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Uptake of foliar‐applied urea by winter wheat ( Triticum aestivum ): The influence of application time and the use of a new 15 N technique
Author(s) -
Powlson David S,
Poulton Paul R,
Møller Niels E,
Hewitt Michael V,
Penny Alexander,
Jenkinson David S
Publication year - 1989
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740480405
Subject(s) - anthesis , sprayer , crop , agronomy , urea , nitrogen , field experiment , grain yield , yield (engineering) , mathematics , zoology , horticulture , chemistry , biology , cultivar , materials science , organic chemistry , metallurgy
Abstract A new 15 N technique (termed the negative discard method) for measuring recovery of foliar‐applied N by crops in the field is described. 15 N‐labelled fertiliser solution is sprayed on to a small area of crop, using a hand sprayer, while the surrounding area is sprayed with unlabelled N at the same rate. An area considerably larger than that given 15 N is harvested with a small‐plot combine‐harvester, and crop recovery of foliar‐applied N is calculated from the 15 N enrichment of the resulting sample containing a mixture of labelled and unlabelled material. The technique was used to measure recovery of N from 15 N‐labelled urea solution sprayed on to winter wheat ( Triticum aestivum L cv Avalon) at six different times from growth stage 39 (3 weeks before anthesis) to growth stage 73 (2 weeks after anthesis). Each treatment of 40 kg N ha −1 was divided into two equal portions, the second being applied 1–2 days after the first, to minimise the risk of leaf damage. The crop had earlier received 210 kg N ha −1 , as ‘Nitro‐Chalk’, in spring (50 kg ha −1 at growth stage 22 and 160 kg ha −1 at growth stage 31) which was more than sufficient to achieve maximum grain yield. At harvest, 70% of the foliar‐applied N given at anthesis (growth stage 65) was recovered in the above‐ground crop, including 64 % in grain. The proportion of labelled N recovered in the grain (92% of that in the above‐ground crop) was slightly greater than with soil‐applied N given earlier in the growing season. Recovery of foliar‐applied N was slightly less for the earliest (growth stage 39) and latest (growth stage 73) times of spraying: 64% and 58% in above‐ground crop, and 56% and 54% in grain, respectively. All of the foliar applications of 40 kg N ha −1 increased %N in grain to the same extent as an additional 40 kg N ha −1 applied to soil in spring.