HIGHLIGHTS:
Humic acid and nitrogen doses have a positive influence on nitrogen and organic matter concentration in alkaline soil.
Humic acid and nitrogen doses improve nitrogen concentration in corn plants.
Humic acid and nitrogen doses increase corn growth and yield.
ABSTRACT
Humic acid (HA), as a bio-stimulant and a major component of organic matter (OM), can improve plant physiology, soil fertility, and nutrient availability, mainly in low OM soils. Nitrogen (N) is one of the most important nutrients that affect several metabolic and biochemical activities, leading to improved plant development. This study was conducted to investigate the combined effect of HA and N doses on soil organic matter (SOM) and total N concentration, N uptake, corn growth, and grain yield under conventional tillage at Peshawar, Pakistan. Treatments were tested in a randomized block design with four replicates arranged in a factorial scheme 3 × 4 + 1. The respective doses of HA (1.5, 3,0 and 4.5 kg ha-1) were applied at the corn sowing, whereas N doses (80, 120, 160, and 200 kg ha-1) were applied in three splits (1/3 at sowing, 1/3 at the V5 stage, and remaining 1/3 at the tasselling stage) with one control (no HA and N). The application of HA, regardless of the applied doses, had positive effects on SOM, N concentration, N uptake, corn development, and grain yield. However, the application of 4.5 kg ha-1 of HA was the most effective in promoting SOM (0.83%) and total N (0.31%), shoot biomass (10610 kg ha-1), N uptake (1.13%), and grain yield (3780 kg ha-1), even when combined with the N doses of 80, 120 and 160 kg N ha-1. Increasing N doses positively influenced SOM, N concentration, N uptake, and corn growth. The greatest grain yield was obtained at 150 kg ha-1 of N regardless of HA applied doses.
Key words:
Zea mays L.; grain protein; organic fertilizer; nitrogen fertilization
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Different letters correspond to a significant difference at p ≤ 0.05 by Tukey test; *, ** and ns - Significant at p ≤ 0.01 and p ≤ 0.05, and not significant by F test, respectively
Different letters correspond to a significant difference at p ≤ 0.05 by Tukey test; *, ** and ns - Significant at p ≤ 0.01 and p ≤ 0.05, and not significant by F test, respectively
STRN - Straw N concentration; GRN - Grain N concentration; GRPROT - Grain protein concentration; PH - Plant height; SOM - Soil organic matte; SOILN - Soil total N; BIOM - Shoot biomass; HI - Harvest index and YIELD - Grain yield