Contents lists available at ScienceDirect Field Crops Research journal homepage: www.elsevier.com/locate/fcr Planting density and sowing date strongly influence growth and lint yield of cotton crops Aziz Khan a , Ullah Najeeb b , Leishan Wang a , Daniel Kean Yuen Tan b , Guozheng Yang a, ⁎ , Fazal Munsif c , Saif Ali a , Abdul Hafeez a a MOA Key Laboratory of Crop Eco-physiology and Farming System in the Middle Reaches of the Yangtze River, Huazhong Agricultural University, Wuhan, 43007, PR China b Faculty of Science, Plant Breeding Institute, Sydney Institute of Agriculture, School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia c Department of Agronomy, Amir Muhammad Khan Campus Mardan, The University of Agriculture, Peshawar, Khyber Pakhtunkhwa, 23200, Pakistan ARTICLE INFO Keywords: Cotton lint yield Sowing date Planting density Photosynthesis Nitrogen partitioning Assimilation ABSTRACT This study assesses the effects of plant population density (PPD) and sowing date (SD) on growth, physiology and lint yield of a cotton crop. Seedling transplanting is one of the most dominant cotton production systems in China. But on the other hand, the net benefit is decreasing because the system is labor intensive. Therefore, a shorter cotton growing season is urgently needed to reduce the production costs through management practices such as adjusting sowing date and PPD. The following hypothesis was tested; would cotton yield and physiology from a late sowing be compensated by plant density? Field experiments were conducted with two sowing dates (S 1 , May 20; S 2 , June 04) as the main plot and three PPDs (D 1, low; 7.5 × 10 4 ;D 2, moderate; 9.0 × 10 4 and D 3, high; 10.5 × 10 4 ha -1 ) as the sub-plot. Early-sown plants produced 23%, 32%, 55%, 77% and 14%, taller stems more nodes, leaves and fruits, respectively, than the late-sown plants. Consequently, S 1 produced 26% higher lint yield than S 2 . This increase in lint yield was mainly attributed to a relatively longer cropping season, which allowed utilization of available resources. Growth and fruit production in S1 plants were further increased by an increased photosynthetic rate (Pn) and N acquisition. Across the plant densities, 13% and 6% more lint yield was achieved under D 2 than the D 3 and D 1 , respectively. Moderate PPD increased lint yield by 13% and 6% over high and low, respectively. Nitrogen (N) acquisition was 45%, 33%, higher for S 1 sown crop compared with S 2 , respectively. S 1 D 2 had higher average (3.5 V T kg ha -1 d -1 ) and maximum (4.5 V M kg ha -1 d -1 ) rates of N accumulation in reproductive organs at the fastest accumulation point among other treatments. Our data suggest that for both sowing dates moderate PPD is a promising option, which allows light interception and penetration to the lower canopy, efficient N utilization and assimilate distribution to reproductive structures. 1. Introduction Cotton (Gossypium hirustum L.) is grown globally as a major source of natural fiber (Constable and Bange, 2015). Due its indeterminate growth habit, the crop shows morphological adaptations to its growing environment such as modification in canopy structure in response to sowing date (SD) and plant population density (PPD) (Mao et al., 2014; Zhang et al., 2003). These morphological adaptations in terms of canopy development, light interception, source sink relationship and assimilates partitioning are the major determinant of lint yield and quality (Yang et al., 2014a,b). Hubei is one of the major cotton growing provinces in China, contributing 12.3% of the total national lint production in less than 9.4% of the planting area (Yang and Zhou, 2010a,b). Despite introduction of high yielding varieties, cotton yield per unit area in this region is stagnant for the last decade (Yang et al., 2014a,b). Cotton planting is a laborious practice in this region due to raised bed sowing and transplantation into open field (Lu et al., 2017). This situation will worsen due to an accelerated migration of farm labor towards cities since1990 (Zhou, 2004). Therefore crop management techniques such as late sowing and high plant population density are often practiced to overcome input costs without sacrificing yield. With the introduction of row planting (Briggs et al., 1967), the concept of http://dx.doi.org/10.1016/j.fcr.2017.04.019 Received 16 March 2017; Received in revised form 28 April 2017; Accepted 29 April 2017 ⁎ Corresponding author. E-mail address: ygzh9999@mail.hzau.edu.cn (G. Yang). Abbreviation: PPD, plant population density; SD, sowing date; Pn, net photosynthetic rate; AVG, aminoethoxyvinylglycine; FB/FN, fruiting branch to fruiting node ration; RH%, percent relative humidity; FAP, fastest accumulation point; VT, average rate; VM, maximum rate; t 1 ,t 2 beginning and terminating days of the fast accumulation period; CNP, cotton plant nitrogen VON vegetative organ nitrogen; ROP, reproductive organ nitrogen; DAE, days after emergence Field Crops Research 209 (2017) 129–135 0378-4290/ © 2017 Elsevier B.V. All rights reserved. MARK