Plant and Soil 261: 39–46, 2004. © 2004 Kluwer Academic Publishers. Printed in the Netherlands.
39
Effect of manganese spatial distribution in the soil profile on wheat growth in rice–wheat rotation Shihua Lu2,1 , Xuejun Liu1 , Long Li1 , Fusuo Zhang1,4 , Xiangzhong Zeng2 & Caixian Tang3 1 Department of Plant Nutrition, KLPSI-MOE, KLPN-MOA, China Agricultural University,
Beijing 100094, China. of Soils and Fertilzers, Sichuan Academy of Agricultural Sciences, Chengdu, 610066, China. 3 Department of Agricultural Sciences, La Trobe University, Bundoora, Vic. 3086, Australia. 4 Corresponding author∗ 2 Institute
Received 24 December 2002. Accepted in revised form 11 July 2003
Key words: manganese, rice–wheat rotation, soil, spatial distribution, wheat, manganese nutrition
Abstract Manganese (Mn) deficiency in wheat under rice (Oryza sativa L.) and wheat (Triticum aestivum L.) rotation is an important problem in most rice-growing areas in China. A field survey, field trials and a soil column experiment were conducted to determine the relationship between Mn leaching and distribution in soil profiles and paddy rice cultivation and the effects of Mn distribution in soil profiles on wheat growth and its response to Mn fertilization. At five field sites surveyed, total Mn and active Mn concentrations in the topsoil layers under rice–wheat rotations were only 42% and 11%, respectively, of those under systems without paddy rice. Both total and available Mn increased with soil depth in soils with rice–wheat rotations, showing significant spatial variability of Mn in the soil profile. Manganese leaching was the main pathway for Mn loss in coarse-textured soil with high pH, while excessive Mn uptake was the main pathway for Mn loss in clay-textured and acid soil. When Mn was deficient in the topsoil, sufficient Mn in the subsoil contributed to better growth and Mn nutrition of wheat but insufficient Mn in the subsoil resulted in Mn deficiency in wheat.
Introduction Rice–wheat cropping systems are long-established major cereal production systems in China and south Asia (Jiaguo, 2000; Timsina and Connor, 2001). Due to prolonged reducing conditions during the ricegrowing period, downward movement of Mn in the soil occurs (Li, 1992; Lu et al., 1990), with a gradual decrease in Mn concentration, particularly in the surface layer of the soil. Manganese deficiency is common in wheat and other upland crops in rice–wheat rotation systems in China (Liu and Han, 1993; Lu and Zhang, 1997). For example, Hu et al. (1981) and Takkar and Nayyar (1981) found that Mn deficiency in wheat occurred on flood plain soils (Fluvisols) along riversides of the Chengdu Plain and Indo-Gangetic Plains. Manganese fertilization significantly increased ∗ FAX No: +86-10-62891016. E-mail:
[email protected]
grain yields of wheat in their studies (Hu et al., 1981; Takkar and Nayyar, 1981). There have also been reports on the incidence of Mn deficiency in wheat following paddy rice in other regions of China (Chu and Li, 1985; Ma et al., 1985; Yang, 1984) and India (Nayyar et al., 1985). The increasing occurrence of Mn deficiency and decline in wheat grain yield at many sites without Mn application stimulated studies to develop techniques for efficient management of this problem. Various Mn fertilizers (Mn salts, chelates such as Mn-EDTA and preparations consisting of mixtures of micronutrients) and various application methods (soil, foliar and seed application) have been evaluated for their efficiency in correcting Mn deficiency in wheat (Liu et al., 2001; Nayyar et al., 1985, 2001). Most studies have sought to overcome the deficiency of this micronutrient through the application of Mn fertilizers. However, the role of the spatial distribution of Mn in soil profile in Mn the nutrition
40 of wheat has seldom been considered. The objectives of this study were to: (1) determine Mn mobilization and distribution in the soil profile under rice–wheat rotation, and (2) assess the relationship between Mn spatial distribution and Mn nutrition of wheat following rice. This paper reports a field survey on Mn in soil profiles along with field trials in which the response of wheat crops to application of Mn fertilizers was examined in Sichuan Province, one of the most important rice production regions in China. Leaching losses of Mn were also studied in a soil column experiment.
