Comparison of the effect of different methods and levels of irrigation and fertilization on the yield and morphophysiological characteristics of fodder maize

Improper management of irrigation and fertilizing methods cause large amounts of chemical fertilizers to be removed from the reach of plants and enter water sources through leaching.

The research was conducted in the Research Farm of the Campus of Agriculture and Natural Resources of Razi University. The experiment was carried out in two crop years (2020-2021) and factorial in the randomized complete block design with three replicates. Experimental treatments included four levels of irrigation (wick irrigation, furrow irrigation with 50, 70, and 100% of the plant's water requirement) and two levels of nitrogen fertilizer (50 and 100% of the recommended fertilizer through urea). In the wick irrigation method, fertilizer was provided to the plant through tanks and in solution. While in the furrow irrigation method, fertilizer was used as topdressing. The amount of urea fertilizer required for each treatment was calculated based on the soil test. CROPWAT 8.0 program and Penman-Monteith method were used to calculate the volume of water consumption and potential evapotranspiration (ETo). The studied traits included number of nodes, internode length, number of yellow leaves, number of green leaves, total number of leaves, plant height, ear height, stem diameter, leaf area, leaf area index, specific leaf weight, fresh fodder yield, dry fodder yield, water consumption, the relationship between water consumption and fresh fodder yield, and the relationship between water consumption and dry fodder yield. Data were compared using LSD test at the 5% probability level.

The results of variance analysis showed that the number of yellow leaves, ear height, leaf area index, leaf area, specific leaf weight, fresh forage yield, and dry forage yield were affected by year, fertilizer, and irrigation treatments. The interaction effect of fertilizer and irrigation on the total number of leaves, stem diameter, and plant height was significant. The mean comparison showed that wick irrigation with 100% fertilizer consumption had the highest stem diameter and plant height at the 5% probability level. In each year, there was a slight difference between the treatments in terms of ‎dry fodder yield. In the first year, wick irrigation with 100% fertilizer had ‎higher dry fodder yield compared to furrow irrigation with 50% water ‎consumption and 50 or 100% fertilizer consumption and wick irrigation with 50% ‎fertilizer consumption. In the second year, wick irrigation with 100% ‎fertilizer consumption was superior to furrow irrigation with 70% water ‎consumption and 100% fertilizer consumption and furrow irrigation with 50% ‎water and 50% fertilizer consumption. In the first year, furrow irrigation with 100% water consumption and 100% fertilizer and wick irrigation with 100% fertilizer had more leaf area index than other treatments. The water consumption in the wick irrigation method was less than that of the furrow irrigation with 70% of the plant's water requirement. The reduction of water consumption in the wick method can be due to the reduction of the wet surface of the soil, which reduces evaporation, because this irrigation method spreads water on a limited surface.

In total, wick irrigation with 50% fertilizer consumption was recommended as the best treatment due to the saving in water (58%) and fertilizer. Although wick irrigation has a higher cost than furrow irrigation, but due to the dry climate of Iran and the high value of water, this irrigation method is useful.