Abstract
A field experiment investigating amendments of organic material including farmyard manure, paper factory sludge and crop residues combined with fly ash, lime and chemical fertilizer in a rice-peanut cropping system was conducted during 1997–98 and 1998–99 at the Indian Institute of Technology, Kharagpur, India. The soil was an acid lateritic (Halustaf) sandy loam. For rice, an N:P:K level of 90:26.2:33.3 kg ha−1 was supplied through the organic materials and chemical fertilizer to all the treatments except control and fly ash alone. The required quantities of organic materials were added to supply 30 kg N ha−1 and the balance amount of N, P and K was supplied through chemical fertilizer. Amendment materials as per fertilization treatments were incorporated to individual plots 15 days before planting of rice during the rainy season. The residual effects were studied on the following peanut crop with application of N:P:K at 30:26.2:33.3 kg ha−1 through chemical fertilizer alone in all treatments, apart from the control. An application of fly ash at 10 t ha−1 in combination with chemical fertilizer and organic materials increased the grain yield of rice by 11% compared to chemical fertilizer alone. The residual effect of both lime and fly ash applications combined with direct application of chemical fertilizer increased peanut yields by 30% and 24%, respectively, compared to chemical fertilizer alone. Treatments with fly ash or lime increased P and K uptake in both the crops and oil content in peanut kernel compared to those without the amendments. Alkaline coal fly ash proved to be a better amendment than lime for improving productivity of an acid lateritic soil and enriching the soil with P and K.
Introduction
Sustainable development in agriculture and the potential yield of crops can be achieved through scientific management of land and crop. For attaining the potential yield of crops, supply of nutrients at the desired level and at the appropriate time is indispensable. In intensive cropping, chemical fertilizers largely meet this requirement due to their easy availability and rapid nutrient supplying capacity. However, indiscriminate and continuous use of such chemical fertilizers for years may lead to yield instability and also pose a threat to soil health, particularly with respect to micronutrient deficiency and fertilizer-related environmental pollution (Prasad & Power, Citation1995). The problem is more critical in acid lateritic soils, where nutrient imbalance exists due to deficiency bases and toxicity of Fe, Al or Mn. The physico-chemical properties of acid soils are largely governed by their organic matter content (Moody et al., Citation1997). However, acid lateritic soils are characteristically low in the content of this important soil fraction. Periodic liming is thought to expand the natural resources present in such soils by raising pH to a favourable range (Tisdale et al., Citation1985). Therefore, addition of organic matter and liming are important for restoring and improving the productivity of acid lateritic soils.
Organic fertilization is mostly achieved through the application of bulky farmyard manure (FYM). However, its limited availability and high cost necessitates utilization of other potential sources. Paper factory sludge (PFS), a by-product of the paper industry, consists of mainly cellulose fibre and is a good source of organic matter. Crop residues (CR) are also important sources of organic fertilizer as they are readily available, and in quick succession, particularly under intensive cropping. Lime is a costly input. Alkaline fly ash (FA), a coal combustion waste of thermal power plants, is considered to be a potential acid neutralizing source (Adriano et al., 1980; McCarty et al., 1994). Coal is fossilized vegetation and its ash is expected to be rich in minerals essential for plant growth and may further prove its suitability in agricultural application. Rice is an indispensable crop in high rainfall regions. The economic part of the peanut crop is grown underground and hence changes in soil physico-chemical properties are likely to have influence on crop yield and quality. Bearing this in mind, the present investigation was formulated to study the effects of different fertilization sources involving organic and chemical fertilizers, and soil amendment on yield and nutrient uptake of crops under a rice-peanut cropping sequence, dehydrogenase activity and changes in properties of acid lateritic soil.
Methods
Test soil and materials
The experiment with the rice-peanut cropping system was conducted at the Research Farm of the Agricultural and Food Engineering Department, Indian Institute of Technology, Kharagpur (22°19′ N, 87°19′E), India during the years 1997–98 and 1998–99. The climate of this region is warm and humid; annual mean precipitation ranges from 1300 to 1500 mm. The soil is acid lateritic (Haplustalf) and sandy loam in texture. The physical and chemical properties of the initial soil sample collected from 0–20 cm depth are presented in . In this investigation, rice (Oriza sativa L.) crop was grown during the rainy season (June–October) of 1997 (first season) and 1998 (third season) and peanut (Arachis hypogaea L.) during the dry season (January–May) of 1998 (second season) and 1999 (fourth season). Rice variety IR 36 and peanut variety AK 12–24 were used for the experiment.
