Salamanca-Jimenez Alveiro, Doane Timothy A, Horwath William R
Land Air and Water Resources Department, University of California, DavisDavis, CA, USA; National Center for Coffee Research, CenicaféManizales, Colombia.
Land Air and Water Resources Department, University of California, Davis Davis, CA, USA.
Front Plant Sci. 2017 Mar 2;8:223. doi: 10.3389/fpls.2017.00223. eCollection 2017.
Nitrogen (N) is the most limiting nutrient for coffee production in Colombia. An adequate supply is especially important during the vegetative period of growth, since any deficiency during this short period is known to have lasting effects on subsequent coffee bean production. Urea fertilizer is commonly applied on the soil surface since steep slopes hamper incorporation into soil, a practice which increases the risk of N volatilization. Little information is available on N recovery during early growth stages under different fertilizer application practices. The aim of this study was therefore to provide a comparison of N uptake during the early vegetative growth stage under surface-applied and incorporation practices at two contrasting locations. The highest proportion of plant N derived from fertilizer (Ndff) occurred 60 days following application at the site with greater precipitation and soil organic matter, where surface application also increased the Ndff in roots and stems after 120 days. Although fertilizer N supplied approximately 20-29% of total plant N after 4 months, this fertilizer-derived N corresponded on average to only 5% of the total application, indicating that very little fertilizer (relative to how much is applied) reaches plants during this time. Apart from the difference in Ndff observed at the wetter site, there was no effect of application method on dry weight and macronutrient content in different plant components, root to shoot ratio, and leaf C content. However, site effects were registered for most of these measurements, with the exception of total nutrient uptake. Similarly to Ndff trends, lower root/shoot ratio and higher concentrations of N, K, and Mg in aboveground biomass were found in the site with higher rainfall and soil organic matter, likely resulting from higher soil water and N availability. These findings provide new information useful as a direction for further research looking toward increasing NUE during the vegetative stage in Colombian coffee crops.
氮（N）是哥伦比亚咖啡生产中最具限制性的养分。在营养生长阶段，充足的供应尤为重要，因为在这一短暂时期内的任何养分缺乏都会对后续咖啡豆产量产生持久影响。由于陡坡阻碍了肥料混入土壤，尿素肥料通常施用于土壤表面，这种做法增加了氮挥发的风险。关于不同施肥方式下咖啡早期生长阶段氮素回收率的信息很少。因此，本研究的目的是比较在两个不同地点进行地表施肥和混入施肥时，营养生长早期的氮吸收情况。在降水量和土壤有机质较高的地点，施肥后60天，来自肥料的植物氮比例（Ndff）最高，120天后，地表施肥也增加了根和茎中的Ndff。尽管4个月后肥料氮供应了植物总氮的约20%-29%，但这种来自肥料的氮平均仅占总施用量的5%，这表明在此期间到达植物的肥料（相对于施用量而言）非常少。除了在较湿润地点观察到的Ndff差异外，施肥方式对不同植物组分的干重、大量养分含量、根冠比和叶片碳含量没有影响。然而，除总养分吸收外，这些测量中的大多数都存在地点效应。与Ndff趋势相似，在降雨和土壤有机质较高的地点，地上生物量中的根冠比更低，氮、钾和镁的浓度更高，这可能是由于土壤水分和氮素有效性较高所致。这些发现为进一步研究提高哥伦比亚咖啡作物营养生长阶段的氮利用效率提供了新的有用信息。
