Influence of varying tillage systems and nitrogen application on crop allometry, chlorophyll contents, biomass production and net returns of maize (Zea mays L.)

•Subsoil compaction due to conventional tillage is a serious problem for maize production.•Deep tillage coupled with nitrogen application improved maize production.•Chiseling improved crop allometry, and resulted 23% more grain yield than other tillage systems.•Nitrogen application at the rate of 200 kg ha−1 recorded 21% and 8% higher grain and dry matter yield of maize.•Nitrogen application at the rate of 200 kg ha−1 along with chiseling improved the economics of maize production.

Subsoil compaction and injudicious use of nitrogenous fertilizers are key factors for lowering maize yield. Maize yield can be improved by minimizing subsoil compaction through deep ploughing, and using required amount of nitrogen fertilizer. Therefore, this two-year field experiment was conducted to evaluate the effects of varying tillage systems and nitrogen application on leaf chlorophyll contents, allometric traits, grain yield and net returns of maize (Zea mays L.). The study consisted of i) three tillage systems viz. conventional tillage (using cultivator), deep tillage with moldboard plough + 2-cultivations, and deep tillage with chisel plough + 2-cultivations; and ii) three nitrogen levels viz. 100, 150 and 200 kg ha−1. Tillage systems and nitrogen levels improved allometric traits, grain and dry matter yield, and net returns of maize in both years. Chisel tilled plots observed more leaf area index and duration, and crop growth rate which ultimately resulted in 23 and 8% more grain and dry matter yield, respectively compared with moldboard tilled plots. Similarly, nitrogen application at 200 kg ha−1 recorded higher leaf area index and duration, crop growth rate, chlorophyll contents, and 21% and 8% higher grain and dry matter yield respectively, compared with control. Maximum net return and benefit-cost ratio was recorded from maize grown under chisel ploughed plots by applying 200 kg ha−1 nitrogen. Therefore, maize should be grown with 200 kg ha−1 nitrogen application by preparing the field with chisel plough followed by cultivator to obtain higher grain yield and net returns under semi-arid conditions of Pakistan.