Table I. Physical and chemical properties of soil (0–20 cm depth) of experimental site.
Treatment design
The effect of different fertilization sources including organic and chemical fertilizer with or without soil amendments was studied on rice and the residual effect of the same treatments with direct application of chemical fertilizer (CF) was assessed for subsequent peanut crop grown in sequence. For the rice crop, FA as a soil amendment was applied at 10 t ha−1 along with CF and organic material such as FYM or PFS or peanut haulm as CR. The other soil amendment, lime (L) was applied at 2 t ha−1 in combination with CF and FYM or PFS for comparison with FA. The quantity of organic material, i.e., FYM, PFS and CR was chosen to supply 30 kg N ha−1. A uniform nutrient level of 90 kg N, 26.2 kg P and 33.3 kg K ha−1 was maintained through organic materials and CF. There were two further treatments, where nothing was added (absolute control) and a second where only FA at 10 t ha−1 was applied. They were included for comparative assessment of treatment effects. The experiment comprising 12 treatment combinations was laid out in a randomized complete block design with three replications. The plot size was 6×4 m. The soil amendment materials (FA, L) and organic materials (FYM, PFS, CR) as per treatment were incorporated in the plots at 15 days before transplantation of rice. The sources of CF used for N, P and K were urea, single superphosphate and muriate of potash, respectively. Of the total CF, one-third N, full P and K were applied as basal dressing at the time of transplanting and the remaining amount of N was applied as a top-dressing in two equal portions at 25 days after transplanting (DAT) and 45 DAT. Rice seedlings 25 days old were transplanted at two to three seedlings per ridge with row spacing of 20 cm and plant spacing of 15 cm.
The peanut crop was grown after harvest of the rice in the same layout. The recommended nutrient level of 30:26.2: 33.3 kg ha−1 of N:P:K was supplied through chemical fertilizer uniformly in all the treatments except the control at the time of sowing. Row spacing of 20 cm and plant spacing of 15 cm were maintained. The experiment was repeated in the second year with repeated treatments for better appraisal of the treatment effects.
The physical and chemical properties of the materials used in the experiment are given in .
Table II. Physical and chemical properties of the soil amendments used in the experiment.
Yield attributes and yield
An area of 1 m2 was harvested in the centre of each plot for determination of yield of both rice and peanut. Panicles per m2 in rice and shelling percentage in peanut were also recorded from the same area. For rice, 10 ridges and for peanut 10 plants were selected randomly avoiding border rows and the centre 1 m2 area at harvest. Grains per panicle in rice and pods per plant and 100-kernel weights in peanut were determined from these samples. Grain and straw yield of rice were recorded at 12 and 14% moisture content, respectively. Pod and haulm yield of peanut were recorded at 10% moisture content.
Plant and soil chemical analysis
Representative plant samples were collected at harvest, cleaned with distilled water and dried in a drying chamber at 70°C until constant weight was achieved. The N and P contents of plant materials were estimated by the modified Kjeldahl, and molybdenum blue methods, respectively (Chapman & Pratt, Citation1961) while the K contents were estimated after wet acid digestion using triacid mixture (Jackson, Citation1973). Oil contents in peanut kernel were estimated by the solvent extraction method (AOAC, Citation1950).
Soil samples after harvest of each crop viz. first season (S1), second season (S2), third season (S3), and fourth season (S4) were collected with the help of a screw augur from 0–20 cm depth in each plot from five randomly selected spots and a composite sample was made for chemical analysis (organic carbon, pH, and available N, P, and K content). Before harvest of the peanut crop, soil samples were collected with the help of a core sampler to determine bulk density. Potential dehydrogenase activity in soil was assayed using the 2,3,5-triphenyl tetrazolium chloride reduction method (Casida, Citation1977). Soils were mixed with CaCO3 at a ratio of 0.1 g per 8 g soil to maintain pH around 6.8. After CaCO3 addition, soil was dispensed inside tubes and a 0.5 ml double-strength glucose solution was added. This was immediately followed by addition of 0.5 ml water and rubber stoppers were inserted. Samples were incubated for 24 h at 37°C. After incubation, the concentration of water insoluble red-coloured 2,3,5-triphenyl formazon was recorded colorimetrically for qualitative assessment.