Materials and methods Field surveys Soil samples were collected from five sites under rice–wheat rotation and the adjacent cropping system with upland crops only on the same soil types: Fluventic Eutrochrepts (Soil Survey Staff, 1975). The sampling sites were Tianfu town in Wenjiang County (30◦ 42 N, 103◦ 50 E), Guihu town in Xindu County (30◦ 54 N, 103◦ 58 E), Fujiang town in Mianyang city (31◦ 12 N, 104◦ 09 E), Anshong town (30◦ 56 N, 103◦ 55 E) and Tianping town (30◦ 53 N, 103◦ 57 E) in Shimian County all on Chengdu Plain in Sichuan province, southwest China. Soil column experiment A PVC tube, 11 cm internal diameter and 100 cm long, was packed with either Grey fluvisol or Grey-brown fluvisol soil. The soils were collected from Tianfu town in Wenjiang County and Guihu town in Xindu County. Selected properties of the soils are shown in Table 1. A PVC conical funnel was placed at the bottom of each column where the leachate was collected. About 0.5 kg of gravel was placed at the bottom of each column to aid drainage. The soils were sieved through a 5-mm sieve and packed to a bulk density of 1.2 g cm−3 . Basal fertilizers (0.5 g urea, 0.3 g monoammonium phosphate, 0.3 g potassium chloride and 10 g dry matter pig manure) were applied to the top 20 cm of each column and mixed thoroughly with the soil. The types and application rates of fertilizers used were those typical of local farming practice. To simulate field conditions, two water treatments with three replicates were imposed: (1) flooding, retaining 2–3 cm depth free water layer above the soil surface
Figure 1. Effect of water status on Mn concentration in leachates of Grey fluvisol (A) and Grey-brown fluvisol (B). Bar = S.E. (Standard Error).
with distilled water; (2) wetting, supplying water to water holding capacity with distilled water. The rice used was hybridized cultivar ‘Shanyou 63’. Eight pregerminated seeds of hybrid rice were sown in each column and thinned to four plants 7 days after sowing. Water levels in the column were adjusted daily. During the experiment the volumes of leachate were recorded regularly. Manganese concentrations in the leachates were measured by atomic absorption spectrophotometry (AAS, model: Hitachi-Z8000, Japan) and the amounts of Mn leaching were calculated by multiplying the Mn concentration by the volume of leachate. The above-ground parts of the plants were harvested after growth for 80 days. Shoot dry matter and Mn concentrations were recorded or analyzed according to the methods in the Measurement section. Field trials The field trials were conducted to assess wheat response to Mn fertilization at four sites located at Tianfu town in Wenjiang county. The soils were sandy
41 Table 1. Some properties of the two soils in the soil column experiment Soil supplied
Texture
pH (H2 O)
O.M.∗ g kg−1
Total-Mn mg kg−1
Active-Mn# mg kg−1
Exc-Mn$ mg kg−1
DTPA-Mn& mg kg−1
Grey fluvisol Grey-brown fluvisol
Sandy loam Medium loam
8.1 5.8
18.9 26.4
534 615
112 213
4.7 27.0
7.7 50.9
∗ O.M. – organic matter. # Active-Mn, extracted by 1 mol L−1 NH OAC + 2 g L−1 hydroquinone. 4 $ Exc-Mn, exchangeable Mn, extracted by 1 mol L−1 NH OAc (pH 7.0). 4 & DTPA-Mn, extracted by 0.005 mol L−1 DTPA (pH 7.3).
