Yingchun Han

Light spatial distribution in the canopy and crop development in cotton.

The partitioning of light is very difficult to assess, especially in discontinuous or irregular canopies. The aim of the present study was to analyze the spatial distribution of photosynthetically active radiation (PAR) in a heterogeneous cotton canopy based on a geo-statistical sampling method. Field experiments were conducted in 2011 and 2012 in Anyang, Henan, China. Field plots were arranged in a randomized block design with the main plot factor representing the plant density. There were 3 replications and 6 densities used in every replicate. The six plant density treatments were 15,000, 33,000, 51,000, 69,000, 87,000 and 105,000 plants ha−1. The following results were observed: 1) transmission within the canopy decreased with increasing density and significantly decreased from the top to the bottom of the canopy, but the greatest decreases were observed in the middle layers of the canopy on the vertical axis and closing to the rows along the horizontal axis; 2) the transmitted PAR (TPAR) of 6 different cotton populations decreased slowly and then increased slightly as the leaves matured, the TPAR values were approximately 52.6–84.9% (2011) and 42.7–78.8% (2012) during the early cotton developmental stage, and were 33.9–60.0% (2011) and 34.5–61.8% (2012) during the flowering stage; 3) the Leaf area index (LAI) was highly significant exponentially correlated (R2 = 0.90 in 2011, R2 = 0.91 in 2012) with the intercepted PAR (IPAR) within the canopy; 4) and a highly significant linear correlation (R2 = 0.92 in 2011, R2 = 0.96 in 2012) was observed between the accumulated IPAR and the biomass. Our findings will aid researchers to improve radiation-use efficiency by optimizing the ideotype for cotton canopy architecture based on light spatial distribution characteristics.

Effects of plant density on cotton yield components and quality

Abstract Yield and fiber quality of cotton even varies within locules in a boll, but it is not clear how yield components and quality parameters are altered across seed positions of a locule (SPL). A field experiment was arranged in a split plot design with transgenic insect resistant Bt (Bacillus thuringiensis) cotton hybrid cultivar CRI75 and conventional cultivar SCRC28 as the main plots, and three plant densities (15 000, 51 000 and 87 000 plants ha−1) as the subplots in 2012 and 2013 at Anyang, Henan Province, China. Cotton was hand harvested by node and fruiting position, and then seeds of the first fruiting position bolls from nodes 6–10 were separated by SPL. The effects of plant density on lint yield, fiber quality, especially across SPL were determined. It was showed that plant densities of 51 000 and 87 000 plants ha−1 increased lint yield by 61.3 and 65.3% in 2012 and 17.8 and 15.5% in 2013 relative to low plant density (15 000 plants ha−1), however, no significant difference was observed between 51 000 and 87 000 plants ha−1. The number of bolls (boll density) increased while boll weight decreased as plant density raised, and no significant changes occured in lint percentage in 2013 but increased with plant density in 2012. The number of bolls in upper nodes and distal fruiting positions, the number of seeds per boll, seed area (SA) and seed vigor index increased with decreasing plant density. Seed area was found to be greater from the base to the middle compared to the apex of a locule. Mote frequency (MF) increased as plant density increased, and fiber quality was the best at the middle of the locule regardless of plant density. As the number of fibers per seed area is genetically determined, adjusting plant density to produce more seeds and greater seed area can be a potentially promising alternative to improve lint yield in cotton. These findings might be of great importantance to cotton breeding and filed management.

Response of cotton phenology to climate change on the North China Plain from 1981 to 2012

To identify countermeasures for the impacts of climate change on crop production, exploring the changes in crop phenology and their relationship to climate change is required. This study was based on cotton phenology and climate data collected from 13 agro-meteorological experimental stations and 13 meteorological stations on the North China Plain from 1981 to 2012. Spatiotemporal trends in the cotton phenology data, lengths of the different growing phases, mean temperatures, and rainfall were analyzed. These results indicated that warming accelerated cotton growth, advanced cotton phenology, and shortened the growing period of cotton. However, harvest dates were significantly delayed at 8 (61.5%) stations, the length of both the flowering-boll opening and boll opening-harvest periods increased at 10 (77.0%) stations, and a positive correlation was found between the mean temperature and the length of the whole growing period at 10 (77.0%) stations. Therefore, cotton practices and cultivars on the North China Plain should be adjusted accordingly. The response of cotton phenology to climate change, as shown here, can further guide the development of options for the adaptation of cotton production in the near future.

