|Abstract or Summary
- A series of field experiments was established in 1978, 1979, and 1980 on Lower Klamath Lake where Mn deficiency of oats had been observed in previous years. The pH of the soils ranged from 7.6 to 8.3 and the organic matter content was between 17 and 19%. The objectives of the experiment were to (1) evaluate the effects of band application of different N sources with and without Mn on the Mn concentration and yield of barley and oats, (2) compare effects of band versus broadcast application of fertilizers on the Mn concentration and yield of barley and oats, and (3) determine the Mn critical level for barley and oats. Nitrogen was applied at 0, 22, or 45 kg N/ha as (NH₄)₂SO₄ (AmS), NH₄C1 (AmCl), Urea (Ur), granular urea-phosphate (UP 17-44), a ureaphosphoric acid solution (UP pH3), or a solution made from the granular urea-phosphate (UP). Phosphorus was applied at 0 or 19 kg P/ha as Ca(H₂PO₄ )₂ (MCP) or 25 kg P/ha in the UP solutions. Manganese was applied at 0 or 5.6 kg Mn /ha as MnS0₄ and copper was applied as CuSO₄, at 0 or 2.2 kg Cu/ha in 1978 with all treatments receiving 5.6 kg Cu/ha in 1979 and 1980. The treatments were arranged in a randomized block design with four replications. 'Cayuse' oats (Avena sativa L.) and 'Steptoe' barley (Hordeum vulgare L.) were planted at 110 kg/ha. In 1978, band application of 22 kg N/ha as AmS with P and Cu increased barley leaf Mn concentration and yield from 11 to 19 μg/g and from 3240 to 5420 kg/ha, respectively; oat leaf Mn concentration and yield were increased from 15 to 19 μg /g and from 1670 to 2560 kg/ha, respectively. Leaf Mn levels and yields were not increased by Ur fertilization. When Mn was applied, leaf Mn levels and yields were similar regardless of N source. Band application.Qf 45 kg N/ha as AmS with Mn, P, and Cu resulted in barley and oat yields of 6420 and 3060 kg/ha, respectively. Broadcast application of fertilizers did not increase leaf Mn concentration or yield. Similar results were obtained in 1979 and 1980. Responses to AmC1 were similar to those from AmS while UP materials were intermediate in effectiveness between Ur and AmS. The Mn critical level in leaf samples collected at mid-tillering is 22 μg/g in barley and 29 μg/g in oats. A series of laboratory experiments was designed to evaluate the effects of fertilizer application on the soil solution pH and Mn and P concentration. A centrifuge technique was developed which permitted the removal of an unaltered sample of the soil solution. Soil was collected adjacent to the field plots and placed in trays. Simulated fertilizer bands were added with fertilizer rates based on 25 cm row spacing. One week after fertilization the soil solution pH was decreased 0.82 and 0.54 units and increased 0.26 units by application of AmS, AmC1, and Ur, respectively, at 22 kg N/ha. When MCP was applied the pH was decreased from 8.12 to 7.01, 6.49, and 6.84 in the AmS, AmC1, and Ur bands, respectively. The soil solution Mn concentration increased from 0.04 to 0.18, 0.32, and 0.12 μg/m1 one week after fertilization in the AmS, AmC1, and Ur bands, respectively, when MCP was applied. After four weeks the Mn levels were 0.25, 0.23, and 0.03 μg /ml in the AmS, AmC1, and Ur bands, respectively. When Mn was included in fertilizer band with MCP the soil solution Mn concentration increased from 0.04 to 22.0, 16.6, and 26.5 μg/ml one week after fertilization in the AmS, AmC1, and Ur bands, respectively. The Mn levels in the AmS, AmC1, and Ur bands had fallen to 15.6, 12.1, and 4.9 μg/ml, respectively, after four weeks. Soil solution P concentration was markedly increased by P fertilization but was consistently decreased by Mn application at two and four weeks after fertilization.