Table 2. Some properties of soils in the field trials Fields
Soil type
Texture
pH (H2 O)
O.M.∗ g kg−1
Total-Mn mg kg−1
Active-Mn# mg kg−1
Exc-Mn$ mg kg−1
DTPA-Mn& mg kg−1
1 2 3 4
Grey fluvisol Grey fluvisol Grey fluvisol Grey fluvisol
Sandy loam Sandy loam Sandy loam Course sandy loam
7.8 8.1 7.8 7.7
23.1 19.7 19.9 21.5
423 468 432 385
7.1 9.1 10.3 12.1
0.68 0.35 0.80 0.22
1.21 1.08 1.26 0.97
∗ O.M. – organic matter. # Active Mn, extracted by 1 mol L−1 NH OAc + 2 g L−1 hydroquinone. 4 $ Exchangable Mn, extracted by 1 mol L−1 NH OAc (pH 7.0). 4 & Available Mn, extracted by 0.005 mol L−1 DTPA (pH 7.3).
Table 3. The difference in manganese distribution in soil profile between the rice–wheat rotation and the upland soil Site
Soil depth (cm)
DTPA-Mn (mg kg−1 ) R–Wa Non R–W S
1b
0–20 20–40 40–60 0–20 20–40 40–60 0–16 16–21 21–55 0–20 20–40 40–60 0–20 20–40 40–60
3.3 6.8 11.1 6.0 30.7 11.6 16.3 20.2 13.6 1.2 3.8 17.8 6.1 5.6 22.3
2
3
4
5
7.7 6.2 6.1 50.9 39.6 20.4 5.2 3.8 3.8 7.8 6.6 7.8 21.0 16.2 16.9
∗
NSc ∗ ∗∗
NS ∗ ∗ ∗∗ ∗ ∗
NS ∗ ∗∗ ∗
NS
Active Mn (mg kg−1 ) R–W Non R–W S 20 75 144 15 512 294 76 141 388 19 62 681 20 29 632
112 118 125 210 195 163 266 268 215 185 171 161 541 564 577
∗∗ ∗
NS ∗∗ ∗∗ ∗ ∗∗ ∗ ∗ ∗∗ ∗ ∗∗ ∗∗ ∗∗
NS
Total Mn (mg kg−1 ) R–W Non R–W S 267 380 426 207 624 533 259 329 656 426 509 1539 368 388 1432
515 495 508 342 434 401 585 610 634 774 709 616 1446 1454 1455
∗ ∗
NS ∗ ∗ ∗ ∗∗ ∗∗
NS ∗∗ ∗ ∗∗ ∗∗ ∗∗
NS
a R–W, Non R–W, and S refer rice–wheat rotation, upland cropping system without rice, and difference signific-
ance, respectively. b Sites 1, 2, 3, 4 and 5 refer to Tianfu town of Wenjiang county, Guihu town of Xindu county, Fujiang town of Mianyang city, Anshun town of Shimian county, and Tianping town of Shimian county, respectively. c NS, ∗ and ∗∗ refer not significant, significant at 5 and 1% levels by the t-test, respectively.
42 Table 4. Mn leaching, shoot biomass production and Mn uptake by rice under irrigation treatments in Grey fluvisol and Grey-brown fluvisol Soil supplied
Treatment
Grey fluvisol (GF)
Flooding (F) Wetting (W) Grey-brown Flooding (F) Fluvisol (GBF) Wetting (W) Significance of treatment GF vs GBF F vs W – F vs W at GF – F vs W at GBF
Mn leaching (mg col.−1 )
Shoot biomass (g col.−1 )
Mn conc. in shoot (mg kg−1 )
Mn uptake by rice (mg col.−1 )
34.7 5.2 14.4 0.5
14.9 12.7 35.7 34.4
281 67 680 110
4.2 0.9 24.5 3.8
∗∗
∗∗
∗∗
NS NS NS
∗∗
NS
∗∗
∗∗
∗∗
∗∗
∗
NS
∗∗
∗∗
Statistical analysis was performed by the split-plot model and multiple comparison, ∗ p < 0.05, ∗∗ p < 0.01, NS, not significant; col. is the abbreviation of column. Table 5. Severity of Mn deficiency in wheat at different growth stages Date
Site 1 −Mn +Mn
Site 2 −Mn +Mn
Site 3a −Mn +Mn
Site 3b −Mn +Mn
Site 4 −Mn +Mn
10 Dec 12 Dec 19 Dec 26 Dec 09 Jan 19 Jan 02 Feb 25 Feb 08 Mar 15 Mar 24 Mar 04 Apr
0 + ++ +++ +++ +++ +++ +++ +++ ++ ++ +
0 0 ++ ++ +++ +++ ++ + + 0+ 0+ 0
0 + ++ +++ +++ +++ +++ ++ +++ ++ ++ +
0 0 0 + + + 0+ 0 0 0 0 0
0 0 0 0 0 + 0+ 0+ 0+ 0 0 0
0 0+ 0 0 0 0 0 0 + 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 + 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0
“0, 0+ , +, ++ and +++” refer to none, slight, low, intermediate and serious symptoms of Mn deficiency in wheat, respectively.
