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Critical Nitrate Levels for Growth of Italian Ryegrass 1
Author(s) -
Hylton L. O.,
Williams D. E.,
Ultrich A.,
Cornelius D. R.
Publication year - 1964
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1964.0011183x000400010006x
Subject(s) - crop , range (aeronautics) , biology , agronomy , engineering , aerospace engineering
ITALIAN ryegrass in the Pacific coast rangelands frequently requires nitrogen fertilizer for sa t i s fac tory growth and maintenance. The need for N on these rangelands has been indicated by soil analyses and pot tests. No attempt has been made, however, to utilize critical nitrate-concentration levels in specific grass tissue for rangeland evaluations. This approach involves the concept of the critical nutrient-concentration which has been denned as that nutrient concentration at which growth first begins to decrease and is located within the transition zone that separates the zone of deficiency from the zone of adequacy (12). The critical level per se can only be determined when all nutrients, except the one under study, are supplied in ample amounts and all other environmental factors, including water are favorable for growth. In this paper the critical nitrate-N level is indicated by the value on the calibration curve where the slope at dy/dx is 1.0. Certain parts of a plant and forms of N reflect the internal status of N better than others. Therefore, it has been found important to evaluate, chemically and mathematically, several forms of N in each of several plant tissues (1, 2, 3, 10, 11). Most of these studies indicate that the unelaborated form, nitrate-N, is the best form of N to determine in dried plant tissue to reflect the internal status of N. Basic information is needed to estimate the N status of forage plants in their natural habitat with increased precision if progress is to be made in better rangeland management practices. The present study was designed to achieve this goal by determining the most sensitive and most reliable plant tissue to indicate the nitrate-N status in Italian ryegrass, Lolium multiflorurn Lam. Tifton #1, grown in the greenhouse. The results show the relation of top growth to nitrate-N concentrations in six plant parts. Critical nitrate-N levels were estimated from these calibration curves.