1985; Farina and Channon 1988; Sumner and Carter 1988; Shainberg et al. ...... (H. Daniel, personal communication) between control and gypsum plots at the.
Amelioration of Subsurface Subsurface Acidity in Sandy Soils Soils Amelioration Regions. I. Responses Responses of Wheat in Low Rainfall Regions. and Lupins to Surface-applied Surface-applied Gypsum Gypsum and Lime C. McLay, C. D. A. M c~
P. Ritchie Ritchie *G.? S. S. ~ P.
and M. PPorter a n d W. W. M. orter
Abstract (CaS04.2Hz0) or lime (CaC03) (CaC03) was studied Amelioration of subsoil acidity using gypsum (CaS04.2H20) on sandy textured soils with low water holding capacity in a low rainfall environment. Field trials were established in 1989 1989 at two sites on yellow sandplain soils to investigate whether different rates, sources and combinations of gypsum and lime application could be used to increase wheat and lupin yields. Gypsum increased wheat yields by up to 45% in the first two 15% in the second season. growing seasons whereas lime increased wheat yields by up to only 15% The highest yields were generally recorded when gypsum and lime were applied together. The response of wheat to the various treatments varied both regionally and temporally and it is suggested that the inherent soil solution composition affected the magnitude and rapidity of wheat responses to gypsum. The rate of gypsum application affected the longevity of the wheat responses, with a low application rate (1 -1) increasing yields for only one (1 t ha ha-') season. No differences in wheat yields were recorded between different sources of gypsum or application rates higher than 3 t haha-'.1 . In contrast to wheat, wheat, lupin yields were substantially lower on gypsum-treated plots. The yield decline did not appear to be related to any simple nutritional factor and the gypsum effect was generally minimized when lime was added with the gypsum. The results indicated that lower rates of gypsum than used in previous subsoil amelioration studies studies were suitable for increasing wheat yields on sandy soils in low rainfall environments, and that gypsum should not be used if lupins are to be grown within at least 2 years of its application to the soil surface.
Introduction Introduction Subsurface acidity has been reported to impair plant growth and decrease decrease crop yields in many areas of the world. The main cause of the decrease in yields is stunted root growth due to high aluminium concentrations concentrations in the subsurface soil, soil, and therefore an inability of the plant to access access subsurface sources sources of water and nutrients when the surface surface soil dries out (Adams (Adams and Moore 1983; 1983; Sumner e t at. al. 1986). 1986). In some soils soils with subsurface acidity, it has been suggested that a et e r sse, e , is the A1 toxicity pper low calcium concentration in the subsoil, rather than Al al. 1988; 1988; Shainberg acidic subsoils (Bruce et at. main factor limiting plant growth in acidic e t at. al. 1989). 1989). et In the past, research from from field trials has often shown that the additiqn addition of lime is only effective at ameliorating subsurface subsurface acidity if it is fully fully incorporated into the layer of soil which is responsible for the decreased decreased yield (Reeve (Reeve and
1972; McKenzie McKenzie and Nyborg 1984; 1984; Pinkerton and Simpson 1986; 1986; Farina Sumner 1972; 1988). In contrast, a single application of a high rate rate of gypsum to and Channon 1988). the soil surface surface has been reported to substantially increase increase the yield of a range 200% within the first season season after application and maintain of crops by up to 200% al. several years (Hammel et at. higher yields than those in unamended plots for several 1985; Farina and Channon 1988; 1988; Sumner and Carter 1988; 1988; Shainberg et at. al. 1989; 1989; 1985; al. 1991). 1991). The use of gypsum for ameliorating subsurface acidity has McCray et at. recently been comprehensively comprehensively reviewed by Shainberg et at. al. (1989). (1989). Although increases with gypsum are often lower than when lime is fully fully incorporated yield increases profile, it has been suggested suggested that the improvement in plant throughout the soil profile, farming growth when gypsum is surface-applied is more economically viable in farming systems (Farina and Channon 1988). 1988). considerable research effort in recent years, the actual mechanisms Despite considerable by which gypsum ameliorates subsurface acidity are still poorly understood. In responses to only a single single gypsum addition, most studies have investigated crop responses single, high rate of source (usually mineral gypsum or phosphogypsum) phosphogypsum) and a single, Responses of wheat to gypsum application have only been gypsum application. Responses al. 1989) 1989) and lupin responses appear to have not reported once (Shainberg et at. been reported at all. all. The regional variability of the crop responses also does not difficult to predict, therefore, the appropriate appear to have been studied. It is difficult rate or source source of gypsum to best ameliorate subsurface acidity for different different soil crops, other than those reported, and it is not possible to types, climates or crops, predict the longevity of crop responses to t o different rates of gypsum application. application. 1. Selected soil properties of the yellow sandplain soil at Carrabin Table 1. Soil Soil type: type: Parent material: Classification: Classification:
Deep yellow sandplain soil Deeply weathered laterite and aeolian sands Gn 2·21 2.21 (Northeote (Northcote 1979); 1979); Aquic Hapludox (USDA) (USDA) Description
Topsoil (0-10 (0-10 cm) Topsoil A loamA sandy loam
(15-25 cm) Subsoil (15-25 B loamB sandy clay loam
Water holding capacity (% vol) vol) Organic matter (%) Dominant clay mineral Structure I M KCI KC1 exchangeable Al A1 1M (mg (mg kg-l) kg-1) CEC (cmol (cmolc kg-')l ) c kgAEC (cmol (cmol,a kgkg-')l ) pzc PZC
5.5 5·5 1.3 1·3 kaolinite kaolinite massive 29.7 29·7
10.7 10·7 0.7 0·7 kaolinite massive 86.7 86·7
1·56 1·20 4·80
4·63 0·20 4·05
A A B
81.6% 81.6% sand, sand, 8·1% 8.1% silt, silt, 10·3% 10.3% clay. 72.2% 72.2% sand, sand, 8·0% 8.0% silt, silt, 19·8% 19.8% clay. clay.