loam fluvisols and some selected properties of these soils were listed in Table 2. There were two treatments, application of Mn (+Mn) and without Mn (−Mn) as control with four replications. Manganese was applied by mixing seeds with MnSO4 (at the rate of 6 g MnSO4 per kg seeds) at sowing and thereafter foliar spraying Mn solution (2 g L−1 MnSO4 solution and 750 L ha−1 each time). The foliar spray was applied on 5 December, 15 December, 26 December 1996, and 2 February 1997, for sites 1 and 2; and on 4 December, 12 December and 26 December, 1996, for sites 3 and 4. Nitrogen fertilizer was applied at 155 kg N ha−1 as urea, P fertilizer at 32 kg P ha−1 as superphosphate, and K fertilizer at 68 kg K ha−1 as potassium
chloride. Plot size was 15 m2 . Seeds of wheat cultivar ‘Mianyang 11’ were sown on 11 November 1996. The dynamics of Mn deficiency symptoms of wheat were recorded from 10 December 1996 to 4 April 1997. On days 45 and 120 after sowing, plant samples were collected to determine dry matter and Mn concentrations. At maturity, the grain yield of each plot was recorded. Soil samples were collected at different depths for determination of soil pH and the concentrations of active Mn and total Mn. Measurements Shoot dry matter was recorded by oven drying at 65 ◦ C for 48 h (Shi, 1990). Manganese concentrations
43 Table 6. Manganese distribution in the soil profiles at different field sites Sites
Soil layer (cm)
Soil texture
pH (H2 O)
1
0–12 12–21 21–30 30–60
2
0–14 14–21 21–40
3a
0–12 12–19 19–60
3b
0–14 14–23 23–68
4
0–16 16–26 26–60
Light loam Light loam Sand Coarse sand LSD0.05 Light loam Light loam Light loam LSD0.05 Light loam Light loam Coarse sand LSD0.05 Light loam Light loam Medium loam LSD0.05 Medium loam Medium loam Light loam LSD0.05
7.8 7.8 8.1 8.3 0.42 7.9 8.1 8.2 NS 8.0 8.0 8.3 NS 8.0 8.1 8.3 NS 7.9 8.0 8.3 0.35
Active Mn∗ (mg kg−1 ) 7.8 9.9 6.7 11.6 NS# 9.4 21.4 39.5 15.8 6.8 7.9 7.4 NS 13.4 15.4 50.7 22.9 11.1 15.3 461 45.2
Total Mn (mg kg−1 ) 423 438 475 410 NS 468 513 573 95.0 439 449 436 NS 424 434 532 87.5 385 422 985 125
∗ Mn extracted by 1 mol L−1 NH OAc + 2 g L−1 hydroquinone. 4 # NS – not significant.
