​Effect of Different Crop Sequences on Soil Nutrient Status, Nutrient Uptake and Crop Yield in Western Himalayas of India

In India, a large number of crops are grown due to diverse agro-climatic conditions. At present, among cereal-based cropping systems, rice-wheat, rice-rice, pearl millet-wheat, maize-wheat and sorghum-wheat are the major cropping systems and occupy 85 per cent area. The continuous cultivation of these existing cropping systems resulted in reduced soil fertility and predominance of specific weeds (Katyal, 2003). Under the evolving agricultural scenario, crop diversification emerges as a major component for the sustainable production. In the peri-urban interface, the inclusion of high-value crops into the maize-based intercropping or sequential cropping systems proved to be profitable and remunerative (Singh, 2006).
       
Cropping systems, including crop diversification, intercropping etc. greatly impact soil health and quality. Usually cropping systems are designed to maximise yield putting strain on the available soil resources, but modern agriculture has become increasingly concerned about the sustainability of the system in order to attain long-term stable productivity (Vukicevich et al., 2016; Farigone et al., 2018). Since Indian agriculture seems to be influenced by the economic factors therefore to increase the income of the small households, to stabilize farm income and to conserve the natural resource-base, diversification of the existing systems is recommended. Sharma et al., (2012) and Mandal et al., (2016) have also reported that planting of suitable crop types in a system helps improve the soil nutrient status and also the microbial population. The selection of the crops needs to be planned to utilize the synergism among crops towards the efficient utilization of resources and to stabilise overall productivity, profitability and soil quality. Keeping this in view, the field study was conducted to assess the effect of different crop sequences on soil organic carbon, available N, P and K, nutrient uptake and crop yield.

Experimental site climate and soil type
 
In the present investigation, a field experiment was conducted during October 2018-October 2019 (Kharif and Rabi seasons) at an elevation of 1100 m amsl at a latitude of 32°04' N and longitude of 76°35' E at Bhadiarkar Experimental Farm, Department of Agronomy, CSK HPKV, Palampur, Kangra District of Himachal Pradesh, India. The soil of the experimental area falls in the order of Alfisols with Paleudalf as the great group as per the Udic Moisture Regime.
 
Treatment details
 
There were ten intensified cropping sequences examined under randomized block design with three replications viz., maize-wheat (T₁), maize-gobhi sarson + toria (T₂), dhaincha-cabbage-french bean (T₃), sunhemp-vegetable pea-french bean (T₄), maize + soybean-chickpea + linseed (T₅), rice-wheat + gram (T₆), hybrid sorghum + hybrid bajra-oats + aarson (hybrid) (T₇), hybrid sorghum + hybrid bajra-ryegrass + berseem (T8), babycorn-broccoli-french bean (T₉), okra-turnip-tomato (T₁₀). During kharif and rabi season the crop varieties were applied with the recommended dose of N, P₂O₅ and K₂O (Kg ha^-1). The source of nitrogen (N), phosphorus (P) and potassium (K) were urea, single super phosphate and muriate of potash.
 
Analysis of soil and plant samples
 
A composite sample (0-15 cm) of the experimental field was collected before the initiation of the field experiment for analysis. In order to study the chemical changes in the soil due to the cropping sequences, soil samples were collected from each plot after the harvest of the kharif and rabi season crops. The soil collected was then air dried, grounded and sieved through 2 mm sieve, labelled and stored for further analysis. The organic carbon was estimated by Chromic Acid Wet Digestion (Walkley and Black, 1934), available N by Alkaline potassium permanganate (Subbiah and Asija, 1956), available P by Olsen’s (Olsen et al., 1954) and available K by Ammonium acetate method (Metson, 1956). Plant samples were also analysed for N content using micro-kjeldahl method (AOAC, 1995), P and K content using wet digestion method (Koenig and Johnson, 1942; Black 1965, respectively). Analysis of soil for various physico-chemical properties in the sample collected before sowing have shown that soil was having Silty clay loam texture, soil being slightly acidic (pH 5.30), electrical conductivity 0.072 dS/m, status for organic carbon as 1.37 mg/kg, for available nitrogen 276.58 kg/ha, available phosphorus 34.28 kg/ha and available potassium 132.45 kg/ha.
 
Statistical analysis
 
In order to determine the effect of different cropping sequences on the soil nutrient status and yield analysis of variance (ANOVA) was used. The means were separated and compared through critical difference at 5 per cent level of significance under RBD.

Economic and maize grain equivalent yield
 
The crops in most of the treatments produced lower yields (Table 1) corresponding to their reported yields in the region except for maize, wheat, sorghum, bajra and linseed. The yield of the diverse vegetable crops supplanting the maize in kharif and wheat in rabi viz., okra, cabbage, vegetable pea, broccoli, turnip, frenchbean and tomato fluctuated from low to very low. The central reason for low yield in case of okra is the very high rainfall before and immediately after the sowing resulting in fluctuations in temperature. Similar trends were observed for seed germination in okra at high or low temperature conditions by Yusuf et al., (2001). The higher maize grain equivalent yield of 33,376 kg/ha was achieved under okra-turnip-tomato cropping sequence which was tailgated by baby corn-broccoli-frenchbean cropping sequence (25,375 kg/ha). Maize-wheat cropping sequence produced the lowest equivalent yield of 7,719 kg/ha. Okra-turnip-tomato gave 4.32 times higher equivalent yield in contrast to the traditional cropping system. The higher equivalent yields were owing to more tonnage of vegetable crops substituting the traditional crop (Table 2). The vegetables have a higher market price than the cereal crops which ended in higher equivalent yield as opposed to the cereal-cereal crop sequence. Mukherjee (2016) and Singh et al., (1979) observed similar trend for the equivalent yield in multiple cropping system over the traditional cropping system.
 

