Premium
Seasonal Nitrogen and Carbohydrate Partitioning in Forage Brassicas
Author(s) -
Guillard Karl,
Pietrzyk Stephen W.,
Allinson Derek W.,
Cassida Kimberly A.,
Wiedenhoeft Mary Hagemann,
Hough Robert L.,
Barton Barbara A.
Publication year - 1995
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1995.00021962008700030028x
Subject(s) - loam , forage , brassica oleracea , brassica rapa , growing season , biology , agronomy , nitrate , nitrogen , botany , horticulture , zoology , brassica , chemistry , soil water , ecology , organic chemistry
Nitrate toxicosis is more prevalent when ruminants consume forages high in NO 3 and low in readily fermentable carbohydrates. Environmental conditions vary with season and may differentially affect herbage N and total nonstructural carbohydrate (TNC) composition. Experiments were conducted to determine the concentrations and partitioning of NO 3 −N, total N (TN), TNC, and inorganic N in summerand autumn‐grown brassicas in CT. Kale ( Brassica oleracea var. acephala DC.), rape ( B. napus L.), turnip ( B. rapa L.), and tyfon [ B. rapa L. ✕ B. pekinensis (Lour.) Rupr.] were established in June and August of 1988 and 1990 on a Paxton fine sandy loam soil (coarse‐loamy, mixed, mesic Typic Dystrochrept). The experimental design in each season was a split‐plot, with species as main plots and sampling dates [30, 60, 90, and 120 days after seeding (DAS)] as subplots. Concentrations of NO 3 −N and TN decreased with time in both seasons, but the rate of decline for both constituents was generally greater during the summer than autumn. Concentrations of TNC in the whole plant and most plant parts increased with time and peaked at 90 or 120 DAS in both seasons. Inverse relationships were found between TN and TNC (except in laminae), and between NO 3 −N and TNC (except in roots). Concentrations of NO 3 −N were relatively low in the whole plant, central midrib‐petioles, stems, and roots when the concentrations of TN were <29 g kg −1 , but increased linearly when TN was greater than this. Concentrations of NO 3 −N increased linearly in laminae only when TN concentrations were >54 g kg −1 . Whole‐plant inorganic N concentrations, as a percentage of TN, were <10% at 60 DAS. The potential risk for NO 3 toxicosis in ruminants is higher if animals graze brassicas before 60 DAS than if they graze brassicas after 60 DAS.