effect of rice based six multiple cropping sequences under two cycles of crop rotations on yield and...

Plant and Soil 127: 251-258, 1990. © 1990 Kluwer Academic Publishers. Printed in the Netherlands. PLSO 7661

Effect of rice based six multiple cropping sequences under two cycles of crop rotations on yield and fertility status of soil

B. PRASAD and S.M. UMAR Department of Soil Science, Rajendra Agricultural University, Bihar, Patna Campus, Patna 800 001, India

Received 20 January 1988. Revised May 1990

Key words: crop rotations, copper, fertilizers, iron, manganese, phosphorus, potassium, zinc

Abstract

A field experiment was carried out to study the effect of various crop rotations, of high yielding varieties of cereals, pulses, fodders, tubers and oilseeds, on the performance of the crops and the fertility status of the soil over two crop-rotation cycles. The yields of rice (Oryza saliva L.), potato (Solanum tuberosum L.) and onion (Allium cepa) crops were found to be decreasing. The yields of wheat (Triticum aestivum L.) and mustard (Brassica juncea coss), were not affected, while the yield of moong (Phaseolus aureus Roxb.) showed a tendency to increase. Rotations which included berseem (Trifolium alexandrinum) increased the organic carbon content of the soil and there was a slight lowering of the pH with the highest application of phosphatic fertilizer. The accumulation of available potassium was greater in the treatments where the highest amount of fertilizer was applied. The available nitrogen content of the soil increased with application of nitrogen and the balance sheet of nitrogen, phosphorus and potassium showed a positive trend. The continuous cropping of high yielding varieties showed a reduction in the available zinc and iron status of the soil, whereas available manganese and copper increased. The available micronutrients, except manganese, did not correlate significantly with soil pH.

Introduction

Investigation of the fertility status of soil under different multiple cropping sequences is of im- portance in present times. Crops grown in different cropping sequences remove varying quan- tities of nutrients from soil which affects its fertility status (Bolton et al., 1979; Dhillon and Dev, 1979; Dormaar et al., 1979). Cereal crops have been reported as depleting soil fertility to a relatively large extent, whereas legumes are con- sidered beneficial in this respect (Sen Gupta, 1965; Sharma et al., 1980). The various patterns of crop rotations, depending upon their intensity and the nature of the crops, exhaust the soil differently and may influence soil fertility status differently (Deka and Singh, 1984; Dhillon and

Dev, 1979; Jon and Robert, 1980). The present investigation was conducted with crops of high yielding varieties of cereals, pulses, fodders, tubers and oilseeds grown in a variety of crop sequences in different fixed crop rotations with recommended programs of practices. Since these crops remove considerable amounts of nutrients from soil, information is needed to understand the stress on soil nutrients in order to assess the nutrient balance over a period of time.

Materials and methods

Representative soil samples were collected from twenty four plots of the field experiment conducted at The Agricultural Research Institute,

252 Prasad and Umar

Table 1. Various crop rotations and the amount of N, P and K fertilizers applied in two cycles

S1. No. Treatment No. Crop rotations Fertilizer rate (kg ha 1)

N P K

1. T ~ Rice-wheat-fallow 2. T 2 Rice-wheat-moong 3. T~ Rice-gram-rice 4. T~ Rice-potato-onion 5. T,~ Rice-mustard- rnoong 6. T 6 Rice-berseem-fallow

