Sulfur transformation in 3 soils maintained in a closed incubation system and its availability to plants were investigated using carrier-free35S-SO42- and 35S-labeled ryegrass straw. For carrier-free Na235SO4 treatmen...Sulfur transformation in 3 soils maintained in a closed incubation system and its availability to plants were investigated using carrier-free35S-SO42- and 35S-labeled ryegrass straw. For carrier-free Na235SO4 treatment, 78%, 70% and 64% of 35S applied were found in Ca (H2PO4)2-extractble S fraction 14%, 5% and 7% in slowly soluble inorganic S, 11%, 15% and 18% in C-O-S, 5%, 7% and 6% in C-bonded S, and 5%,7% and 6% in unidentified organic S 120 days after incubation in black soil, cinnamon soil and chestnut soil, respectively. Most of 35S uptake by plants came from extractable 35S42-, and little from C-O-35S and C-bonded 355. In the treatment with 35S-labeled straw, 51%, 46% and 36% of 355 incorporated were found in C a (H2PO4)2 -extractable S fraction) 7%, 6% and 7% in slowly solub ie inorganic S, 13%, 15% and 18% in C-O-S, 8%, 8% and 6% in C-bonded S, and 18%, 25% and 35% in unidentified organic S at the end of incubation in above-mentioned three soils, respectively. Higher availability of C-O-35S, C-bonded 35S and unidentified organic 35S from 35S-labeled straw was observed in 35S-labeled straw treatment compared to carrier-free Na235SO4 treatment.展开更多
Fifteen upland soils collected from the major arable areas in North China were used to assess the availability of soil sulfur (S) to plants in a pot experiment. Soils were extracted with various reagents and the extra...Fifteen upland soils collected from the major arable areas in North China were used to assess the availability of soil sulfur (S) to plants in a pot experiment. Soils were extracted with various reagents and the extractable S was determined using turbidimetric method or inductively coupled plasma atomic emission spectrometry (ICP-AES), respectively. In addition, mineralizable organic S, organic S, N/S ratio, sulfur availability index (SAI) and available sulfur correction value (ASC) in soils were also determined. The S amount extracted by 1.5 g L-1 CaCl2 was nearly equivalent to that by 0.25 mol L-1 KCl (40 ℃), and both of them were slightly smaller than that by 0.01 mol L-1 Ca(H2PO4)2 solution, as measured by turbidimetric method or ICP-AES. The extractable S measured by turbidimetric method was consistently smaller than that by ICP-AES. All methods tested except that for organic S and N/S ratio produced satisfactory results in the regression analyses of the relationships between the amounts of S extracted and plant dry matter weight and S uptake in the pot experiment. In general, 0.01 mol L-1 Ca (H2PO4) 2-extracted S determined by ICP-AES or turbidimetric method and 0.25 mol L-1 KCl(40℃)-extracted S determined by ICP-AES appeared to be the best indicators for evaluation of soil available S.展开更多
文摘Sulfur transformation in 3 soils maintained in a closed incubation system and its availability to plants were investigated using carrier-free35S-SO42- and 35S-labeled ryegrass straw. For carrier-free Na235SO4 treatment, 78%, 70% and 64% of 35S applied were found in Ca (H2PO4)2-extractble S fraction 14%, 5% and 7% in slowly soluble inorganic S, 11%, 15% and 18% in C-O-S, 5%, 7% and 6% in C-bonded S, and 5%,7% and 6% in unidentified organic S 120 days after incubation in black soil, cinnamon soil and chestnut soil, respectively. Most of 35S uptake by plants came from extractable 35S42-, and little from C-O-35S and C-bonded 355. In the treatment with 35S-labeled straw, 51%, 46% and 36% of 355 incorporated were found in C a (H2PO4)2 -extractable S fraction) 7%, 6% and 7% in slowly solub ie inorganic S, 13%, 15% and 18% in C-O-S, 8%, 8% and 6% in C-bonded S, and 18%, 25% and 35% in unidentified organic S at the end of incubation in above-mentioned three soils, respectively. Higher availability of C-O-35S, C-bonded 35S and unidentified organic 35S from 35S-labeled straw was observed in 35S-labeled straw treatment compared to carrier-free Na235SO4 treatment.
文摘Fifteen upland soils collected from the major arable areas in North China were used to assess the availability of soil sulfur (S) to plants in a pot experiment. Soils were extracted with various reagents and the extractable S was determined using turbidimetric method or inductively coupled plasma atomic emission spectrometry (ICP-AES), respectively. In addition, mineralizable organic S, organic S, N/S ratio, sulfur availability index (SAI) and available sulfur correction value (ASC) in soils were also determined. The S amount extracted by 1.5 g L-1 CaCl2 was nearly equivalent to that by 0.25 mol L-1 KCl (40 ℃), and both of them were slightly smaller than that by 0.01 mol L-1 Ca(H2PO4)2 solution, as measured by turbidimetric method or ICP-AES. The extractable S measured by turbidimetric method was consistently smaller than that by ICP-AES. All methods tested except that for organic S and N/S ratio produced satisfactory results in the regression analyses of the relationships between the amounts of S extracted and plant dry matter weight and S uptake in the pot experiment. In general, 0.01 mol L-1 Ca (H2PO4) 2-extracted S determined by ICP-AES or turbidimetric method and 0.25 mol L-1 KCl(40℃)-extracted S determined by ICP-AES appeared to be the best indicators for evaluation of soil available S.
