Precision nitrogen-management practices influences growth and yield of wheat (Triticum aestivum) under conservation agriculture

A field experiment was conducted at New Delhi during the winter (rabi) season of 2012–13, to study the precision nitrogen management in wheat [Triticum aestivum (L.) emend. Fiori & Paol.] grown under conservation agriculture. The experiment was laid out in a factorial randomized-block design with 20 treatments combinations of four nutrient management in preceding maize (Zea mays L.) [absolute control, recommended dose of fertilizers (RDF), 50% RDF and site-specific nutrient management (SSNM)] and 5 precision nitrogen-management practices in wheat [control, RDF, green seeker, SPAD and soil-test crop response (STCR)]. Among the tested technologies for precision N management; a saving of N by 9.5 and 30 kg with green seeker and SPAD, respectively, while enhancement of 18.4 kg N/ha by STCR was found compared with RDF. The STCR-based nutrient-management plots received very less potassium (5.6 kg/ha) than RDF (40 kg/ha). The wheat growth parameters, viz. plant height, dry-matter accumulation, leaf-area index (LAI), tillers, crop-growth rate (CGR), relative growth rate (RGR) and net assimilation rate (NAR) were significantly higher by STCR-based nutrient management as well as with nutrient expert-based SSNM applied in maize as residual effect. The yield attributes, viz. effective tillers/m², grains/spike, harvest index and 1, 000-grain weight, were also recorded significantly higher with STCR and SSNM. However, the grain yield was 5% higher with STCR compared to RDF which was on a par with green seeker-based N management. Thus, the RDF in wheat needs to be revisited in western Indo Gangetic plains (IGP) as it responded to higher N levels and lower K application and green seeker sensor can be used for real time N management of wheat in this region while SSNM found best for maize.