in the whole shoots were measured by digestion in HClO4 –HNO3 and AAS (Shi, 1990). Total Mn uptake was calculated by multiplying shoot Mn concentration with shoot dry mater. Total Mn in soil was determined by AAS after digesting the soil in HNO3 –HClO4 –HF solution (Sparks et al., 1996). Active Mn was extracted in 1 mol L−1 of neutral NH4 OAc + 2 g L−1 hydroquinone (Shi, 1990), exchangeable Mn (Exc-Mn) extracted in 1 mol L−1 neutral NH4 OAc (Shi, 1990) and available Mn (DPTA-Mn) extracted by 0.005 mol L−1 DTPA at pH 7.3 (Shi, 1990). The above Mn forms were all determined by AAS. Other soil properties were determined by conventional methods (Sparks et al., 1996). Results Field survey There were significant differences in Mn concentrations in the surface 20 cm of the soil profile between the rice–wheat rotation (R–W) and the upland cropping system (Non R–W) (Table 3). The average con-
centrations of total Mn and active Mn in soils under rice–wheat rotation were only 42% and 11%, respectively, of those in soils under the upland cropping system (Table 3), indicating that soil active Mn (easily reducible Mn) lost significantly as compared with that in the upland soils. There were also significant differences in Mn distribution in the soil profile between rice–wheat rotation and the upland cropping systems. Different forms of Mn (e.g., exchangeable Mn, DTPAMn, active Mn, and total Mn) were evenly distributed in different layers of upland soils. In contrast, in the rice–wheat rotation, the Mn content in the same form was much higher in the subsoil than in the topsoil (Table 3). This is in accordance with the observation that the Mn background value in the 0–20-cm soil layer was less than that in the 20–40-cm soil layer in a paddy soil located in western Sichuan (Xia, 1987). Under the rice–wheat rotation, the ratios of active Mn to total Mn were 5–29% in the 0–20-cm soil layer, 8–82% in the 20–40-cm soil layer, and 44–55% in the 40–60-cm soil layer (Table 3). Therefore, the decrease in active Mn in the 0–20-cm soil layer was related to the reduction of Mn4+ and Mn3+ to Mn2+ in the 0–
44 Table 7. Shoot Mn concentration and yield response of wheat to Mn fertilization Sites
Mn concentration (mg kg−1 ) Day 45 Day 120 Significance
Grain yield (kg ha−1 ) −Mn +Mn Significance
1 2 3a 3b 4
22.9 21.5 22.4 23.2 26.2
1344 2709 2481 4341 4929
24.5 31.3 23.8 44.2 69.5
NS ∗
NS ∗∗ ∗∗
3399 3339 3780 4209 5043
∗∗ ∗ ∗
NS NS
Statistical analysis was performed using the split-plot model and multiple comparison, ∗ p < 0.05, ∗∗ p < 0.01, NS, not significant.
20-cm soil layer and subsequent leaching of Mn2+ to the subsoil during flooding for rice cultivation. Column leaching experiment Manganese concentration in the leachates from the soil columns was very low in the first 2 weeks and no statistical difference was observed between the flooding and the wetting treatments. After the first 2 weeks, however, the amount of Mn leached from soil columns was significantly higher in the flooding than in the wetting treatment for the Grey fluvisol (Figure 1a). A similar trend was found for the Grey-brown fluvisol during the period from day 14 to day 47 (Figure 1b). Total Mn leached from the 1-m soil column, Mn concentration in rice plants, and Mn uptake by rice were all significantly higher in the flooding treatment than in the wetting treatment (Table 4). These results indicate that both the Mn leaching from the soil profile and the Mn uptake by rice were significantly enhanced by flooding, as compared with wetting. Further, the soils differed in Mn leaching with Mn leaching lasting longer in the Grey fluvisol (Figure 1). Mn distribution in the soil profile and growth of wheat The soils in the field investigation were all Mndeficient based on their available Mn content (Table 2) and the critical level for Mn deficiency in soils (Liu and Zhu, 1980; Yu and Peng, 1984). However, the severity of Mn deficiency differed greatly among the field sites (Table 5). This difference could not be explained by the Mn concentration in surface soils because there was no significant difference in Mn content in this soil layer (Table 2). At Site 3, some patches of the paddock (Site 3a) showed serious Mn deficiency in wheat, whereas other patches (Site 3b) produced only slight Mn deficiency in wheat (Table 5). At Sites 1 and 3a, there existed a sandy layer below 20 cm in the soil
