Agronomic studies on soybean (Glycine max (L.) Merrill) in the dry seasons of the tropics. I. Limits to yield imposed by phenology

1991 ◽  
Vol 42 (7) ◽  
pp. 1075 ◽  
Author(s):  
JD Mayers ◽  
RJ Lawn ◽  
DE Byth
Keyword(s):  
Leaf Area ◽  
Biomass Production ◽  
Seed Yield ◽  
Management Practices ◽  
Dry Season ◽  
Canopy Development ◽  
Precocious Flowering ◽  
The Tropics ◽  
Area Development ◽  
Leaf Area Development

An analysis was undertaken of the development, growth and seed yield of irrigated soybean crops grown during the dry season of the semi-arid tropics in north-western Australia, to establish yield potentials and identify major climatic or physiological constraints. Ten tropically adapted genotypes were grown at three sowing times, using agronomic management practices designed to maximize productivity and minimize constraints due to water supply, fertility, weeds and insects. In addition to phenology, seed yield, dry matter (DM) accumulation, and seed and plant morphological traits, measurements were made at the beginning and end of flowering of DM accumulation, leaf area development and interception of photosynthetically active radiation (PAR). Harvest indices were generally large, but maximum seed yields were only c. 3 t ha-1, apparently because of inadequate biomass production. The analysis of growth and development suggested that DM accumulation during the vegetative phase was limited primarily by cumulative PAR interception by the crop canopy rather than the efficiency of conversion of intercepted PAR. In turn, both cumulative PAR interception, and canopy leaf area development, were constrained by precocious flowering, induced by the comparatively short-day/warm temperature conditions of the dry season. It was concluded that yield improvement strategies for the dry season will need to be based on agronomic and/or breeding strategies to enhance canopy development and improve biomass production.

Agronomic studies on soybean (Glycine max (L.) Merrill) in the dry season of the tropics. II. Interaction of sowing date and sowing density

1991 ◽  
Vol 42 (7) ◽  
pp. 1093 ◽  
Author(s):  
JD Mayers ◽  
RJ Lawn ◽  
DE Byth
Keyword(s):  
Biomass Production ◽  
Seed Yield ◽  
Management Practices ◽  
Interaction Analysis ◽  
Sowing Date ◽  
Dry Season ◽  
High Yield ◽  
Total Biomass ◽  
Wet Season ◽  
Precocious Flowering

An analysis was undertaken of the development, growth and seed yield of irrigated soybean crops grown during the dry season in the semi-arid tropics of north-western Australia, to establish whether constraints to seed yield induced by precocious flowering could be overcome agronomically by manipulating sowing date and/or sowing density. Three agronomically improved cultivars and a later-flowering landrace cultivar were tested using irrigation, fertility and pest management practices designed to minimize constraints to yield. Maximum seed yields were 3.5-4.0 t ha-1, with large genotype x sowing date x sowing density interaction. Analysis of vegetative growth showed that higher sowing densities stimulated more rapid leaf area development and earlier canopy closure, and enhanced total biomass production. However, very high sowing densities were needed to maximize yields of most genotypes, while lodging precluded high yield being realized from the greater biomass production of high density sowings of the landrace genotype. Delaying sowing from April to June delayed flowering, increased biomass production and marginally enhanced yields, but not sufficiently to offset potential problems caused by maturation into hot dry conditions prior to the wet season. It was concluded that agronomic strategies alone were insufficient to overcome the constraints to yield of present soybean genotypes in the dry season.

Agronomic studies on soybean (Glycine max (L.) Merrill) in the dry season of the tropics. III. Effect of artificial photoperiod extension on phenology, growth and seed yield

1991 ◽  
Vol 42 (7) ◽  
pp. 1109 ◽  
Author(s):  
JD Mayers ◽  
RJ Lawn ◽  
DE Byth
Keyword(s):  
Seed Yield ◽  
Dry Season ◽  
Yield Potential ◽  
Wet Season ◽  
Canopy Development ◽  
North West ◽  
Precocious Flowering ◽  
Natural Photoperiod ◽  
Artificial Photoperiod ◽  
Delayed Flowering

Soybean cultivars developed for the tropical wet season performed poorly when grown in the dry season in north-west Australia. The proposition that breeding for later flowering time might enhance yields was tested by using artificial photoperiod extension (14 h day-1 for 28 days post-emergence) to delay flowering of field plots of agronomically improved genotypes. Canopy development and interception of photosynthetically active radiation (PAR), dry matter (DM) accumulation, seed yield and seed composition were examined, and compared with that from plants grown under natural photoperiods. Photoperiod extension delayed flowering an average 24 days, and maturity by an average 14.5 days, the effect being greater in the earlier-flowering genotypes. Differences among genotypes and photoperiod treatments in above-ground DM at the beginning and end of flowering were almost entirely due to the consequences of differences in phenology for cumulative PAR interception. DM at maturity was a simple linear function of crop duration (r2 = 0.95**), while seed yield exhibited an optimum-type response with DM ( R2 = 0.79**). The net consequence was that photoperiod extension increased DM production by an average 2.23 t ha-1 and seed yield by an average 0.65 t ha-1. The analyses suggested that a crop duration of c. 143-146 days would be needed to maximize seed yield under the agronomic conditions of the study, whereas the longest duration among the agronomically improved genotypes under natural photoperiod conditions was 136 days. It was concluded that breeding to constrain precocious flowering under short day conditions would be a viable strategy to improve the yield potential of soybean in the dry season.