Study on Light Interception and Biomass Production of Different Cotton Cultivars

Identifying the characteristics of light interception and utilization is of great significance for improving the potential photosynthetic activity of plants. The present research investigates the differences in absorbing and converting photosynthetically active radiation (PAR) among various cotton cultivars. Field experiments were conducted in 2012, 2013 and 2014 in Anyang, Henan, China. Ten cultivars with different maturity and plant architectures were planted at a density of 60,000 plants ha-1 in randomized blocks, with three replicates. The spatial distribution of light in canopy was measured and quantified with a geo-statistical method, according to which the cumulative amount of intercepted radiation was calculated by Simpson 3/8 rules. Finally, light interception was analyzed in association with the biomass accumulation of different cultivars. The key results were: (1) late-maturing varieties with an incompact plant architecture captured more solar radiation throughout the whole growth period than middle varieties with columnar architecture and even more than early varieties with compact architecture, and they produced more biomass; (2) the highest PAR interception ratio and the maximum biomass accumulation rate occurred during the blossoming and boll-forming stage, when leaf area index (LAI) reached its peak; (3) the distribution within the canopy presented a significant spatial heterogeneity, and at late growing stage, the PAR was mainly intercepted by upper canopies in incompact-type plant communities, but was more homogeneous in columnar-type plants; however, the majority of radiation was transmitted through the canopy in compact-type colonies; (4) there was not a consistent variation relationship between the cumulative intercepted PAR (iPAR) and biomass among these cultivars over the three years of the study. Based on these results, we attempted to clarify the distinction in light spatial distribution within different canopies and the patterns of PAR interception in diverse cotton cultivars with different hereditary characters, thereby providing a significant basis for researchers to select cultivars with appropriate growth period and optimal plant architecture for improvement of light interception and utilization.

Root growth and spatial distribution characteristics for seedlings raised in substrate and transplanted cotton

In this study, transplanting cotton seedlings grown in artificial substrate is considered due to recent increased interest in cotton planting labor saving approaches. The nursery methods used for growing cotton seedlings affect root growth. However, the underlying functional responses of root growth to variations in cotton seedling transplanting methods are poorly understood. We assessed the responses of cotton (Gossypium hirsutum L.) roots to different planting methods by conducting cotton field experiments in 2012 and 2013. A one-factor random block design was used with three replications and three different cotton planting patterns (substrate seedling transplanted cotton (SSTC), soil-cube seedling transplanted cotton (ScSTC) and directly sown cotton (DSC). The distributions and variances of the root area density (RAD) and root length density (RLD) at different cotton growing stages and several yield components were determined. Overall, the following results were observed: 1) The RAD and RLD were greatest near the plants (a horizontal distance of 0 cm) but were lower at W20 and W40 cm in the absence of film mulching than at E20 and E40 cm with film mulching. 2) The roots were confined to shallow depths (20–40 cm), and the root depths of SSTC and DSC were greater than the root depths of ScSTC. 3) Strong root growth was observed in the SSTC at the cotton flowering and boll setting stages. In addition, early onset root growth occurred in the ScSTC, and vigorous root growth occurred throughout all cotton growth stages in DSC. 4) The SSTC plants had more lateral roots with higher root biomass (RB) than the ScSTC, which resulted in higher cotton yields. However, the early onset root growth in the ScSTC resulted in greater pre-frost seed cotton (PFSC) yields. These results can be used to infer how cotton roots are distributed in soils and capture nutrients.

Estimating light interception using the color attributes of digital images of cotton canopies

Abstract Crop growth and yield depend on canopy light interception (LI). To identify a low-cost and relatively efficient index for measuring LI, several color attributes of red-green-blue (RGB), hue-saturation-intensity (HSI), hue-saturation-value (HSV) color models and the component values of color attributes in the RGB color model were investigated using digital images at six cotton plant population densities in 2012–2014. The results showed that the LI values followed downward quadratic curves after planting. The red (R), green (G) and blue (B) values varied greatly over the years, in accordance with Cais research demonstrating that the RGB model is affected by outside light. Quadratic curves were fit to these color attributes at six plant population densities. Additionally, linear regressions of LI on every color attribute revealed that the hue (H) values in HSI and HSV were significantly linearly correlated with LI with a determination coefficient (R 2 )≥0.89 and a root mean square error (RMSE)=0.05. Thus, the H values in the HSI and HSV models could be used to measure LI, and this hypothesis was validated. The H values are new indexes for quantitatively estimating the LI of heterogeneous crop canopies, which will provide a theoretical basis for optimizing the crop canopy structure. However, further research should be conducted in other crops and under other growing and environmental conditions to verify this finding.