Chlorophyll meter – a decision-making tool for nitrogen application in wheat under light soils

Abstract

<span>Nitrogen (N) in plants is generally diagnosed by a soil test and plant tissue analysis.<br /><span>However, such analyses are costly in terms of time and money and are not easily accessible by<br /><span>researchers and extension workers, let alone farmers. Alternative cost-effective methods are<br /><span>required for rapid analysis of the N status of crops and to guide N management in wheat. The<br /><span>objective of this study was to assess whether the SPAD values using a leaf chlorophyll meter<br /><span>could be used to apply N at the maximum tillering (MT) stage of irrigated spring wheat grown<br /><span>under light soils of South Asia. Experiments were conducted over two years under light soils at<br /><span>the Wheat Research Centre (WRC), Dinajpur, Bangladesh. Treatments were 80, 100 and 120<br /><span>kg N ha<span>−1<span>, applied two-thirds as basal and one-third at the crown root initiation (CRI) stage<br /><span>along with additional 10, 20 and 30 kg N ha<span>−1 <span>(first year) and 0, 10, 20 and 30 kg N ha<span>-1 <span>(second<br /><span>year) at MT. Rates at MT were determined on the basis of SPAD values, which fell below the<br /><span>critical value of 37.5, recorded at 45 days after sowing (DAS). SPAD values recorded at 55 and<br /><span>65 DAS were positively correlated with grain yield (GY), indicating that the application of extra<br /><span>N at MT influences wheat GY. Our results have two major implications: (i) SPAD values based<br /><span>on a leaf chlorophyll meter can be used for N application and (ii) extra 30 kg N ha<span>-1 <span>at MT is<br /><span>recommended for achieving maximum GY of irrigated spring wheat under the light soils of<br /><span>South Asia.</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span><br /><br class="Apple-interchange-newline" /></span></span></span></span></span></span></span></span></span>