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Laura Elisa Acuña-Maldonado, Michael W. Smith, Niels O. Maness, Becky S. Cheary, Becky L. Carroll, and Gordon V. Johnson

Nitrogen was applied to mature pecan (Carya illinoinensis Wangenh. C. Koch.) trees annually as a single application at 125 kg·ha-1 N in March or as a split application with 60% (75 kg·ha-1 N) applied in March and the remaining 40% (50 kg·ha-1 N) applied during the first week of October. Nitrogen treatment did not affect yield, and had little effect on the amount of N absorbed. Nitrogen absorption was greater between budbreak and the end of shoot expansion than at other times of the year. Substantial amounts of N were also absorbed between leaf fall and budbreak. Little N was absorbed between the end of shoot expansion and leaf fall, or tree N losses met or exceeded N absorption. Pistillate flowers and fruit accounted for a small portion of the tree's N; ≈0.6% at anthesis and 4% at harvest. The leaves contained ≈25% of the tree's N in May and ≈17% when killed by freezing temperatures in November. Leaves appeared to contribute little to the tree's stored N reserves. Roots ≥1 cm diameter were the largest site of N storage during the winter. Stored N reserves in the perennial parts of the tree averaged 13% of the tree's total N over a three year period. Current year's N absorption was inversely related to the amount of stored N, but was not related to the current or previous year's crop load.

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Mark Gaskell and Richard Smith

-farm sources, and purchased organic fertilizers. When discussing organic N fertility programs, it is important to distinguish between short-term and long-term effects. Studies have shown that the total supply of N from SOM on organic farms may be in excess of

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Pengpeng Duan, Ying Sun, Yuling Zhang, Qingfeng Fan, Na Yu, Xiuli Dang, and Hongtao Zou

). Soil mineral N [including nitrate (NO 3 − )–N and ammonia (NH 4 + )–N], soil soluble organic N, soil microbial biomass N, and soil fixed ammonium are important labile soil N fractions that are actively involved in N mineralization and immobilization

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Angela Y.Y. Kong, Cynthia Rosenzweig, and Joshua Arky

demand will also lead to the greatest loss of N in leachates compared with the other systems, 2) the organic N input with the lowest C:N ratio will release plant available N at a rate most closely synchronized with crop N demand, thereby leading to the

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Heidi J. Johnson, Jed B. Colquhoun, and Alvin J. Bussan

meal, to the most expensive product, fish powder ( Hartz and Johnstone, 2006 ). To remain cost effective, the amendments would need to consistently provide a significant increase in yield in comparison with other organic N sources. These products in

Open access

Derek J. Plotkowski and John A. Cline

in the orchard to increase organic N found in juice. Although there are practical limitations to the specific methods used here, learning how to use intentional measures in the orchard to address needs for cider production can reduce the need for

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Zhi Quan, Bin Huang, Caiyan Lu, Yi Shi, Yanhong Cao, Yongzhuang Wang, Chuanrui He, Guangyu Chi, Jian Ma, and Xin Chen

-TN analyzer (Multi N/C 3100; Analytik Jena, Germany) (extracts pass through 0.45-µm filter membrane before injection). Extractable organic N = TEN − NO 3 − -N − NH 4 + -N. The extracts were kept in polypropylene bottles in a −18 °C refrigerator before analysis

Open access

Amit Bhasin, Joan Davenport, Scott Lukas, Qianwen Lu, Gwen Hoheisel, and Lisa W. DeVetter

to evaluate the potential impacts of postharvest organic N fertilizer applications for the early fruiting northern highbush blueberry cultivar Duke. Specific objectives were to determine the effects of postharvest N fertilizer application on plant

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Zhongchun Jiang, Chenping Xu, and Bingru Huang

led to redistribution of reduced N (total N excluding nitrate-N) from perennial ryegrass roots and verdure to the leaves. Few studies of turfgrass have reported activities of enzymes in organic N metabolism of young and old leaves of plants under N

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David Granatstein, Joan R. Davenport, and Elizabeth Kirby

least expensive organic N source per dry kilogram N. Biologically fixed nitrogen also has a smaller carbon footprint than synthetic N which is commonly made from natural gas using considerable energy ( Camargo et al., 2013 ). Growers who have used or are