Effects of nitrogen supply on canopy development of maize and sunflower

2011 ◽  
Vol 62 (12) ◽  
pp. 1045 ◽  
Author(s):  
A. M. Massignam ◽  
S. C. Chapman ◽  
G. L. Hammer ◽  
S. Fukai
Keyword(s):  
Leaf Area ◽  
Plant Density ◽  
Carbon Assimilation ◽  
Leaf Nitrogen ◽  
Area Index ◽  
Canopy Development ◽  
N Limitation ◽  
N Supply ◽  
Area Development ◽  
Leaf Area Development

Nitrogen (N) limitation reduces canopy carbon assimilation by directly reducing leaf photosynthesis, and by developmentally reducing the rate of new leaf area development and accelerating leaf senescence. Effective use of N for biomass production under N limitation may be considered to be a result of a trade-off between the use of N to maintain high levels of specific leaf nitrogen (SLN the amount of N per unit leaf area) for high photosynthetic rate versus using N to maintain leaf area development (leaf area index – LAI). The objective here is to compare the effects of N supply on the dynamics of LAI and SLN for two crops, maize (Zea mays L.) and sunflower (Helianthus annuus L.) that contrast in the structure and development of their canopy. Three irrigated experiments imposed different levels of N and plant density. While LAI in both maize and sunflower was reduced under N limitation, leaf area development was more responsive to N supply in sunflower than maize. Observations near anthesis showed that sunflower tended to maintain SLN and adjust leaf area under reduced N supply, whereas maize tended to maintain leaf area and adjust SLN first, and, when this was not sufficient, SLN was also reduced. The two species responded differently to variation in N supply, and the implication of these different strategies for crop adaptation and management is discussed.

Photosynthetic Physiology of Spur Pruned and Minimal Pruned Grapevines

1992 ◽  
Vol 19 (3) ◽  
pp. 309 ◽  
Author(s):  
WJS Downton ◽  
WJR Grant
Keyword(s):  
Leaf Area ◽  
Dry Weight ◽  
Photosynthetic Performance ◽  
Total Carbon ◽  
Carbon Gain ◽  
Canopy Development ◽  
Photosynthetic Rates ◽  
Photosynthetic Physiology ◽  
Area Development ◽  
Leaf Area Development

Canopy development, photosynthetic performance and yield characteristics of Riesling grapevines managed by either conventional spur pruning or minimal pruning were compared over a growing season. Leaf area development 4-5 weeks after budburst was 4-5-fold greater on the minimal pruned vines due to the 6-7-fold greater number of buds that burst to produce shoots. By time of flowering (8 weeks after budburst) there was less than a 2-fold difference between the pruning treatments in leaf area per vine. At time of harvest the leaf area of spur pruned vines on a Y-shaped trellis exceeded that of minimal pruned vines. Average photosynthetic rates of leaves on shoots on minimal pruned vines were 40% higher than on spur pruned vines at 4 weeks after budburst, but average rates were similar the following week and thereafter. Calculated instantaneous photosynthetic rates for entire vines were 3-6-fold higher for the minimal pruned vines at 4-5 weeks after budburst. However, by time of flowering, vines in both treatments had similar photosynthetic rates. At harvest, spur pruned vines showed somewhat greater instantaneous carbon gain than minimal pruned vines. Carbon gain per vine per day estimated from hourly measurements of irradiance over the canopy showed a similar trend to the instantaneous rates. Leaf conductances did not differ with pruning treatment. Calculated instantaneous water loss per vine was 2-5-fold higher for minimal pruned vines 4-5 weeks after budburst, but from flowering onwards spur pruned vines were likely to use more water than minimal pruned vines. Minimal pruned vines yielded twice the quantity of fruit of spur pruned vines, but only one-quarter the dry weight of new canes. Total carbon invested in fruit, new canes and leaves, however, was similar in both pruning treatments, accounting for 60-70% of the estimated carbon gain by the vines.

Leaf Area Development, Light Interception, and Yield among Switchgrass Populations in a Short‐Season Area

Crop Science ◽  
1998 ◽  
Vol 38 (3) ◽  
pp. 827-834 ◽  
Author(s):  
I. C. Madakadze ◽  
B. E. Coulman ◽  
P. Peterson ◽  
K. A. Stewart ◽  
R. Samson ◽  
...  
Keyword(s):  
Leaf Area ◽  
Light Interception ◽  
Short Season ◽  
Area Development ◽  
Leaf Area Development

Leaf area development and yield of cassava in response to pruning of shoots and the late supply of nitrogen and potassium

2020 ◽  
Vol 112 (2) ◽  
pp. 1406-1422
Author(s):  
Lydia Helena S.O. Mota ◽  
Adalton M. Fernandes ◽  
Natália S. Assunção ◽  
Hugo M.F. Leite
Keyword(s):  
Leaf Area ◽  
Area Development ◽  
Leaf Area Development
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