Effects of Nitrogen Application on Root Length and Grain Yield of Rain‐Fed Maize under Different Soil Types

Abstract

The effect of fertilizer N on maize (Zea mays L.) root size has been reported with inconsistency. It remains unclear whether a quantitative relationship exists between soil NO3–N and root growth under field conditions. A 3‐yr field experiment was conducted in three soils (loamy clay, clay loam, and sandy loam) with five N treatments (from 0–312 kg N ha−1). Soil NO3–N concentration and total root length were determined to a depth of 60 cm at the silking stage. It was found that plants grown in clay loam soil had larger root size compared with the other two soil. A weak parabolic relationship between N supply and root length was found in loamy clay and clay loam soil, but not in sandy loam soil. There was a parabolic relationship between soil NO3–N concentration in the 0‐ to 60‐cm depth and total root length per plant. This relationship was mostly found in clay loam soil. Across soils and years, there was a parabolic relationship between root length density (RLD) and shoot dry matter (DM) at silking and between RLD at silking and grain yield with fertilizer N rate £240 kg N ha−1. It is suggested that it may be not practical to regulate total root length by simply adjusting N fertilizer amount. Total root length is not relevant to maize yield under excess N input conditions.Core Ideas Plants grown in clay loam soil had larger root than in loamy clay and sandy loam soils. A parabolic relationship between soil nitrate‐N concentration and total root length. A weak parabola relationship between N supply and root length was found in loamy clay soil and clay loam soil, but not in sandy loam soil. Root length and the maximum yield reached synchronously at optimum N rates (168–240 kg N ha−1 in the present study).

Peer Review #1 of "Shoot and root traits of summer maize hybrid varieties with higher grain yields and higher nitrogen use efficiency at low nitrogen application rates (v0.1)"

“…Nitrogen application has a positive effect on root growth (Liu et al, 2009;York et al, 2015) but also adverse effects when provided in excess (Tian et al, 2008;Chen et al, 2015). Root growth has a parabolic linear relationship with the nitrogen application rate and excessive nitrogen application limits the growth of the root system (Feng et al, 2016). Our results are similar to those obtained in previous studies.…”

“…The effects of various factors mean that roots respond to nitrogen in significantly different manners in field trials compared with culture experiments (Wang et al, 2003;Tian et al, 2005). The effects of nitrogen application on the roots are inconsistent under field conditions, where some studies suggest that nitrogen application can promote root growth, whereas others indicate that it can inhibit the growth of the root system (Chen et al, 2015;Feng et al, 2016). There are reports showing that several plant shoot traits could also be associated with grain yield and NUE in selecting for improving grain yield under low nitrogen conditions (Banziger & Lafitte, 1997;Haegele et al, 2013;Chen et al, 2016;Talabi et al, 2017), such as leaf longevity (stay-green), anthesis-silking interval, leaf chlorophyll concentration, grain N accumulation and also number of kernels per ear.…”

Genotypic Differences in Root System Size in White Mustard in Relation to Biomass Yield and Soil Nitrogen Content

“…A stronger correlation was found for root system parameters in the 0.5 -1 m layer, where Brassicaceae catch crops in particular showed higher root density than cereals. Thorup-Kristensen and Rasmussen (2015) observed similar results, when the relationship between root system growth and nitrogen uptake of catch crops was found in soil profile layers lower than 1 m. However, higher root density did not always lead to an increase in N consumption (Wendling et al, 2016;Feng et al, 2016;Herrera et al, 2010). When comparing old and modern wheat varieties, Aziz et al (2016) discovered that the RLD and total length of the root system decreased with ongoing breeding processes, but the efficiency of N uptake increased.…”

Field phenotyping of plant roots by electrical capacitance – a standardized methodological protocol for application in plant breeding: a Review

“…A larger root system is considered to be an advantage, especially in the absence of sufficient water and nutrients, in a less fertile environment and in organic farming (Comas et al, 2013;Svačina et al, 2014), for enabling a more effective use of the nutrients from the soil, and thus lowering the contamination of the environment with unused nutrients, especially nitrogen and phosphorus (Gewin, 2010;Klimek-Kopyra and Rębilas, 2018). However, a higher root density did not always lead to an increase in nitrogen consumption (Wendling et al, 2016;Feng et al, 2016;Herrera et al, 2010). When comparing old and modern wheat varieties, Aziz et al (2017) discovered that the root length density and total length of the root system decreased with ongoing breeding processes, but the efficiency of nitrogen uptake increased.…”