Statistical analysis
The recorded data were subjected to statistical analysis by the standard analysis of variance technique (Gomez & Gomez, Citation1984). The treatment differences were tested at 5% level of significance, following the F-test. Different parameters were correlated and the regression co-efficient was calculated using a standard procedure (Snedecor & Cochran, Citation1967).
Results
Rice yield components and yield
All fertilization treatments with CF promoted yield components such as panicles per m2 and grains per panicle compared to the control, and the FA was equivalent to the control (). During the first season, all additional combination + CF treatments were comparable to CF for yield components. A similar trend was also noted while comparing these fertilization treatments for grains per panicle during the third season, whereas for panicles per m2 the treatments FA + CF, FA + FYM + CF, FA + PFS + CF and FA + CR + CF were better than CF.
Table III. Yield components and yield of rice as influenced by direct application of different fertilization treatments during rainy seasons of 1997 (first season) and 1998 (third season).
The data shown in reveal higher yields (grain and straw) under all the fertilization treatments compared to the control and the FA. The FA or lime-based fertilization treatments containing organic materials and CF had no yield advantage over treatment with CF during the first season. However, in the third season, the FA-based fertilization treatments (FA + CF, FA + FYM + CF, FA + PFS + CF and FA + CR + CF) were better than the CF. The lime-based fertilization treatments were comparable to the treatment CF for grain and straw yield.
Nutrient uptake by the rice crop
From the data in , it is apparent that in the first season, the treatment FA was equivalent to the control for N and K uptake in grain or straw. For uptake of P, the treatment FA was better than the control. The FA-based treatments containing organic fertilizer and CF were equivalent to CF for N uptake in grain or straw. However, for P and K uptake, the FA-based treatments were better than CF or the treatments of similar combinations but without FA. The FA-based fertilization treatments were superior to lime-based treatments in the uptake of all these nutrients in grain or straw. In the third season, the FA-based fertilization treatments containing organic materials and CF promoted uptake of all the nutrients in grain or straw compared to the fertilization sources of similar combination but without FA, and the CF. The FA-based fertilization treatments were better than lime-based treatments in uptake of P and K.
Table IV. Uptake (kg ha−1) of nitrogen (N), phosphorus (P) and potassium (K) in rice grain and straw as influenced by direct application of different fertilization treatments during rainy seasons of 1997 (first season) and 1998 (third season).
Peanut yield components and yield
The residual effect of different fertilization treatments was significant in increasing the number of pods per plant and 100-kernel weight compared to the control (). The effect of FA and lime-based fertilization treatments was comparable for 100-kernel weight and shelling percentage. These treatments were better than the CF in increasing the number of pods per plant.
Table V. Effect of different fertilization treatments on yield components and yield of peanut during dry seasons of 1998 (second season) and 1999 (fourth season).
The effect of different fertilization treatments resulted in higher pod and haulm yield compared to control (). The FA or lime-based fertilization treatments FA + FYM + CF, FA + PFS + CF, L + FYM + CF and L + PFS + CF were better than the CF with regard to pod yield. The increase in pod yield under FA-based treatments was 24% compared to the CF, while it was 30% under lime-based treatment (average of two seasons). However, for haulm yield, the effect of these fertilization treatments was equivalent to CF.
Nutrient content of peanut crop
Under the residual fertilization treatments, the uptake of N, P and K in kernel and haulm was higher compared to control in both the second and fourth seasons (). In the second season, FA or lime-based fertilization treatments resulted in higher uptake of N, P and K in kernel compared to treatments without FA or lime. For uptake of these nutrients in haulm, all the fertilization treatments were equivalent to the CF. The amendment FA in combination with organic material and CF was equivalent to lime in similar combinations for uptake of N, P and K in the kernel. In the fourth season, residual effects of different fertilization treatments were better than the CF for uptake of all the nutrients in kernel. The FA or lime-based fertilization treatments caused significant increase in uptake of P and K in kernel compared to the treatments of similar combination but without FA or lime. Higher uptake of all these nutrients in haulm was recorded under FA or lime-based fertilization treatments compared with the CF.
