Direct Screening of Micronutrients on Maize Plant Leaves Using Handheld X-ray Fluorescence Spectrometer (HHXRF)

Abstract

Foliar nutrient analysis is an indication of soil’s elemental compositions. However, its use has been limited by the short window available for plant sampling and analysis since different plant species utilize nutrients differently. With the emergence of quick, non-destructive, inexpensive, and portable-spectral techniques like handheld X-ray Fluorescence spectrometer (HHXRF), the merits of foliar analysis can be explored and utilized. Analysis can be carried out both in the laboratory or in-situ set up. In this study, maize leaves sampled at two growth stages were collected in Muguga Kenya. And were analyzed in three different sample matrices, i.e. green (fresh), oven dry, and milled (powder). Na, K, Ca, Cu Fe, Mg, Mn, Mo, Zn, S and P nutrients were studied using Handheld X-ray Fluorescence (HHXRF) spectrometer to assess its applicability. Milled samples gave higher concentrations for the elements: Na; 43.8mgkg, Mg; 3077.1mg/Kg, P; 1741.4mg/Kg, S; 1878.5mg/Kg, K; 37988.8mg/Kg and Ca; 5294.7mg/Kg; as compared to concentrations in oven-dried samples that gave Na; 10.54 mg/kg, Mg; 956.01 mg/Kg, P; 802.07 mg/Kg, S; 1055.53 mg/Kg, K; 20550.35mg/Kg and Ca; 3224.11mg/Kg; however, there was no significant difference between oven dry and milled samples (P > 0.05). Fresh samples recorded the lowest concentrations and milled samples presented the highest correlation (r2> 0.95). A relation between nutrient concentrations with seasonal variations showed higher nutrient concentrations for P; 1038mgkg-1 ±174mgkg-1, K; 22994mgKg-1 and Calcium at early growth stage compared to tussling stage where the concentration were 791mg/kg-1 and 20409.37mgKg-1 for P and K respectively. Nutrient content showed inconsistency depending on specific element and plant part; K, S, P exhibited decreasing nutrient concentration from the leaf base; for example a concentration of 5630.16 mg kg-1 and 2457.79 mg kg-1 for Sulphur at leave base and apex respectively; on the other hand increase in concentration from leaf base to the apex were observed in Na,Fe,Mn and Zn; Iron had a concentration of 298.03 mg kg -1, 315.14 mg kg -1 and 423.59 mg kg -1 at base ,middle part and apex respectively. Copper and Molybdenum was found to be uniformly distributed along leaf. However, it is necessary to carry out additional studies between elemental concentration in the soil and their respective content in plants. There is need to test applicability of the technique on different crops and sample matrix.