Research Article
Use of Gypsum to Increase Fertilizer Efficiency on Normal Soils
Not Available
Izhar-ul-Haq
Not Available
M. Salim
Not Available
Manzoor Ahmad
Not Available
Cultivation of high yielding crops, use of high analysis sulphur (S) free fertilizers and decreased use of organic and crop residues have resulted in a wide spread sulphur deficiency and low crop yields. Therefore sulphur application along with NPK has been found important in increasing crop yields of various crops (Saleem and Rahmatullah, 1986). Plants require sulphur in amounts slightly less than P (Dillon and Dev, 1980). The nutritive value of cereals is determined by the proportion of S containing amino acids, this S not only increase yield but also improve crop quality (Biswas and Tewatia, 1992). It has also been reported that S and N have broadly similar functions in the plants. Sulphur occurs in protein, especially in the amino acids, cysteine and methionine. Adequate S supply is essential to obtain maximum crop responses to N application in terms of yield (Schung, 1988) and grain quality (Schung et al., 1993). Bapat (1989) observed 32.4% increases in wheat yield with 20 kg S ha-1 ammonium sulphate as a source of sulphur. Singh and Saha (1995) revealed that the magnitude of grain yield response in maize to 20 kg S ha-1 was 730 kg ha-1. Dangarwala et al. (1995) and Subbaiah et al. (1992) in separate experiments determined that application of 30 kg S ha-1 had significant residual effect on the subsequent maize-groundnut and groundnut wheat cropping systems. The economic benefits derived were higher in maize-groundnut system with a benefit-cost ratio of Rs. 30:1 as compared to benefits obtained from groundnut-wheat system as Rs. 8:1. Studies on sulphur nutrition of plants have not received enough attention in Pakistan. Hence very little is known about the sulphur status of its soils and sulphur requirements of its crops (Saleem and David, 1987; Saleem and Rahmatullah, 1986). Gypsum being abundant and a cheaper source of sulphur. It has been used for the reclamation of saline sodic soils at various places in the country for reclamation of sodic soils and under brackish waters (Hussain et al., 2000 ). The normal soil has showed favorable response compared to salt affected soils (Ahmad et al., 2001). Therefore, it was contemplated to study its effects on the efficiency of NPK fertilizers under normal soil conditions.
The studies were conducted on normal soil and water conditions to observe the effect of gypsum on fertilizer use efficiency during Kharif 1996 and Rabi 1996-97 at two locations i.e. ARI, Tarnab and Qalla, district Charsada. The design of the experiment was randomized complete block with six treatments and three replications. The treatments were as follows:
T1 | NPK (120, 90, 60 kg ha-1) with 0 kg ha-1 gypsum. |
T2 | NPK (60, 45, 30 kg ha-1) with 0 kg ha-1 gypsum. |
T3 | NPK (120, 90, 60 kg ha-1) with 500 kg ha-1 gypsum. |
T4 | NPK (120, 90, 60 kg ha-1) with 1000 kg ha-1 gypsum. |
T5 | NPK (60, 45, 30 kg ha-1) with 500 kg ha-1 gypsum. |
T6 | NPK (60, 45, 30 kg ha-1) with 1000 kg ha-1 gypsum. |
Plot size at both the sites was 6 x 6.7 m2 with row to row distance 30 cm for wheat and 75 cm for maize. Wheat variety inqalab 91 and maize variety kissan were sown. All fertilizers at both times and locations were applied at planting except N which was applied in two splits i.e. half at sowing time and the rest half at early growth stage.
Plant samples were taken from rows at the 50% silking stage for analysis. The leaves below the silk were taken for this purpose. Fifty to hundred leaves were from top four leaves of the wheat plants before tasseling. The leaf samples dried at 70oC to constant weight were ground by a Wiley Mills.
Soil samples collected before sowing and after harvest of the crop were analyzed for pH, ECe and other physico-chemical characteristics (Richards, 1954). The data collected were subjected to statistical analysis according to Gomez and Gomez (1976).
