Radiation efficiency and nitrogen fertilizer impacts on sunflower crop in contrasting environments of Punjab, Pakistan

Jabran, Khawar/0000-0001-8512-3330; Rehmani, M.I.A./0000-0001-7922-1233; Rahman, Muhammad Habib ur/0000-0002-2823-9959; Amin, Asad/0000-0003-2242-8377; Ahmad, Ashfaq/0000-0002-9249-185X; Turan, Veysel/0000-0001-7805-8411; Shah, Ghulam Mustafa/0000-0003-1230-7029 WOS: 000419944100076 PubMed: 29103112 Sunflower (Helianthus annuus L.) is the leading non-conventional oilseed crop in Pakistan. Nitrogen fertilizer can affect plant growth and productivity by changing canopy size which has an effect on the radiation use efficiency (RUE) of the crop. The response of sunflower hybrids in terms of phenology, fraction of intercepted radiation (F-i), and RUE to nitrogenous rates (0, 60, 120, 180, and 240 kg ha(-1)) was studied in three field experiments conducted in three various environments: Multan (arid), Faisalabad (semi-arid), and Gujranwala (sub-humid) during spring seasons 2008 and 2009. The treatments were laid out according to a randomized complete block design with split plot arrangements, keeping the sunflower hybrids in main plots and nitrogen rates in subplots, and replicated three times. The results showed Hysun-38 took a maximum number of days to anthesis (101) as compared to Pioneer-64A93 (100) and Hysun-33 (99). The mean values of F-i were 0.850, 0.903, and 0.978, and the estimated values of RUE for total aboveground dry matter were 2.14, 2.47, and 2.65 g MJ(-1) at experimental locations of Multan, Faisalabad, and Gujranwala, respectively. The values of RUE for grain yield (RUEGY) were 0.78, 0.98, and 1.26 g MJ(-1) at experimental locations of Multan, Faisalabad, and Gujranwala, respectively. The average RUEGY values over three locations were 2.61, 2.60, 2.43, and 2.36 g MJ(-2) in N-4 (180 kg ha(-1)), N-5 (240 kg ha(-1)), N-3 (120 kg ha(-1)), and N-2 (60 kg ha-1) treatments, respectively. Increasing rates of N increased RUEGY over the standard treatment N-3 (120 kg N ha(-1)); however, the averaged values over three locations were 1.22, 1.08, 0.99, and 0.92 g MJ(-2) in N-4, N-5, N-3, and N-2 treatments, respectively. Therefore, optimum water and N doses are important for attaining higher RUE, which may enhance sunflower growth and yield. Pakistan Science Foundation (PSF); University of Agriculture, Faisalabad, Pakistan The first author is highly thankful to the Pakistan Science Foundation (PSF) for the partial funding to present this work in a second International Balkan Agriculture Congress at the Namik Kemal University, Tekirdag, Turkey (2017). Moreover, the first author is also appreciative to the Endowment Fund Secretariat, University of Agriculture, Faisalabad, Pakistan, which was highly acknowledged for the partial financial support of this study.