Subsoil acidity decreases decreases crop yields in several several areas of Australia, Australia, including a Subsoil lo66 hay ha) of naturally acidic acidic yellow sandplain soils in the eastern (c. 10 large area (c. field research has demonstrated that wheatbelt in Western Australia. Recent field p ~ in) the soil solution below a high concentration of total aluminium (>20 pM) 15 em cm depth decreases decreases wheat yields on these soils (Carr et at. 15 al. 1991). 1991). The
sandy texture and low water-holding capacity of yellow sandplain soils (Table 1) 1) (300-350 mm per annum) annum) are and the low rainfall of the eastern wheatbelt (300-350 considerably different to the heavier textured soils and higher rainfall environments (750-2000 mm) in other regions of the world in which plants have previously (750-2000 been reported to respond positively to gypsum. Evaporation exceeds rainfall in every month, giving an annual average water deficit of approximately 2300 mm. sufficient gypsum or lime could leach into It is uncertain, therefore, whether sufficient the subsoil despite the coarse texture of the soil. soil. In Western Australia, Australia, high purity grades of mineral gypsum occur naturally around many salt lakes and are potentially a readily available and relatively cheap source of gypsum for farmers farmers to use. The aims of this paper are to establish the response of wheat and lupins to different rates and sources of surface-applied gypsum and to compare responses to gypsum with responses obtained by applying lime to the surface of a sandy soil in a low rainfall al. 1994), the changes rainfa11 region. In a companion paper (McLay et at. to soil solution chemical properties following following the application of gypsum and lime to the soil surface and the possible mechanisms of amelioration are discussed. discussed. Table 2.
(mm) at Merredin (55 (55 km from Annual rainfall (mm) Carrabin) and Trayning Trayning
1989 1989 1990 1990 1991 1991 av. Long term avo (1903-1993) (1903-1993)
285 355 350 316
320 344 302 N.A. A
N.A., not available.
Materials and Methods Selection Site Selection Two field field sites were established in the eastern wheatbelt of Western Australia at Carrabin 0 0 0 0 (32 S., 117 E.) and Trayning (31 S., 118 E.). The sites were selected on the basis of low (32'S., 117OE.) (31°S., 118OE.). I-tM)~ in) the subsoil solution at pH «pH (20 p 15-25 15-25 em. cm. The sites had a similar soil type and annual rainfall (c. 300-350 300-350 mm); mm); characteristics 1. Annual rainfall for the period 1989-91 at the of the soil at Carrabin are given in Table 1. two sites is given in Table 2. Rainfall was obtained from the farmer at Trayning, and a meteorological station at Merredin which is 55 km west of Carrabin. The main difference between the soil at the two sites was a higher ionic strength and concentration of cations and anions in the soil solution at a t Trayning than the soil from Carrabin due to the closer proximity of the site to salt lakes. The maximum ionic strength in the soil solution in unamended subsoil at (c. 0·002 0.002 M). A soil test recently a t Trayning (c. (c. 0·006 0.006 M) was higher than at Carrabin (c. published for the prediction of Al 1991) predicts A1 toxicity in yellow sandplain soils (Carr et al. 1991) that Al A1 would be less toxic to wheat in the soil solution at Trayning than the soil at Carrabin due to its higher ionic strength, and it was considered, therefore, that the wheat grown at Trayning may be less responsive to gyspum or lime application than the wheat grown at Carrabin.
Field Trial Establishment Management of the trials was in accordance with the local district practice-that is, is, a practice-that rotation of 2 years of wheat followed followed by 11 year of lupins. The trials consisted of an incomplete
following gypsum and lime treatments which were replicated factorial design comparing the following four times: 'lakeside' !R'psumj ffypsum; phosphogypsum); phosphogypsum)j three sources of gypsum (fine and coarse 'lakeside' (1, 3 and 9 t haha- ) for each sourcej source; three rates of gypsum application (1, ha-');1 )j two rates of lime (2 and 4 t ha1 1 limexgypsum (1 t haha-'fine gypsum+:! t haha-'lime; ha-' 1 fine gypfour lime x gypsum treatments (1 fine gypsum+2 limej 3 t ha1 limej 1 t ha- 1 finegypsum+4 t ha- 1 limej 3 t ha- 1 finegypsum+4 t ha- 1 sum+2 t ha1 ha-'finegypsum+4 ha-'lime; ha-'finegypsum+4 ha-' ha-'lime; lime) ; lime)j • control (no lime or gypsum added).
• • • •
Chemical analysis of the three gypsum sources used to ameliorate subsurface acidity
Cd 1 (mg (mg kgkg-') )
F F 1 (mg (mg kgkg-') )
Phosphogypsum Fine lakeside Coarse lakeside