360 160 80 400 240 80 360 200 120 560 340 430 320 160 120 200 160 140

Sheikhpura, Patna. The treatments consisted of six fixed crop rotations as shown in Table 1. The rates of application of fertilizers to the crops are given in Table 2 and the amount of fertilizers added during the whole period of experiment is in Table 1. Urea, single super phosphate and muriate of potash were the respective sources of N, P and K in all the treatments. The experiment was laid out in a randomized block design with six rotations as treatments, each of which was replicated four times. The plot size was 6 m x 4m. The soil samples were collected from treated plots after each crop. The samples were air dried, ground to pass through 2 mm sieve and used for the various analyses. The soil properties were clay 46.25%, silt 19.56%, sand 35.71%, pH 7.1 (soil:water ratio 1:2, Jackson, 1967), Organic carbon 0.57% (Walkley and Black, Jackson, 1967) available nitrogen 302.00 kg ha-~ (alkaline potassium permanganate method, Subbiah and Asija, 1956), available phosphorus 41.00kg ha -~ (Olsen method - extraction using 0.5 M NaHCO 3 (pH 8.5), Jackson, 1967), available potassium 375.00 kg ha -~ (extraction method in IN NH4OAC, Jackson, 1967). At the end of the experiment soil samples were collected (0-15 cm layer) from each treatment. These soil samples were processed and analysed for selected soil

constituents as mentioned above. Available Zn, Cu, Fe and Mn were determined by DTPA method (Lindsay and Norwell, 1978).

Results and discussion

Crop per fo rmance

The data presented in Table 3 show the yield of various crops obtained under two cycles of different crop rotations. In general the yield of rice was low in the third year of experimentation in all the treatments except T 6 (rice-berseem- fallow). In three years rotations of 200% intensity, where rice was grown, its yield showed a decreasing trend, but the difference was small, although in T 6 (rice-berseem-fallow), the yield was lower in the first year, but increased in second and third year due to cropping of legumes (berseem). The higher yield of rice in succeeding years in this t reatment may be due to the favourable effect of the berseem crop on soil fertility. The beneficial effects of legumes on succeeding crops has been reported by various workers (Ahlawat et al., 1981; Cooke, 1967; Deka et al., 1984). It is also evident from Table 3

Table 2. Rate of fertilizer application (kg ha -~) for different crops

Crops N P K

Wheat (Triticum aestivum L.) Variety: HP 1102 Gram (Cicer arietinum) Variety: RAU-52 Rice (Oryza sativa L.) Variety: Sita Moong (Phaseolus aureus Rox b.) Variety: T 4 Berseem (Trifolium alexandrinum) Variety: Meskaw-i Onion (Allium cepa) Variety: Patna red Mustard (Brassica juncea coss) Variety: Varuna Potato (Solanum tuberosum L.) Variety: Kufri Chandramukhi

100 40 20 20 40 20 80 40 20 20 40 0 20 40 50

100 50 75 60 0 40

100 80 120

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Effect of crop rotations on yield 253

that, in 300% cropping intensity of three years crop rotations, the yield of the rice crop was in decreasing order. Similar results that the yield of rice grain decreased progressively year after year have been reported (Sasidhar and Sadanandan, 1980). A slight increase was obtained in the second year in T~ (rice-potato-onion) but the increase was small. The decrease of rice yield was a result of the continuous cropping of cereal crops which depleted the fertility status of the soil to a greater extent, The yield of wheat showed a decreasing trend in treatment Tj (rice- wheat-fallow), but the yield level of the wheat crop remained more or less constant throughout the three years in T2 (rice-wheat-moong). The constant level of wheat yield could be due to the inclusion of legumes (moong) in this treatment. The higher yield of wheat has been reported by several workers due to the inclusion of a leguminous crop in a rotation (Joshi, 1972). The yield of rnoong in t r e a t m e n t s T 2 and T 5 was also of an increasing order throughout the experiment period. The yield of potato and onion showed a decreasing trend in T 4 (rice-potato- onion); both the crops were highly fertilizer re- sponsive and greatly depleted the soil of major and minor elements. The yield of mustard was not affected very much in a 300% cropping intensity over three years of cropping pattern.

Available nutrients

The data on the changes in various soil fertility parameters at the start of the experiment and after two cycles of fixed six-crop rotations arc presented in Table 4.