Table VI. Effect of different fertilization treatments on uptake (kg ha−1) of nitrogen (N), phosphorus (P) and potassium (K) in peanut kernel and haulm during dry seasons of 1998 (second season) and 1999 (fourth season).
Peanut oil content
All the fertilization treatments increased the oil content of peanut kernel compared to the control, in both the seasons (). Among the different fertilization treatments, the lowest content was recorded under the CF. The residual effect of treatments with FA or lime resulted in higher oil content than those without it. Between FA and lime-based fertilization treatments, variation in oil content was negligible.
Figure 1. Effect of different fertilization treatments on oil content of peanut kernel during dry season of 1998 (second season) and 1999 (fourth season). The bars represent SE.
Residual soil properties
At harvest of peanut crop, bulk density of soil was lower under all the fertilization treatments compared to control (). The FA and lime-based fertilization treatments including organic materials and CF resulted in lower bulk density of soil compared to the CF. For FA and lime-based treatments, it was lower under the former than the latter.
Figure 2. Effect of different fertilization treatments on bulk density, organic carbon content, pH, and available nitrogen (N), phosphorus (P) and potassium (K) content of soil after harvest of rainy and dry season crops during 1997–1999.
After each season, crop, organic carbon content and pH of soil were higher under all the fertilization treatments compared to control (). Continuous application of only CF resulted in lower organic carbon and pH compared to the integrated use of CF, organic fertilizer and soil amendment (FA or lime). Use of FA in combination with organic fertilizers and CF resulted in higher organic carbon content and pH of soil compared to the treatments of similar combination but without FA. The FA-based fertilization treatments registered higher organic carbon and lower increase in pH of the acid soil compared to lime-based treatments.
Higher available N, P and K status of the soil was registered under all the fertilization treatments compared to control, after each season crop (). The FA-based fertilization treatments containing organic fertilizer and CF increased the available N, P and K status of soil compared to those without FA and the treatment CF after each season crop. The FA-based fertilization treatment recorded higher available P and K status of soil compared to the lime-based ones after each season crop. This variation was marginal for available N.
The dehydrogenase activity of the soil () was higher in the peanut field compared to the rice field. The FA and lime-based treatments had higher dehydrogenase activity compared to those without FA and lime, and the CF.
Figure 3. Effect of different fertilization treatments on dehydrogenase activity of soil after harvest of rice during rainy seasons 1997 and 1998 and after harvest of peanut during dry seasons 1998 and 1999. The bars represent SE.
Discussion
The increase in rice yield is associated with increase in the panicle number and the grains per panicle (data not shown). Analysis on uptake of nutrients revealed an enhanced uptake of nutrients under the treatments involving fly ash in combination with organic material and chemical fertilizer. Singh and Singh (Citation1986) reported an increase in the uptake of N, P and K by rice with application of fly ash as high as 20% by weight of the soil. It is thus apparent that any increase in uptake of the essential plant nutrients by the application of fly ash and organic material increased the yield components and thereby the grain yield of the crop. Study on heavy metal uptake by mustard and peanut crops due to repeated use of fly ash-based integrated fertilizer shows a marginal increase of Cd, Ni, As and Se (Mittra et al., Citation2000; Rautaray et al., Citation2002). However, the content of these heavy metals was within safe limits.
Increased uptake of nutrients in the crop is associated with their increased soil availability under integrated fertilization treatments including FA, organic materials and CF. The chemical composition of the materials used in the experiment () indicates that application of FA at 10 t ha−1 supplied very low amounts of organic carbon (27 kg), but considerable amounts of phosphorus (32 kg) and potassium (25 kg). However, the organic materials such as FYM, PFS and CR, each applied at 30 kg N ha−1, supplied a substantial quantity of organic carbon (500 to 1000 kg) besides supplementing nutrients. Thus, blending of FA with organic materials in suitable proportions formed a complete mixture of organic carbon and nutrients essential for boosting the crop yield, especially for an acid lateritic soil. Furthermore, FA accelerated the mineralization of organic matter in acid lateritic soil (Sing et al., Citation1994; Khan & Khan, Citation1996) besides being a source of most of the essential plant nutrients. Thus, its application promoted the nutrient supplying capacity of the soil and benefited the crop through enhanced uptake and thereby the yield.
