Sulfur Diagnostic Criteria as Affected by Age and Defoliation of Subclover

Abstract

Sulfur deficiencies are widespread in California annual grasslands and in other areas of the world where subclover (Trifolium subterraneum L.) is an important legume. Intensive grazing is often practiced where subclover is grown. Therefore, to determine the need for S fertilization it is important to know how defoliation and plant age influence the diagnostic tissue tests used to assay subclover S status. Subclover was grown on S−deficient soil (Josephine, fine−loamy, mixed mesic, Typic Haplozerults) with six levels of applied S and four clipping treatments in a greenhouse. Four criteria for assaying S status were used: total S, sulfate S, sulfate S/total S ratio, and N/S ratio in the three youngest fully expanded leaves required to give 90% of maximum yield (critical levels based on Mitscherlich functions). The critical levels of sulfate S/total S and N/S ratios were the most stable over plant age and clipping frequency. Both assays accounted for about three−quarters of the variation on the average. The critical levels of total S and sulfate S although associated with over 90% of the variation were not stable individually, decreasing from 0.20 to 0.08% S and from 220 to 140 pprn sulfate S at 60 and 133 days from planting, respectively. Clipping frequency caused considerable variation in the critical levels for total S and sulfate S assays, making them more difficult to interpret than the sulfate S/total S and N/S ratio assays. It was concluded that the sulfate S/total S ratio has some advantages over the other assays, such as stability through the growing season, being little affected by defoliation, and resulting from a single analytical regime.

PHOSPHORUS-MOLYBDENUM RELATIONSHIP IN SOIL AND RED CLOVER (Trifolium pratense L.) ON AN ACID ANDISOL

“…These results are in agree with previous reports (Vistoso, 2005;Mora et al, 2002). Also and as expected, we found that the application of increasing P rates increased steadily shoot P concentration according to Jones et al (1980) and Basak et al (1982). Shoot P concentrations were positively correlated (r = 0.844, P < 0.01) with soil available P levels (Figure 3b).…”

“…In this hand, Jones et al (1980) reported normal values of shoot concentration of P between 2.0 to 2.8 g kg -1 DM, whereas Bolland et al (1995) indicated normal levels ranged from 2.0 to 3.0 g kg -1 DM. These P concentrations values are similar to those reported as normal P shoot contents in others legumes forage, such as subterraneum clover (Trifolium subterraneum L.) with 2.25 g kg -1 DW (Drlica and Jackson, 1979) and white clover (Trifolium repens L.) with 3.50 g kg -1 DM (Sinclair et al, 1997).…”

Sulfur deficiency of rice plants in the Lower Volta area, Ghana

“…Regarding the sulfur status, the level of NPK +0.3S (0.02 g S kg-I) was probably maintained in a potential shortage of sulfur, although dry matter production was apparently as large as that in the case of NPK +O.4S or NPK +0.5S (Table 3) in the present experiment. The ratio is consistent with that reported by Jones et al (1980), Smith and Dolby (1977), and Spencer and Freney (1980): 0.08 to 0.15 for wheat, Panicum maximum, and Trifolium subterraneum. However, it is not effective in the assessment based on the sulfate concentration per se, since the two variables behaved almost identically among the treatments (Tables 5-7).…”

“…This is occasionally observed when there is an extreme deficiency of various nutrients in a wide range of crops. The occurrence of this phenomenon is somewhat frequent when the response curve is related to sulfur nutrition either for the total-S or sulfate concentration both in rice and upland crops (Jones and Quagliato 1970;Osiname and Kang 1975;Smith and Dolby 1977;Jones et al 1980). The response curve of sulfate to shoot dry weight observed in Exp.…”

Sulfur-supplying capacity of soils and critical sulfur values of forage crops

“…More recently the SQ-S/total-S ratio had been (SPENCER and FRENEY 1980), and subclover (JONES et al 1980).…”