A significant (P < 0.01) effect of gypsum application was observed on the efficiency of fertilizers used during the study at Qalla site. Effect of gypsum application on grain (3605 kg ha-1) and stalk (9922 kg ha-1) yield of maize showed that gypsum was effective enough to increase the efficiency of added full dose of fertilizers with 1000 kg ha-1 gypsum (Table 1). Addition of gypsum enhances the production of biomass and seeds in the saline sodic soils (Ramzan, 2001). However, in the present studies the normal soils also favored the plant growth compared to salt affected soil. The reason could be that the addition of gypsum had increased the availability of macro-nutrients and thus brought significant increase in straw and grain yield (Singh and Saha, 1995). Maximum grain (3605 kg ha-1) and stalk (9922 kg ha-1) yield were given by 100% recommended fertilizers and 1000 kg ha-1 gypsum application while minimum grain (2248 kg ha-1) and stalk (7935 kg ha-1) yield was given by 50% of the recommended fertilizer dose without the combination of gypsum (Table 1).
Application of gypsum on grain and stalk yield of maize at Tarnab was not effective enough to increase the efficiency of added fertilizers in the first year. It was because the experiment conducted at a field had already sufficient amount of major plant nutrients. So the addition of gypsum could not bring significant increase in the grain and straw (non-significant) yield (Table 2). However, maize grain yield decreased significantly (P < 0.05) for the year 1997 (Table 3).
Table 1: | Effect of gypsum application on maize yield at Qalla under normal soil conditions in 1996 |
Treatment means for grain and stalk yield are significantly different among them (P < 0.01). |
Table 2: | Effect of gypsum application on maize yield at Tarnab under normal soil conditions in 1996 |
Treatment means for grain and stalk yield are not significantly different among them (P < 0.01 and 0.05). |
Table 3: | Effect of gypsum application on maize yield at Tarnab under normal soil conditions in 1997 |
Treatment means for stalk yield are not significantly different among them (P < 0.01). |
Table 4: | Effect of gypsum application on wheat yield at Qalla under normal soil conditions in 1996 -1997 |
Treatment means for grain yield is significantly different (P <0.01) while straw yield is significantly different at (P < 0.05). |
Table 5: | Effect of gypsum application on wheat yield at Tarnab under normal soil conditions in 1996-97 |
Treatment means for grain and stalk yield are not significantly different among them (P < 0.01 and 0.05). |
Table 6: | Plant nutrient status of experimental field at Qalla and Tarnab after wheat 1996-97 |
Treatment means are not significantly different (P < 0.01 and 0.05). |
Table 7: | Plant nutrient status of experimental field at Tarnab 1996-97 |
Treatment means are not significantly different at both (1 and 5%) levels of significance. |
The decreased effect of gypsum may be due to decreased availability of plant nutrients. Higher grain yield of maize during the first year of gypsum application might be due to enhanced available supply of Ca2+ and S in the soil. The low solubility of gypsum may be another reason (Richards, 1954). In the second year availability of gypsum enhanced and had a significant effect on the crop yield. Haq (2001) has observed a non-significant increase in the yield of maize (grain and stalk) during the reclamation of a saline sodic soil. In the present experiment an increase in the yield may be related to the addition of gypsum as a fertilizer.
There was a significant (P < 0.05) effect of various rates of gypsum application on the efficiency of fertilizers used under wheat cultivation at Qalla (Table 4). The response of the wheat crop to fertilizers at both the sites was similar to that of maize crop. The response at Tarnab was not significant in this case also (Table 5). The experimental site has effect on the productivity of crop which is mostly due to different resources available (fertilizers, nutrients) to the crop plant. The same has been observed in the present study. Therefore different results at different sites have been recorded.
Nutrient uptake: Effect of fertilizers and gypsum application on the uptake of P and K was not prominent. However, there were non significant differences observed on both sites. Uptake of P was suppressed in the presence of higher doses of gypsum and half dose of NPK at Qalla site, but it was unaffected at Tarnab (Table 6). Uptake of Zn by the plant was higher at Tarnab (69 mg kg-1) compared to Qalla (39 mg kg-1). Uptake of Cu was not affected by the treatment at both the sites. Uptake of Mn (138 mg kg-1) at Qalla site is higher than that of Tarnab (33 mg kg-1). But concentration of Fe at both the sites shows a reverse order. The concentration of both these ions increased during the second year., which reveals that gypsum has positively affected the release of micronutrients. There is a clear cut antagonistic effect shown by the Mn and Fe during 1997 at Tarnab in this study (Table 7).
Gypsum has effectively been used for the reclamation of salt affected (sodic ) soils. Its use on the normal soils has also been explored in the present studies. A significant increase in the dry matter and grain yield has been recorded and release of micronutrient specifically Mn and Fe is an added advantage of gypsum use in normal fields.