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Soybean Irrigation Serially Timed During Stages R1 to R6. II. Yield Component Responses 1
Author(s) -
Kadhem F. A.,
Specht J. E.,
Williams J. H.
Publication year - 1985
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/agronj1985.00021962007700020027x
Subject(s) - irrigation , cultivar , yield (engineering) , biology , horticulture , mathematics , agronomy , physics , thermodynamics
Soybean [ Glycine max (L.) Merr.] seed yield components are established and fixed in a temporally ordered sequence during stages R1 to R6. To determine the effect of irrigation timing during R1 to R6 on these traits, we examined the seed yield component responses of 16 soybean cultivars to nine irrigation treatments in a 3‐year experiment. Treatments T 1 thru T 7 consisted of only a single irrigation coinciding with the average R stages 1.1, 2.5, 3.7, 4.7, 5.6, 5.9, and 6.4, respectively. ‘Check’ treatments included T 0 , which was not irrigated, and T 8 which received seven total irrigations coincident with those for T 0 and T 7 . Averaged over cultivars and years, the mean number of seeds/plant were: T 0 : 87f, T 1 : 121a, T 2 : 111bc, T 3 : 115ab, T 4 : 105cd, T 5 : 99def, T 6 : 102de, T 7 : 95ef, and T 8 : 122a. T 0 and T 8 thus established the minimum and maximum ‘limits’ in the seeds/plant response, respectively, with declining responses as irrigation was delayed from T 1 to T 7 . The 100‐seed weight (g) means were: T 0 : 19.1b, T 1 : 17.8c, T 2 : 17.8c, T 3 : 18.3c, T 4 : 20.3a, T 5 : 20.4a, T 6 : 19.8ab, T 7 : 20.3a, and T 8 : 18.3c. Seed size for T 8 was thus smaller than T 0 . The T 4 thru T 7 responses were significantly greater than T 0 , while the T 1 thru T 3 responses were significantly less than T 0 . Average seed yields were greatest for the T 3 and T 4 treatments, although for determinate cultivars, T 8 also resulted in high yields. Only minimal changes in seed number and size were affected by irrigation in the determinate cultivars (in contrast to indeterminates), which may have accounted for the greater yield responsiveness of determinate cultivars to irrigation. Based on both the seed yield and yield component data, it would appear that stage R3.5 to R4.5 represents the reproductive period in soybeans most responsive to irrigation.