Humic acid and nitrogen dose application in corn crop under alkaline soil conditions

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.

摘要 腐殖酸（Humic acid, HA）作为一种生物刺激素与有机质（organic matter, OM）的核心组分，可改善植物生理状态、提升土壤肥力与养分有效性，在低有机质土壤中效果尤为显著。氮素（N）是影响植物多项代谢与生化活动的关键养分之一，可促进植物生长发育。本研究于巴基斯坦白沙瓦地区的常规耕作条件下开展，旨在探究腐殖酸与氮肥配施对土壤有机质（soil organic matter, SOM）、全氮含量、氮素吸收、玉米生长及籽粒产量的综合影响。试验采用随机区组设计，设置3×4+1因子方案，共4次重复。其中腐殖酸施用量设3个水平（1.5、3.0、4.5 kg·ha⁻¹），于玉米播种时施用；氮肥施用量设4个水平（80、120、160、200 kg·ha⁻¹），分三次施用：播种时施入总量的1/3，V5生长期施入1/3，剩余1/3于抽雄期施入，另设置不施加腐殖酸与氮肥的空白对照处理。无论腐殖酸施用量如何，其施用均对土壤有机质、全氮含量、氮素吸收、玉米生长及籽粒产量产生正向促进作用。其中，4.5 kg·ha⁻¹的腐殖酸施用量效果最优，可使土壤有机质含量达到0.83%、全氮含量达到0.31%，地上部生物量达10610 kg·ha⁻¹，氮素吸收提升1.13%，籽粒产量达3780 kg·ha⁻¹，且该效果在与80、120、160 kg·ha⁻¹的氮肥配施时依然显著。随着氮肥施用量的增加，土壤有机质、全氮含量、氮素吸收及玉米生长均呈正向响应。无论腐殖酸施用量如何，氮肥施用量为150 kg·ha⁻¹时均可获得最高籽粒产量。