Effects of starter nitrogen fertilizer on soybean root activity, leaf photosynthesis and grain yield.

The objective of this study was to examine the impact of starter nitrogen fertilizer on soybean root activity, leaf photosynthesis, grain yield and their relationship. To achieve this objective, field experiments were conducted in 2013 and 2014, using a randomized complete block design, with three replications. Nitrogen was applied at planting at rates of 0, 25, 50, and 75 kg N ha-1. In both years, starter nitrogen fertilizer benefited root activity, leaf photosynthesis, and consequently its yield. Statistically significant correlation was found among root activity, leaf photosynthetic rate, and grain yield at the developmental stage. The application of N25, N50, and N75 increased grain yield by 1.28%, 2.47%, and 1.58% in 2013 and by 0.62%, 2.77%, and 2.06% in 2014 compared to the N0 treatment. Maximum grain yield of 3238.91 kg ha-1 in 2013 and 3086.87 kg ha-1 in 2014 were recorded for N50 treatment. Grain yield was greater for 2013 than 2014, possibly due to more favorable environmental conditions. This research indicated that applying nitrogen as starter is necessary to increase soybean yield in Sangjiang River Plain in China

Monthly weather data for the 2013 and 2014 growing seasons.

<p>Monthly weather data for the 2013 and 2014 growing seasons.</p

Characteristics of the topsoil (0–20 cm) before the experiment.

<p>Characteristics of the topsoil (0–20 cm) before the experiment.</p

Effects of nitrogen treatments on dry root weight at different stages (g plant^-1).

<p>Effects of nitrogen treatments on dry root weight at different stages (g plant^-1).</p

Planting, herbicide application, plant sampling, harvest, and soil sampling dates, 2013–2014.

<p>Planting, herbicide application, plant sampling, harvest, and soil sampling dates, 2013–2014.</p

Effects of starter nitrogen fertilizer on N yield in leaf at different stages (g m^-2).

<p>Effects of starter nitrogen fertilizer on N yield in leaf at different stages (g m^-2).</p

Effects of starter nitrogen fertilizer on leaf area index at different stages.

<p>Effects of starter nitrogen fertilizer on leaf area index at different stages.</p

Effects of starter nitrogen fertilizer on leaf photosynthetic rate at different stages (μmol CO₂ m^-2 s^-1).

<p>Effects of starter nitrogen fertilizer on leaf photosynthetic rate at different stages (μmol CO₂ m^-2 s^-1).</p

Correlation coefficients among grain yield, root activity, dry root weight, leaf area index, specific leaf weight, photosynthetic rate, chlorophyll content and leaf N yield.

<p>Correlation coefficients among grain yield, root activity, dry root weight, leaf area index, specific leaf weight, photosynthetic rate, chlorophyll content and leaf N yield.</p

Effects of starter nitrogen fertilizer on leaf chlorophyll content at different stages.

<p>Effects of starter nitrogen fertilizer on leaf chlorophyll content at different stages.</p