Availability of Subsoil Sulphates to Barley and Rapeseed

Abstract

Increased use of sulphur (S) fertilizers in southern Alberta led to a series of field and phytotron experiments to investigate the importance of S fertilizers and the role of subsoil reserves of sulphate sulphur (SO4-S) for barley (Hordeum vulgare) and rapeseed (Brassica napus). Two types of experiments were conducted. In the field-plot studies, barley was grown on dryland soils low in surface SO4-S but underlain by subsoil high in SO4-S. Neither elemental nor SO4 forms of S significantly increased barley yields in a series of 10 experiments on those soils. The comparisons were made at three levels of N fertilizers. In a series of lysimeter studies, three successive crops were grown in soil low in inorganic S (2.0 μg SO4-S∙g−1), or soil supplemented with 25 μg 35SO4-S∙g−1 soil at specified depths in the lysimeters. Barley was adequately supplied with S from SO4-S at a depth of 54–72 cm. It obtained 55% of its S from a high SO4-S (25 μg∙g−1) layer of soil at that depth, although 40 days growth were required before the S was effectively utilized. Five times as much S was taken up by the barley when the entire soil received an additional 25 μg SO4-S∙g−1 as when only the 54- to 72-cm depth was supplemented; however, the yields were unaffected. Most of the excess S was retained in the straw. Rapeseed took up an increasing amount of SO4-S as the proportion of the lysimeters that initially contained SO4-S was increased. Rapeseed was also able to utilize SO4-S from a depth of 54–72 cm. Rapeseed showed deficiency symptoms when most of the added and soil reserves of S had been depleted by previous crops; its growth habit became indeterminate and seeds did not develop. Although total dry matter yield was not greatly affected, seed yield was markedly reduced in S-deficient rapeseed. Rapeseed took up 10 times as much S as did barley when the S supply was just adequate for seed production. Although rapeseed had a much higher S requirement than barley, both crops were adequately supplied by subsoil reserves of SO4-S under the field and controlled environment conditions studied. The studies suggest that fertilizer recommendations should be based on soil analysis to a depth of at least 60 cm. Key words: Sulphur fertilizer, sulphates, 35S, barley, rapeseed, nutrient uptake

Influence of six successive annual applications of sulphur fertilizers on wheat in a wheat–canola rotation on a sulphur deficient soil

“…Similarly, in our study, wheat was less sensitive to S deficiency, and frequency and magnitude of response to S fertilization were lower than canola grown in the same companion experiment in a rotation with wheat (Malhi et al 2007). This was most likely due to the fact that cereals require less S than oilseed crops for optimum yield (Wetter et al 1970;Bole and Pittman 1984). With the exception of the first year, yield responses of wheat to elemental S fertilizer with six annual applications were relatively more frequent in this study than in a previous 4-yr study with wheat in northeastern Saskatchewan (Malhi 2006).…”

“…Although cereals require less S than oilseed crops (Bole and Pittman 1984), S fertilization is needed for optimum growth and yield of cereals on severely S-deficient soils (Nyborg et al 1974).…”

Fertility management in canola production

“…Rape requires about 1.5 kg of S to grow 100 kgof seed (Nyborget al 1974), so a 2000 kg ha-rcrop would require approximately 30 kg S ha -'. To produce adequate seed yields, rape needs between 3 and l0 times as much S as barley (Hamm 1967;Bole and Pittman 1984) and therefore response to application of S often occurs in rapeseed on sites where no S response occurs in cereals (Hamm 1967;Nyborg et al 1914).…”

Fertilizer response of barley grain in south and central Alberta

“…Prairie soils often contain adequate levels of plant-available K for cereal growth, but significant increases in barley yield were reported after application of K fertilizer in central Alberta soils with low levels of exchangeable K (Dick et al 1985;McKenzie et al 2004). Barley response to S fertilization has been observed in central and northern Alberta (Nyborg 1968), but it occurs less frequently in south Alberta due to the presence of sulphates in irrigation water and subsoils (Bole and Pittman 1984). Although micronutrient responses are relatively rare in Alberta, copper and zinc deficiencies may occur (McKenzie 2001).…”