 

 
Effect on pH, electrical conductivity and organic carbon
 
Soil under different cropping sequences was analysed for their soil properties (Table 3) and no significant differences were observed in pH and organic carbon content. Electrical conductivity in surface soil ranged from 0.050-0.108 dS/m. The conventional cropping sequence, maize-wheat (T₁), resulted in the highest electrical conductivity (0.108 dS/m) while the lowest electrical conductivity (0.050 ds/m) was recorded under Maize-gobhi sarson + toria cropping sequence (T₂). Smaller amounts of soluble salts may be attributed to excessive leaching in lower soil profiles. EC in the normal range (0.05-0.70 dS/m) have also been reported by Loria et al., (2015) in Shiwalik hills.
 

 
Effect on available NPK
 
Soil samples were analysed to determine the initial as well as final nutrient status of the system and increase in available soil nutrients under the influence cropping sequence was recorded. In soil, mean values of available N, P and K ranged from 319.19-376.86 kg/ha, 40.56-48.57 kg/ha and 129.44-185.68 kg/ha (Table 4). The order of available nitrogen as affected by cropping systems was 376.86 kg ha^-1 under dhaincha-cabbage-frenchbean sequence followed by sunhemp-vegetable pea-frenchbean (371.27 kg ha^-1) and hybrid sorghum + hybrid bajra-ryegrass + berseem (369.59 kg ha^-1). Lowest available nitrogen of 319.19 kg ha^-1 was reported under rice-wheat + gram cropping sequence followed by the traditional cropping sequence, maize-wheat (320.45 kg/ha). Available phosphorous followed the order, Babycorn-broccoli-frenchbean sequence (48.47 kg/ha) followed by a hybrid sorghum + hybrid bajra-ryegrass + berseem sequence (46.81 kg/ha) of available phosphorus. The lowest available phosphorus of 40.56 kg/ha under maize-gobhi sarson + toria followed by maize + soybean-chickpea + linseed (41.33 kg/ha). Maize-wheat and rice-wheat + gram sequences showed almost similar available phosphorus (42.60 and 42.80, respectively) after the completion of experiment. Available potassium followed the order, 185.68 kg/ha under okra-turnip-tomato sequence followed by hybrid sorghum + hybrid bajra-oats + sarson (hybrid)(163.04 kg/ha) and babycorn-broccoli-frenchbean (154.57 kg/ha) sequence. The lowest available potassium was reported with dhaincha-cabbage-frenchbean and rice-wheat + gram, 129.44 and 132.91 kg/ha, respectively. Comparatively higher nutrient status was observed in soils under vegetable cropping sequence which may be attributed to regular additions of NPK fertilizers and organic manures.  Higher status of phosphorus status may be attributed to the fact the soils are slightly acidic in nature there by increasing the phosphorus reserves and making it available gradually. An intensive cropping system results in removal of nutrients from soil.
 

 
Effect on the uptake of nutrients
 
Nitrogen
 
Among cropping sequences (Table 4) sunhemp-vegetable pea-frenchbean recorded the highest uptake of the nitrogen (199 kg/ha) which was followed by okra-turnip-tomato cropping sequence (177 kg/ha) and babycorn-broccoli-frenchbean (146 kg/ha). The traditional cropping system, maize-wheat, showed the lowest uptake of nitrogen (59 kg/ha) followed by hybrid sorghum + hybrid bajra-ryegrass + berseem (60 kg/ha) sequence.
 
Phosphorus
 
Okra-turnip-tomato cropping sequence showed significantly highest uptake of phosphorus (70 kg/ha) which was tailgated by babycorn-broccoli-frenchbean and sunhemp-vegetable pea-frenchbean with 60 and 51 kg/ha, respectively. While the traditional cropping sequence, maize-wheat was at par with dhaincha-cabbage-frenchbean sequence in terms of the uptake with 44 kg/ha. The lowest uptake of the nutrient 21 kg/ha, was registered with the hybrid sorghum + hybrid bajra-oats + sarson (hybrid) while maize-gobhi sarson + toria and rice-wheat+gram cropping sequences were at par with each other with 22 kg/ha.

Potassium
 
The higher potassium uptake of 334 kg/ha was registered under sun hemp-vegetable pea-frenchbean which was followed by 265 kg/ha under babycorn-broccoli-frenchbean, dhaincha-cabbage-frenchbean (230 kg/ha) and okra-turnip-tomato (197 kg/ha) cropping sequences. The conventional cropping sequence, maize-wheat recorded the lowest potassium uptake of 50 kg/ha followed by 54 kg/ha under hybrid sorghum+hybrid bajra-oats+sarson (hybrid) sequence.
 
