and nitrate accumulation (450.5 mg kg1), which exceeds the acceptable limit
(200 mg kg1) for human consumption, was recorded under the application of 370 kg N ha1 as the
ammonium sulfate fertilizer with the conventional farming practices used. The response surface combined with regression models showed that the N rate (246 kg N ha1), when combined with KH
(1.33 kg ha1) and CC (0.2 kg ha1) representing T8 (66.6% N-AS þ 16.6% KH þ 16.6% CC), could reduce
the NO3 content in tubers to an acceptable level (170 mg kg1) and at the same time resulted in the
highest tuber yield (58.8 Mg ha1). The regression models accurately predicted the changes in nitrate
accumulation in tubers, soil N and plant attributes under different N rates as related to KH and CC.
Generally, when using these models under similar soil conditions worldwide, it can be concluded that
using 222, 2.5, and 0.2 kg ha1 of ammonium sulfate, potassium humate, and calcium chloride,
respectively, would achieve a proximal yield (56 Mg ha1) while simultaneously decreasing nitrate
accumulation in tubers to a very safe level (160 mg kg1).
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