Uptake kinetics of micronutrients in fennel (Foeniculum vulgare Mill.) with N input

Abstract

Study of nutrients uptake kinetics in crop plants is very important to determine the need of nutrients during crop growing period at a specific time, which relies upon a wide variety of factors, like plant species and their varieties, environmental conditions, soil properties, nutrients supply and soil microorganism etc. Therefore, to study the uptake kinetics of micronutrients, field experiments were carried out on sandy loam soil of Typic Haplustepts with six N levels i.e. 0, 40, 60, 80, 100 and 120 kg ha-1 and compared with absolute control. Uptake of micronutrients and their uptake rate was calculated at 11-60, 61-90, 91-120 and 121-180 day interval. Result revealed that the uptake of iron, zinc, manganese and copper increased with increased levels of applied nitrogen and advancing age of crop plants. It was highest at 120 kg N ha-1 during 121-180 days after sowing (DAS). Uptake of Fe and Mn was exponential while Cu was linear up to 180 days, whereas Zn made plateau beyond 120 DAS of the crop. Uptake rate of Fe and Cu showed linear pattern with increasing levels of N (upto 120 N kg ha-1) at all the four stages of the crop. However, uptake rate of Mn and Zn was different with rates of N application and was nearer to the linear trend up to 91-120 DAS. Fe uptake rate was remarkably higher during 121-180 DAS over the 91-120 DAS with all the levels of applied N. Uptake rate of Mn drastically reduced during 121-180 DAS than 91-120 DAS with all the levels of N. Hence, it can be concluded that application of N have positive response for uptake and uptake rate of micronutrients in fennel irrespective of growth stages, while uptake rate of Mn and Zn varied with stageswhereas the uptake rate of Fe and Cu continued, or even increased after plant senescence appeared, reflects that Zn and Mn are more responsible for growth of areal parts of fennel and Fe and Cu for root growth. Hence later stage application of Zn and Mn may be discouraged, while Cu and Fe application may continue for higher yield, nutrients use efficiency andratooning. Whereas, Mn and Zn uptake rate reduced with senescence of crop. This is because of fennel is an ‘Herbaceous perennial bushy’ plant and root remains active even beyond the senescence of aerial part of crop.