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Organic & Integrated Tree Fruit Production

Thursday, January 18, 2018

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6001. Russell, J.S. and C.H. Williams. 1982. Biogeochemical interactions of carbon, nitrogen, sulfur, and phosphorus in Australian agroecosystems.. IN: J.R. Freney and I.E. Galbally (eds.). Cycling of C,N,S, and P in terrestrial/aquatic ecosystems..
An excellent review article looking at nutrient cycling and gains and losses over time under different agricultural management. Estimates that over 3 million tons C are tied up in soil organic matter additions each year in Australian farmland. SOM levels are higher now than the native condition under systems that have used a legume pasture in the rotation. There was a generally downward trend in the soil C:N over the first 25 yr of OM accumulation. A WWPP rotation slightly increased SOM, while WWWP decreased it slightly, and fallow systems decreased it significantly. Increases in SOM increased the water-stable aggregates in the soil and improved infiltration. Leguminous pastures had an acidifying effect on the underlying soil.

9444. Kitchen, N.R., D.G. Westfall and G.A. Peterson. 1989. Potential N and C mineralization in dryland no-till cropping soils as influenced by N fertilization management.. Agronomy Abstracts, Amer. Soc. Agron., Madison, WI. p. 244..
A study was conducted to determine the effects of N fertilization on potential mineralization of N and C in no-till cropped soils. A 30 day incubation was performed on soils from Sterling and Stratton, Colorado, sampled at 0-5 and 5-15 cm depths over and between crop rows. Nitrogen fertilization treatments were banded and broadcast UAN at 0, 34, and 90 kg N/ha. Net N mineralization rate was approximately 0.5 mg N/kg /soil-day greater in the Stratton 0-5 cm soil over the row than between the row. The same trend was found with C mineralization rates. Sterling soil from the 5-15 cm depth decreased in the ratio of C/N mineralized with increasing rate of N fertilization, but was not different as a result of fertilization placement. The results of this study illustrate the interaction of N and C turnover in soils.

9569. Cochran, V.L., L.F. Elliott and R.I. Papendick. 1980. Carbon and nitrogen movement from surface-applied wheat straw.. Soil Science Soc. Am. J. 44:978-982..
The N immobilization potential of surface-applied wheat straw as compared with incorporated straw was evaluated in the laboratotory with soil columns. The columns were leached weekly and C and N content of the leachate was determined. Leachate C/N ratios for straw alone exceeded 20:1 on several occasions and reached a maximum of 56, indicating a potential for N immobilization. Less than 5% of the total C in the straw was recovered in the leachates, providing an inmobilizatoin potential of <5 kg N//ha. Leachate C/N ratios from 1-, 2-, and 4-cm deep soil columns with surface-applied wheaat straw and no ferilizer N ranged up to 55:1; 30:1 and 22:1, respectively, while the highest leachate C/N ratio from the 4-cm mixed straw treatment was 30:1. A significant percentage of mineralized N was immobilized in the 1 and 2 cm of soil by surface residues. Much less N was immobilized in the 4-cm soil columns. Thus, placement of fertilizer N several centimenters below the soil surface would alleviate possible N immobilization from organic C leached from surface crop residues. The amount of applied N recovered in the leachate during 9 weeks of incubation ranged from 60 to 70% for all soil column treatments with or without surface straw. There was no significant difference between treatments. In contrast, the recovery of applied N from the mixed straw treatment was only 36% indicating a much greater potential for N immobilization with mixed than with surface straw. The quantity of the fertilizer N added probably masked the immobilization potential of surface residues. Fertilizer N stimulated early release of C from the straw alone treatment. But after 9 weeks of incubation the overall C loss from both fertilized and unfertilized straw was about 30%.

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