Abstract
Field studies were carried out for the purpose of evaluating fertilizer nitrogen (N) recovery of upland cotton by use of the difference technique. The treatments under study included : i) check (no fertilizer N applied), ii) standard approach (preplant and sidedress), iii) feedback approach (based upon soil and plant factors), and iv) 2X feedback approach. The studies were carried out at two locations Maricopa (MAC) and Marana (MAR). MAC is a low elevation location with a coarser textured soil compared to the MAR location. 'DPL-20' was the variety used in both locations, except for the early years at MAC where 'DPL-90' was used. The sources of fertilizer N were urea and ammonium sulphate, which were sidedress and split applied. In general, for the MAC location the final N fertilizer rates (NFR) applied were higher than for MAR due to higher yield potentials. The total N uptake increased as the NFR increased. The N use efficiency (NUE) values were reduced as NFR increased. The N fertilizer uptake (NFU) showed a decreasing pattern in the first years, and then an increasing trend; which was coupled with rather high amounts of N taken up in the check plot (soil N mineralized). When the N uptake in the check plot was high, NFU values were low, and vice versa. At MAC the N uptake in the check plot, apparently due to mineralized soil N revealed a slight increasing trend during the first years and then, after the fourth year, a rapid reduction of the mineralized soil N (check plot). A similar pattern was observed for MAR, although the total amount of N taken up was smaller compared to the MAC location.
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Claims 8
Claim · model-written summary
Final nitrogen fertilizer rates were generally higher at MAC than MAR.
Verbatim
e0“for the MAC location the final N fertilizer rates (NFR) applied were higher than for MAR”
t0“upland cotton”
Claim · model-written summary
Total nitrogen uptake increased with fertilizer nitrogen rate.
Verbatim
e0“The total N uptake increased as the NFR increased”
t0“upland cotton”
Claim · model-written summary
Nitrogen use efficiency declined as fertilizer nitrogen rate increased.
Verbatim
e0“The N use efficiency (NUE) values were reduced as NFR increased”
t0“upland cotton”
Claim · model-written summary
Fertilizer nitrogen uptake decreased in early years and increased later.
Not reportedDirection
Verbatim
e0“The N fertilizer uptake (NFU) showed a decreasing pattern in the first years, and then an increasing trend”
t0“upland cotton”
Claim · model-written summary
Fertilizer nitrogen uptake was low when check-plot nitrogen uptake was high, and vice versa.
Verbatim
e0“When the N uptake in the check plot was high, NFU values were low, and vice versa”
t0“upland cotton”
Claim · model-written summary
MAC check-plot nitrogen uptake rose slightly in early years.
Verbatim
e0“At MAC the N uptake in the check plot, apparently due to mineralized soil N revealed a slight increasing trend during the first years”
t0“upland cotton”
Claim · model-written summary
After the fourth year, MAC check-plot mineralized soil nitrogen declined rapidly.
Verbatim
e0“after the fourth year, a rapid reduction of the mineralized soil N (check plot)”
t0“upland cotton”
t1“At MAC the N uptake in the check plot”
Claim · model-written summary
MAR showed a similar temporal nitrogen-uptake pattern, at a smaller total amount than MAC.
Verbatim
e0“A similar pattern was observed for MAR, although the total amount of N taken up was smaller compared to the MAC location”
t0“upland cotton”