Real-time Measures of Canopy Size as a Basis for Spatially Varying Nitrogen Applications to Winter Wheat sown at Different Seed Rates
By G. A. Wood, J. Welsh, R. Godwin, J. C. Taylor, R. Earl, S. M. Knight. 2003
74 citations recorded by the source corpus.
Abstract Experiments at two sites growing winter wheat show that in order to manage a wheat canopy more effectively, the use of specific remote sensing techniques both to monitor crop canopy expansion, and to determine variable nitrogen applications at key timings is required. Variations in seed rate were used to achieve a range of initial crop structures, and treatments were compared to standard farm practice. In the first year, the effect of varying seed rate (250, 350 and 450 seeds m −2 ) on crop structure, yield components and grain yield, was compared to the effects of underlying spatial variation. Plant populations increased up to the highest rate, but shoot and ear populations peaked at 350 seeds m −2 . Compensation through an increased number of grains per ear and thousand grain weight resulted in the highest yield and gross margin at the lowest seed rate. In later experiments, the range of seed rates was extended to include 150 seeds m −2 , each sown in 24 m wide strips split into 12 m wide halves. One half received a standard nitrogen dose of 200 kg [N] ha −1 , the other a variable treatment based on near ‘real-time’ maps of crop growth. Both were split into three applications, targeted at mid-late tillering (early March), growth stages GS30-31 (mid April) and GS33 (mid May). At each timing, calibrated aerial digital photography was used to assess crop growth in terms of shoot population at tillering, and canopy green area index at GS30-31 and GS33. These were compared to current agronomic guidelines. Application rates were then varied below or above the planned amount where growth was above- or below-target, respectively. In the first field, total nitrogen doses in the variable treatments ranged from 188 to 243 kg [N] ha −1 , which gave higher yields than the standards at all seed rates in the range 0·36–0·78 t ha −1 and gross margins of £17 to £60 ha −1 . In the second field, variable treatments ranged from 135 to 197 kg [N] ha −1 that resulted in lower yields of −0·32 to +0·30 t ha −1 . However, in three out of the four seed rates, variable treatments produced higher gross margins than the standard, which ranged from £2 to £20 ha −1 . In both fields, the greatest benefits were obtained where the total amount of applied nitrogen was similar to the standard, but was applied variably rather than uniformly along the strips. Simple nitrogen balance calculations have shown that variable application of nitrogen can have an overall effect on reducing the nitrogen surplus by one-third.
Subfields: Agronomy and Crop Science, Ecology, Global and Planetary Change
View Paper: https://www.semanticscholar.org/paper/8d7104bd37f7f28efc55c2d482ad7cadb7b3164c
How researchers see this paper
The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.
In Agronomy and Crop Science
In Ecology
In Global and Planetary Change
Citations in the corpus
- Grain yield, and dry matter and nitrogen accumulation and remobilization in durum wheat as affected by variety and seeding rate (2006, background): “Conversely, Carr et al. (2003) and ood et al. (2003) found that grain yield of wheat was higher ith 250 than with 450 seeds m−2.”
- DUAL PURPOSE WHEAT FOR FORAGE AND GRAIN YIELD IN RESPONSE TO CUTTING, SEED RATE AND NITROGEN (2011, background): “Lower seed rate (100 kg ha) gave maximum yield compared to higher seed rate of 150 kg hawhich may be due to the fact that wheat have the potential to compensate for low seed rate if the environmental conditions are favorable (Carr et al., 2003; Wood et al., 2003).”
- Topdressing nitrogen recommendation for early rice with an active sensor in south China (2014, methodology): “2004; Nguyen and Lee 2006) and guiding N fertilization (Raun et al. 2002; Wood et al. 2003; Welsh et al. 2003; Raun et al. 2005).”
- Grain yield, dry matter accumulation and remobilization, and root respiration in winter wheat as affected by seeding rate and root pruning. (2010, unknown): “Many studies have foundapositive correlation between seeding rate and both grain yield and mean kernel weight (Blue et al., 1990; Geleta et al., 2002; Wood et al., 2003; Arduini et al., 2006), but our study suggests that this correlation depends on availability of moisture.”
- Integrated weed management in wheat (2011, background): “Conversely, Carr et al. (2003) and Wood et al. (2003) found that grain yield of wheat was higher with 250 than with 450 seeds m-2.”