Organic carbon

in general the organic carbon content varies from the lowest 0.49, in T~ (rice-wheat-fallow), to the highest 0.70, percent in treatments T~ (rice-potato-onion) and T~, (rice-berseem-fallow). It is evident from Table 4 that after T~, (rice- berseem) and T 4 (rice-potato-onion), soil organic carbon was higher as compared to other treatments. This may be due to the fact that total biomass addition in T 6 w a s higher as compared to other treatments. Further, the biomass added by legumes is of a narrower C:N ratio as corn-

254 Prasad and Umar

Table 4. Various soil fertility parameters at the start and end of two cycles of crop rotations

Treatments pH Org. C. P205 K20 N (%) (kg ha -~) (kg ha-') (kg ha 1)

T 1 6.8 0.49 42.5 335 330 T 2 6.9 0.47 29.7 300 339 T 3 7.0 0.68 39.5 325 326 T4 6.9 0.70 46.7 350 330 T 5 6.8 0.68 31.7 332 341 T 6 6.7 0.70 37.7 325 345

SEM ( +- ) 0.09 0.09 6.17 30.47 2.48 At the start 7.1 0.57 41.0 375.0 302

of the expt.

pared to cereal which is expected to decompose more rapidly, thereby causing faster humification (Mysknow and Morrison, 1963). It was also reported that growing berseem in a rotation significantly increased the organic carbon content of soil (Acharya et al., 1953). It has also been reported that berseem was more efficient in the building up of soil organic matter than other legumes such as sweet clover and pea (Sharma and Singh, 1970). The increase in organic carbon content of the soil, from other treatments may be attributed to the accumulation of plant resi- dues (both roots and aerial parts), The increase in organic carbon in the soil by cultivating fertil- ized crops in a fixed rotation has been reported by earlier workers (Kanwar and Prihar, 1962).

Available phosphorus

The available phosphorus content of the soil is presented in Table 4. The data presented above in the table shows that it ranged from 29.7 kg ha -~ to 46.7 kg ha -1. The lowest value was in T 2 (rice-wheat-moong) and the highest in T 4 (rice- potato-onion). The data for available phosphorus indicated that there was a constant increase in the content of it in the soil due to fixed crop rotations and application of fertilizers except in treatments T 2, T s and T 6. The decrease was much lower in t reatment T 3. The increase in available phosphorus content in various treatments may be partly due to the application of phosphate fertilizers and partly due to the re- lease of fixed soil phosphorus in the course of time. The data also indicate that there was a slight lowering of the pH with the highest appli-

cation of phosphatic fertilizers which conforms with the findings of other workers (Singh et al., 1980). A decrease of available soil phosphorus with the passage of time may be partly due to the absorption of phosphorus by crops (data not reported in this paper) in the rotation and partly due to the fixation of added phosphorus in the course of time.

Available potassium

The available potassium status of soil is also presented in Table 4. The data presented in Table 4 indicate that it ranged from 300 kg ha-1 in T 2 (rice-wheat-moong) t reatment to the highest 350kg ha -1 in the T 4 (rice-potato-onion) treatment, showing a decreasing trend in all the treatments, from the initial value. The level of available potassium was higher in the treatment where the highest dose of chemical fertilizers were applied. The treatment T 4 showed the highest amount of available potassium in spite of high uptake of potassium (data not presented in this paper) by the crops. These results suggest that crop needs were partially met from the reserve potassium and that the potassium applied through fertilizers (Table 1) caused a build-up in the soil confirming earlier findings, but in con- trast to the findings which reported a decrease in soil potassium even with the application of fertilizer potassium for sixteen years (Findley, 1973). The high content of available potassium, prob- ably due to weathering of potassium minerals, contributed to an increase in the potassium status of the soil. This is in conformity with earlier findings (Prasad and Sinha, 1981). The

decrease in the available potassium status of the soil may be due to extensive cropping and deple- tion of soil potassium by the various crops. The application of potassium at higher levels of nitrogen and phosphorus, especially in high yielding varieties of crops and under intensive cropping systems, is necessary for the efficient utilization of other nutrients, particularly nitrogen. Con- tinued nitrogen applications at increasing rates, may eventually result in exhaustion of soil potassium.

