An Apparatus for Application of Nitrogen-15 Fertilizers Through Buried Drip Tubing
1995
McGee, E. A. | Thompson, T. L. | McCreary, T. W.
This study evaluated a new apparatus for applying ¹⁵N by fertigation to subplots under buried drip irrigation. Leaf lettuce (Lactuca sativa L. cv. Waldmann's Green) was planted in one unfertilized buried-drip-irrigated plot (4.06 by 53.34 m) with four north-south beds. Six subplots (1.02 by 2.00 m) were established by placing a ¹⁵N injection apparatus into the drip tubing. Nitrogen-rate treatments (71 and 176 kg ha⁻¹) were replicated three times. Low- and high-N plots received 1.60 and 1.15 atom % ¹⁵N urea applied at five times during the season. Plants were harvested at specific positions within and near the subplots. Uniform recovery of ¹⁵N by plants within subplots occurred. Uptake of ¹⁵N by plants was observed up to 45 cm outside subplots in the north-south directions and in plants on beds immediately adjacent to the subplots. Uptake outside the subplots in the north-south directions (apparent lateral movement) was no more than 21% of total ¹⁵N uptake.
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