Balance sheet of nitrogen
 
All cropping sequences showed considerable loss in the available nitrogen (Table 5) except for the cropping sequence which included sunhemp-vegetable pea-frenchbean. The said sequence saw an increase of 166.37 kg/ha which might be due to the inclusion of green manuring crop followed by the leguminous crops in the subsequent seasons. The highest loss of available nitrogen to the tune of 247.49 kg/ha was recorded under maize-gobhi sarson + toria cropping sequence which was followed by rice-wheat + gram (195.93 kg/ha) and babycorn-broccoli-frenchbean (175.36 kg/ha) cropping sequence. Maximum removal of nitrogen may be attributed to greater production of biomass. Higher amounts of nitrogen fertilizer doses are to expect from the sequences which have net loss in the available nitrogen.
 

 
Balance sheet of phosphorus
 
There was a net loss of available phosphorus in all of the cropping sequences (Table 6). The highest loss of available phosphorus amounting to 84.71 kg/ha was recorded with rice-wheat + gram followed by 81.29 kg/ha under hybrid sorghum + hybrid bajra-oats + sarson (hybrid) and maize- gobhi sarson + toria (79.19 kg/ha) sequences. Besides the lowest decline was recorded under sunhemp-vegetable pea-frenchbean sequence (28.92 kg/ha) followed by okra-turnip-tomato sequence (38.66 kg/ha) which might be due to the multiple crops in the sequence.
 

 
Balance sheet of potassium
 
There was a net loss of available potassium in most of the cropping sequences (Table 7) except for those which had vegetable crops in their sequence. The maximum loss of 145.57 kg/ha was recorded under hybrid sorghum + hybrid bajra-oats + sarson (hybrid) sequence followed by maize-wheat (130.58 kg/ha) sequence. The sequence with a maximum gain was recorded under sunhemp-vegetable pea-frenchbean (165.57 kg/ha) sequence. This was followed by dhaincha-cabbage-frenchbean (97.84 kg/ha) and babycorn-broccoli-frenchbean (55.87 kg/ha) sequences.
 

 
Economics under different sequences
 
Cost of cultivation
 
Babycorn-broccoli-frenchbean with ₹ 308590.36 ha^-1 was the sequence with the highest cost of cultivation followed by sunhemp-vegetable pea-frenchbean, dhaincha-cabbage-frenchbean and okra-turnip-tomato sequences (₹ 280953.43 ha^-1, ₹ 267552.71 ha^-1 and ₹ 227849.81 ha^-1 respectively) (Table 8). Hybrid sorghum + hybrid bajra-oats + sarson (hybrid) recorded the lowest cost of cultivation (₹ 119639.64 ha^-1).
 

 
Gross and net returns
 
The highest gross returns of ₹ 566919.19 was recorded under okra-turnip-tomato cropping sequence. The lowest gross returns were recorded with the traditional cropping sequence viz., maize-wheat (₹ 155025.25 ha^-1). Okra-turnip-tomato recorded the highest net returns of  ₹ 339069.37 ha^-1. The lowest net returns were recorded under rice-wheat + gram sequence (₹ 25678.40 ha^-1). Mukherjee (2016) observed similar trends under cereal-vegetable cropping system.
 
Benefit cost ratio
 
Maize + soybean-chickpea + linseed cropping sequence recorded the highest BC ratio of 4.9 followed by 3.92 under okra-turnip-tomato and 3.87 under hybrid sorghum + hybrid bajra-oats + sarson (hybrid) sequences. The lowest of the ratio was recorded under the traditional cropping sequence viz., rice-wheat + gram (-0.05) followed by dhaincha-cabbage-frenchbean (0.56) which was at par with maize-wheat sequence (0.56). The intercropping in the sequences improved the BC ratio of some of sequences.

In terms of food for human consumption, highest yield was obtained under the okra-turnip-tomato cropping sequence followed by dhaincha-cabbage-frenchbean and sunhemp-vegetable pea-frenchbean. While in terms of fodder yield, highest was obtained under hybrid sorghum + hybrid bajra-oats + sarson (hybrid) cropping sequence followed by hybrid sorghum + hybrid bajra-ryegrass + berseem. Highest maize grain equivalent yield was obtained with okra-turnip-tomato crop sequence. All other treatments remained superior in comparison to the maize-wheat crop sequence. Maize + soybean-chickpea + linseed emerged to be the best treatment with the highest benefit cost ratio. The treatment comprising okra-turnip-tomato sequence also proved to be the second-best treatment followed by hybrid sorghum + hybrid bajra-oats + sarson (hybrid). Sunhemp-vegetable pea-frenchbean recorded the highest uptake of the available nutrients from soil which was followed by babycorn-broccoli-frenchbean. There was net loss of available nutrients although the loss was less in the sequences with multiple crops during the year. The treatments had no significant effect on the pH and organic carbon content of the soil.

No potential conflict of interest was reported by the author(s).