A vailable nitrogen

The available initial status of nitrogen at the end of the experiment is presented in Table 4. The available nitrogen status of the soil varied from 330kg ha ~ (T~) to 345kg ha -~ ( T 6 ) . In general, available nitrogen content of soil accumulated with the application of nitrogen. Lower available nitrogen content was evident in the treatments having T~ (rice-wheat-fallow) treatment and T 4 (rice-potato-onion) treatment. This finding is in conformity with other findings that there is a lower available nitrogen content in soils from a fallow wheat rotation than those from other crop rotations (Sharma and Singh, 1970). The maximum amount of available nitrogen content in T 6

may be attributed to the effect of legumes particularly berseem because of its long growing period, high plant density, intense and active nodulation and constant sloughing off of the root nodules and the consequent incorporation of a high amount of biomass rich in nitrogen. It may also be because the fertilizers directly contributed towards the available nitrogen pool and that this enhanced the decomposition of the organic nitrogenous materials. It has been reported (Sharma and Singh, 1970) that, among


the legumes, berseem showed maximum increase in available nitrogen content thus confirming the finding of this experiment.

The doses of fertilizer N, P and K applied to different treatments during the whole of the experimental period are given in Table 1. High- est and lowest amounts of fertilizers were necessary in the treatments T 4 (rice-potato-onion) and T~ (rice-wheat-fallow) respectively. The values of correlation coefficients ('r' values) between the amount of fertilizer N, P and K used and available N, P and K after the end of experiment were 0.5584"*, 0.4421"* and 0.6958** respectively. Statistically significant correlation coefficients for N, P and K indicates an important role of crop plants in recycling the nutrients from deeper soil layers to the surface layer.

Balance sheet of major soil nutrients"

The balance sheet of major nutrients presented in Table 5 showed a positive balance for available nitrogen. The maximum positive balance of 43 kg ha 1 was obtained in T o (rice-berseem- fallow) and the lowest positive balance was obtained in T~ (rice-wheat-fallow) and T 4 (rice- potato-onion) i.e. 28kg ha J. The maximum positive balance of nitrogen was through using legumes in a crop rotation. Similarly in the case of T 5 (rice-mustard-moong), which received a positive gain of nitrogen of about 39 kg ha -~. The positive balance is most favourable in treatments having legumes (rice-berseem-fallow; rice- mustard-moong). The rotation of cereal crops exhausts the nitrogen status of the soil and hence a less positive nitrogen balance was obtained. The balance of phosphorus was always positive and all the treatments ranged from 1.5 to 11.3 kg ha-~. The lowest positive phosphorus balance of

Table 5. Balance sheet of nitrogen, phosphorus and potassium under different crop rotations over a period of two years

Treatments Nitrogen (kg ha ~) Phosphorus (kg ha 1) Potassium (kg ha ~)

Initial Final Balance Initial Final Balance Initial Final Balance

T~ 302 330 28 41 42.5 1.5 375 335 40 T 2 302 339 37 41 29.7 1.3 375 300 75 T 3 302 326 24 41 39.5 1.5 375 325 50 T~ 302 330 28 41 46.7 5.7 375 350 25 T 5 302 341 39 41 31.7 9.3 375 332 43 T 6 3(/2 345 43 41 37.7 3.1 375 325 50

256 Prasad and Umar

1.5kg ha ~ was obtained in T~ (rice-wheat- fallow). Similar positive balance results were also reported for various rotations (Deka and Singh, 1984). The balance of potassium obtained was also positive in all the treatments. The maximum balance was obtained in T2 (rice-wheat-moong) followed by T5 (rice-mustard-moong) and the lowest positive balance was obtained in T 4 (rice- potato-onion). These results are in conformity with earlier findings (Deka and Singh, 1984). It has also been reported that the available potassium content also increased in control plots after 19 crops (Prasad and Sinha, 1981).