profile, and the Mn concentrations in the subsoil layer were not drastically different from those in the topsoil layer (Table 6), where Mn deficiency symptoms appeared earlier and lasted longer (Table 5). Significant responses to Mn fertilization were also observed at Sites 1 and 3a (Table 7). At Site 2, however, as Mn concentrations in the subsoil layer was higher than that in the topsoil layer (Table 6), where serious Mn deficiency in wheat occurred in January was alleviated in February, and Mn concentration in the plants increased to 31 mg kg−1 in March from 22 mg kg−1 at the early stage. Thus the magnitude of yield increase by Mn fertilization was lower at Site 2 than at Sites 1 and 3a (Table 7). Furthermore, at sites 3b and 4, Mn concentration in the subsoil was significantly higher than in the topsoil (Table 6). As a result, only slight Mn deficiency symptoms occurred from early tillering to the stem elongation stage (Table 5); Mn concentration in the plants increased significantly and Mn fertilization did not enhance yield of wheat (Table 7). Discussion Soil Mn, especially the easily reducible form, is strongly influenced by the soil Eh (redox potential) value. The threshold Eh value for the total soil (watersoluble + exchangeable) iron (Fe) and Mn was about −150 to 0 mV (Atta et al., 1996; Xiang and Banin, 1996). Our results showed significant Mn leaching under rice–wheat rotation that led to a lower Mn concentration in the soil profile. Flooding of paddy soils decreases soil Eh, and thus resulted in Mn oxides being reduced and becoming water-soluble, which causes Mn leaching with water (Yang et al., 1987; Zhang and Gong, 1993). The residual Mn decreases when the easily reducible Mn increases with decreasing soil Eh value and vice versa (Atta et al., 1996). Under controlled conditions, the Eh and pH values
45 determine the concentrations of water-soluble and exchangeable Mn (Gotoh and Patrick, 1972). The residual Mn fraction is also affected by the addition of organic matter as a consequence of the effect on the other fractions (Atta et al., 1996). Khan and Fenton (1996) also found that the contents of Fe-d and Mn-d (citrate-bicarbonate-dithionite-extractable Fe and Mn) in soil horizons decreased with permanent water saturation and presence of gray matrices. Therefore, the spatial variability in Mn distribution in the soil profile found in this study could be partly caused by movement of Mn from the topsoil to subsoils (Gotoh and Patrick, 1972; Sharma et al., 2000; Xu, 1989). This study also showed that Mn uptake by rice increased significantly under flooding. Similar results were also observed in another study (Lu and Zhang, 1997). It appears that the increased Mn uptake by rice was another cause of Mn spatial distribution in soil profiles, which had not been previously determined with a long-term trial. The relative contribution of Mn leaching and plant Mn uptake to soil Mn spatial distribution was dependent on several factors including soil type and rice variety. For example, Mn leaching was the main pathway of Mn spatial distribution on the coarse-textured and high-pH soil (Grey fluvisol). In contrast, Mn uptake by rice was the main pathway of the Mn spatial distribution on the clay-textured and low-pH soil (Grey-brown fluvisol). Manganese leaching in soil is enhanced as the wheat-rice rotation continues (Liu, 1997). What concerns us is how to slow down the leaching loss of Mn. Our results show that the amounts of soil Mn lost in the wetting treatment were only 11% (in the Greybrown fluvisol) to 16% (in the Grey fluvisol) those in the flooding treatment. Thus, in order to minimise the soil Mn loss, it is recommended to change the cropping pattern of traditional flooding cultivation into the non-flooded cultivation (Liu et al., 2003). A large biomass of crop roots can be distributed in the subsoils, contributing greatly to nutrient acquisition (Barber, 1984). The contributions to plant nutrition of N, P and K in subsoils have been extensively investigated (Kuhlmann, 1990; Kuhlmann and Banmgartel, 1991; Wermann and Scharpf, 1986). Approximately 37–85% of the P uptake by wheat was derived from the subsoil (Kuhlmann and Banmgartel, 1991) and was 9–70% for K (Kuhlmann, 1990). Our present study shows that an adequate Mn concentration in the subsoil could significantly improve Mn nutrition in wheat. In contrast, when Mn was limiting in the subsoil, severe Mn deficiency symptoms in
wheat occurred and there was a yield response to Mn fertilization. Clearly, the spatial distribution or variability of Mn in the soil profile could play an important role in Mn nutrition of wheat. In this respect, proper management of subsoils that favors root growth could mitigate Mn deficiency in wheat under the rice–wheat rotation. However, further studies are required to determine the contribution of Mn in the subsoil to the improvement of wheat Mn nutrition under rice–wheat rotation.
