Farm Table says:
What is the problem?
The aim of this series of trials was to investigate the response cotton growth and lint yield to applied N on two different irrigation systems to determine if irrigation system influences the recovery fertilizer N.
What did the research involve?
Four trials were planted, two overhead and two flood-furrow irrigated. However, only three are reported here, one overhead site and both flood sites. The second overhead site had other influences on lint yield that impacted on the N treatments. Soil types at each site are broadly classified as Vertosols. Pre-season soil tests indicated that the sites would be responsive to N application with N contents in the 0-90cm soil profile of 100, 115 and 45 kg N/ha for Overhead 1, Flood 1 and Flood 2, respectively.
What were the key findings?
- Increasing Nitrogen (N) application rate increased the Vegetative Growth Rate but did not reliably increase node number and total bolls per plant.
- N uptake increased with increasing N application at the overhead site and one of the flood sites, however; more N in the plant did not mean higher lint yields.
- The lint yield response to applied nitrogen (N) plateaued at lower than expected rates; 85 kg N/ha at the overhead site, 130 kg N/ha and 100 kg N/ha at the two flood sites.
- Nitrogen recovery in the plant at defoliation was around 13-30 percent higher in the overhead irrigation system compared to the flood systems.
- The amount of lint produced for each kilogram of N taken up by the crop, where the yield plateaued, was very similar across the sites at 17.9, 17.3 and 18.6 kg lint/kg of crop N uptake for the overhead and two flood sites, respectively.
- Increasing N application did not reliably result in more mineral N at the end of the season.
Increasing N application did not always lead to an increase in the amount of residual postseason N, meaning that this can become a very inefficient and uncontrolled way applying N to a subsequent crop.