The physico-chemical properties of soil influence the availability of nutrients in the soil and thereby their content in the crop. A decrease in bulk density facilitates the roots to proliferate and consequently the potential for plants to extract water and nutrients (Allison, Citation1973), and thereby the yield. This is evident from significant and negative correlation between bulk density of soil and uptake of nutrients by peanut crop (data not shown). Also, lower bulk density may facilitate easy penetration of gynophore (future pod) and subsequent bulking of it. The fly ash-based fertilization treatments with organic material and chemical fertilizer resulted in lower bulk density of soil compared to the continuous use of chemical fertilizer alone (). This might be due to lower bulk density of fly ash (0.93 Mg m−3) and organic material (0.48–0.61 Mg m−3) compared to soil (1.67 Mg m−3). Increase in soil pH by the application of lime reduced the fixation of available P and this increased its availability along with K (Mittra & Subbaiah, Citation1996). This change in nutrio-environment might be especially beneficial for the pods of the groundnut crop that can directly absorb the nutrients from the soil in the vicinity. In this experiment, this is apparent from the increased uptake of these nutrients by peanut pods and consequently the yield under the residual effect of fly ash or lime-based integrated fertilization treatments compared to the use of chemical fertilizer alone. The pH mediated crop response could be ascertained from the treatment where chemical fertilizer alone was applied and no change in pH was observed compared to initial soil value. As a result, the peanut crop failed to respond to added nutrients as much as observed under integrated fertilization including fly ash or lime. The findings are in agreement with those reported by Bekkar et al. (Citation1994), Jiahua et al. (Citation1995) and Sadhu et al. (Citation1997).
Besides physico-chemical properties, the biological properties of the acid lateritic soil in terms of dehydrogenase activity were also influenced favourably with the application of fly ash or lime along with organic material and chemical fertilizer. Soil microorganisms can act as agents of nutrient transformation and store carbon and nutrients in their own living biomass, acting as labile reservoirs for available nutrients with fast turnover (Brookes et al., Citation1985). The amount and activity of microorganisms therefore influences soil productivity and nutrient cycling. Higher organic carbon content and pH of the soil under fly ash or lime-based integrated fertilization treatments compared to only chemical fertilizers, perhaps accelerated the dehydrogenase activity of the soil (), which in turn increased the available nutrient status of the soil and consequently the crop yield. Dehydrogenase activity of soil was higher in the peanut crop field compared to the rice crop field. This is due to death of microbes under anaerobic condition of the rice field.
Differential response of rice and peanut to fly ash or lime application can be ascribed to the distinctive changes in soil physico-chemical properties due to varying field moisture conditions and also differential response of the crops to the available nutrients. Rice is grown under anaerobic (flooded) field conditions, which raises the pH of acid lateritic soil to near neutral level (Ponnamperuma et al., Citation1966). Therefore, the beneficial effect due to an increase in soil pH through application of fly ash or lime is expected to be of less influence on flooded rice compared to a crop such as peanut grown in aerobic (upland) conditions. As mentioned earlier, the application of fly ash or lime helps to increase the soil pH and thereby the availability of nutrients. Peanut being responsive to P and Ca (Panda, Citation1998; Singh et al., Citation1994) and their enrichment in soil by application of fly ash or lime may increase their availability. This is apparent from higher uptake of P by the crop under the treatments with fly ash or lime compared to those without it. Higher uptake of P and Ca under the fly ash-based treatments is reported (Rautray et al., 2003). Hence, application of fly ash or lime proved to be of greater advantage for peanut compared to rice.
The use of fly ash or lime had a favourable effect on the oil content of peanut kernel. Oil content is influenced by the composition of various essential elements in peanut kernel. With the use of fly ash or lime, the uptake of P by peanut kernel was increased and hence the oil content. Similar results are also reported by Rao and Singh (Citation1985).
Conclusions
Alkaline coal fly ash amendments are recommended for improving productivity of acid-lateritic soil and enriching the soil with P and K.
Acknowledgements
The research project was financed by Technology Information Forecasting and Assessment Council – Department of Science and Technology, New Delhi, India in collaboration with Kolaghat Thermal Power Station, West Bengal, India. B. N. Mittra, Principal Investigator of the project is gratefully acknowledged.
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