Acknowledgements We are grateful for generous financial support from the Major State Basic Research Development Program of the People’s Republic of China (No. G1999011707), the Major Research Program of the Chinese Ministry of Education (No. 0112), and the National Natural Science Foundation of China (No. 49801013, No. 39600089). We are also grateful to Professor Hans Lambers at the University of Western Australia and Dr Peter Christie at Queen’s University Belfast, UK, for their valuable suggestions and comments on the manuscript.
References Atta S K, Mohammed S A, Vancleemput O and Zayed A 1996 Transformations of iron and manganese under controlled Eh, EhpH conditions and addition of organic matter. Soil Technol. 9, 223–237. Barber S A (Eds) 1984 Soil Nutrient Bioavailability: A Mechanistic Approach. John Wiley & Sons, New York. Chu T D and Li X P 1985 Wheat manganese deficiency occurred in calcareous soils in Northern China. Soils Fertil. 4, 3 (in Chinese). Gotoh S and Patrick W H 1972 Transformation of manganese in waterlogged soil as affected by redox potential and pH. Soil Sci. Soc. Am. Proc. 38, 66–71. Hu S N, Hua W Q, Lu M and Jiang Y W 1981 Study on wheat manganese deficiency with manganese fertilizer experiment on calcareous soils in Wenjiang county. Soils 13, 100–103 (in Chinese). Jiaguo Z 2000 Rice–wheat cropping system in China. In Soil and Crop Management Practices for Enhanced Productivity of the Rice–Wheat Cropping System in Sichuan Province of China. Rice–Wheat Consortium Paper Ser. 9, Eds. Hobbs P R and Gupta R K. pp. 1–10. Rice–Wheat Consortium for the Indo-Gangetic Plains, New Delhi. Khan F A and Fenton T E 1996 Secondary iron and manganese distributions and aquic conditions in a mollisol catena of central Iowa. Soil Sci. Soc. Am. J. 60, 546–551. Kuhlmann H 1990 Importance of subsoil for the K nutrition of crops. Plant Soil 127, 129–136. Kuhlmann H and Baumgartel G 1991 Potential importance of subsoil for P and Mg nutrition of wheat. Plant Soil 137, 259–266.
