Zinc fertilization of lentil in Saskatchewan to increase yield and grain zinc content

Abstract

Zinc (Zn) fertilization is considered an important agronomic strategy for global food security. Lentil production in Saskatchewan not only provides significant economic benefit for growers, but is marketed in several countries where human Zn deficiencies are common. The impact of Zn fertilization on lentil yield and Zn concentration deserves attention. Field experiments were conducted in 2013 to determine if Zn fertilization of lentil could increase yield, grain Zn concentration and its bioavailability for humans in three popular lentil cultivars: CDC Maxim (red), CDC Imvincible (small green) and CDC Impower (large green). The effects of three rates (0, 2.5 and 5 kg Zn ha-1) of soil applied ZnSO4 were examined at a site in the Brown soil zone identified as Zn deficient and a site in the Dark Brown soil zone that was identified as sufficient in soil Zn. In 2014, hard red spring wheat was seeded to assess the residual effects on a rotational crop. A companion pot study was conducted in a polyhouse that compared single rates of soil and foliar applied forms of Zn fertilizer: soil applied ZnSO4, foliar applied Zn lignosulphonate, soil and foliar applied Zn chelated with EDTA. At the two field sites, soil applied ZnSO4 fertilizer had no significant effect on lentil yield, grain Zn concentration, and predicted bioavailability of Zn for humans. Significant differences in residual DTPA-extractable Zn were generally not found among rates of applied ZnSO4 fertilizer, and soil applied ZnSO4 did not have residual benefits for spring wheat grown at either location in 2014. Migration of Zn into less labile soil fractions was identified as a factor contributing to this general lack of response to soil applied ZnSO4 fertilizer. Based on results from the polyhouse study, chelated forms of Zn may be more effective than inorganic or organic-complexed forms of Zn in supplying Zn and improving predicted dietary bioavailability of lentils for humans. Phytate:Zn molar ratios were significantly decreased in all lentil cultivars fertilized with soil applied Zn that was chelated with EDTA (17.1) compared to when fertilized with soil applied ZnSO4 (24.7). Overall, the responses of lentil to Zn fertilization were small and variable, such that significant economic benefits were not observed.