Available Zn, Cu, Mn, Fe status of soil

The data on available Zn, Cu, Mn and Fe after two cycles of fixed crop rotations are presented in Table 6. Table 6 also indicates the initial and final values of micronutrients present at the end of the experiment along with gain (+) and loss ( - ) of nutrients. From Table 6 it is evident that available Zn, Cu, Mn and Fe content of soil under various treatments varied from 0.23 to 0.42, 3.16 to 4.18, 12.57 to 18.00 and 47.69 to 51.25 ppm respectively. The data on available Zn indicate that there is a considerable decrease in the available Zn status, from its initial value, as a result of two crop cycles of fixed crop rotation. It is evident from Table 6 that the available Zn was less, where higher doses of fertilizers were applied as well as on the plots under a high intensive cropping system. The maximum loss ( - ) of 1.18 kg ha ~ Zn was reported from the treatment T 4 (rice-potato-onion). The loss of Zn varying from 0.51 to 0.9kg ha -~ has already been reported from a wheat-maize rotation and from 0.47 to 12.34 kg ha -~ from wheat-groundnut rotations (Takkar et al., 1971). The available copper content of the soil ranged from 3.16 ppm to 4.18ppm the lowest in T~ (rice-wheat-moong) and T4 (rice-potato-onion) and highest in T~ (rice-wheat-fallow). Almost all the treatments showed an increase in available Cu content of soil from the initial value. Available Mn content of the soil increased up to maximum in T3 (rice- gram-rice) treatment, from the initial value, but showed a net gain (+) of 3.20kg ha -~ due to being waterlogged for a greater part of the year in this treatment, whilst the rest of the treat-

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Table 7. Correlation ceofficients (r) for relationship between organic carbon and available micronutrients, pH and available micronutrients

Property Correlation coefficient (r)

Organic carbon and zinc -0.59 Organic carbon and copper -0.24 Organic carbon and iron 0.57 Organic carbon and manganese -0.42 pH and zinc -0.33 pH and copper -0.09 pH and iron -0.19 pH and manganese 0.88 ~'

~' Significant at 5% lever.

ments showed a loss ( - ) of available Mn content. Available iron content of the soil varied from 47.69ppm to 51.25ppm. The maximum loss ( - ) of 1.48kg ha -a was recorded in T 2 (rice-wheat-moong) and the lowest (0.18kg ha - l ) in T~ (rice-wheat-fallow). The rest of the other treatments showed the net gain (+ ) maximum 5.64kg ha -~ in T 6 (rice-berseem-fallow) and the lowest 1.38 kg ha -1 in T s (rice-mustard- fallow). Relationships between available micronutrients (extracted by DTPA) and organic carbon, pH and available micronutrients are presented in Table 7. From Table 7, it is clear that available micronutrients did not correlate significantly with soil organic carbon. Further, the available micronutrients, except available Mn, did not correlate significantly with soil pH in- dicating that their extraction by DTPA solution (buffered at pH 7.3) is not dependent on soil pH in the neutral range. Similar results have been reported (Kanwar and Randhawa, 1974). Thus soil reaction alone cannot be used to explain the response to these nutrients in soil. Hence the effect of soil reaction on the availability of nutrients in soil cannot be generalised and needs further investigation.

Conclusion

Thus, it may be emphasised that to enhance and to maintain the proper fertility status of the soil under various cropping sequences, the incor-


poration of leguminous crops, and the proper use of balanced chemical fertilizers, along with micronutrients, are necessary. These are essen- tial for maintaining yield under various multiple cropping system.

Acknowledgement

The authors wish to express their gratitude to Dr R D Singh, University Professor-cure-Chief Scientist (Agronomy), Agricultural Research In- stitute, Patna, for his supervision of field experi- ments.

References

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Ahlawat I P S, Singh A and Sarof C S 1981 Effect of Winter Legumes on economy and productivity of succeeding cereals. Exp. Agric. 17, 57-62.

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258 Effect of crop rotations on yield

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effect of rice based six multiple cropping sequences under two cycles of crop rotations on yield and...

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