46 Li Q K (Eds.) 1992 Paddy Soils in China. Chinese Scientific Press, Beijing. Liu X J 1997 Mechanisms and prevention strategies of manganese deficiency in wheat on soils under rice–wheat rotation in Sichuan province. Ph.D. Thesis, China Agricultural University, Beijing (in Chinese). Liu X J, Zeng X Z, Lu S H and Zhang F S 2001 Effects of Mn application periods on Mn nutrition and grain yield of different wheat genotypes. Southwest China J. Agric. Sci. 14, 39–43 (in Chinese). Liu X J, Wang J C, Lu S H, Zhang F S, Zeng X Z, Ai Y W, Peng S B and Christie P 2003 Effects of non-flooded mulching cultivation on crop yield, nutrient uptake and nutrient balance in rice–wheat cropping systems. Field Crops Res. (in press). Liu X H and Han X L (Eds.) 1993 Cropping Systems in China. Agricultural Press, Beijing (in Chinese). Liu Z and Zhu Q Q (Eds.) 1980 Symposium on Micro-elements Research Communication Meeting in Academia Sinica. Scientific Press, Beijing (in Chinese). Lu S H, Xu Y X and Hu S N 1990 Features of manganese of paddy soil conditions of manganese deficiency on wheat. Southwest China J. Agric. Sci. 3, 87–91 (in Chinese). Lu S H and Zhang F S 1997 Review and outlook of ten years research on crop Mn nutrition in soils with upland-paddy rotation. Soil Bull. 12, 1–7 (in Chinese). Ma G R, Shi W Y and Yin X X 1985 Investigation of manganese deficiency symposium in wheat. Zhejiang Agric. Sci. 2, 85–87 (in Chinese). Nayyar V K, Sadana U S and Takkar T N 1985 Methods and rates of application of Mn and its critical levels for wheat following rice on coarse textured soils. Fertil. Res. 8, 173–178. Nayyar V K, Arora C L and Kataki P K 2001 Management of soil micronutrient deficiencies in the rice–wheat cropping system. In The Rice–Wheat Cropping System of South Asia: Efficient Production Management. Ed. Palit K. Kataki. pp. 87–131. J. Crop Production, Vol. 4, No. 1. Food Products Press, an imprint of The Haworth Press, Inc., New York. Sharma B D, Mukhopadhyay S S, Sidhu P S and Katyal J C 2000 Pedospheric attributes in distribution of total and DTPA-extractable
Zn, Cu, Mn and Fe in Indo-Gangetic plains. Geoderma 96, 131– 151. Shi R H (Eds) 1990 Soil and Plant Analysis. 2nd Edition. Agricultural Press, Beijing (in Chinese). Soil Survey Staff 1975 Soil Taxonomy. U.S. Dept. Agriculture Handbook No. 436, Washington, DC. Sparks D L, Page A L, Helmke P A, Loeppert R H, Soltanpour P N, Tabatabai M A, Johnston C T and Summer M E (Eds.) 1996 Methods of Soil Analysis. Part 3. Chemical Methods, SSSA Book Ser. No.5; SSSA: Madison, WI. Takkar P N and Nayyar V K 1981 Preliminary filed observation of manganese deficiency in wheat and berseem. Fertil. News 26, 22–23, 33. Timsina J and Connor D J 2001 Productivity and management of rice–wheat cropping systems: Issues and challenges. Field Crops Res. 69, 93–132. Wehrmann S J and Scharpf H C 1986 The Nmin -method – an aid to integrating various objectives of nitrogen fertilization. Z. Pflanzenernaehr. Bodenkd. 149, 428–440. Xia Z L (Eds) 1987 Background Content of Soil Elements and its Research Methods. Meteorological Press, Beijing (in Chinese). Xiang H F and Banin A 1996 Solid-phase manganese fractionation changes in saturated arid-zone soils – pathways and kinetics. Soil Sci. Soc. Am. J. 60, 1072–1080. Xu Q 1989 Research progress on paddy soils. Soils 21, 192–195 (in Chinese). Yang Z 1984 Soil manganese deficiency and wheat color-leaf and death of seedling. Yunnan Agric. Sci. Technol. 6, 23–25 (in Chinese). Yang L Z, Xu Q and Xiong Y 1987 Effect of soil water condition on the migration of mineral elements and the crop growth in paddy soils derived from red earth. Acta Pedolog. Sinica 24, 199–209 (in Chinese). Yu C Z and Peng L 1984 Evaluation on soil available manganese (DTPA-Mn) and discussion on its critical value. Acta Pedol. Sinica 21, 277–283 (in Chinese). Zhang G L and Gong Z T 1993 Geochemical features of the migration of mineral elements in soils under waterlogging condition. Acta Pedol. Sinica 30, 355–364 (in Chinese).
