ABSTRACT

Mustard (Brassica junica, Czern and Coss) along with gram (Cicer arietinum L.) is a good intercropping system in Northern India. Legume as an intercrop improves the fertilizer use efficiency especially that of N fertilizer. However, the information on gram + mustard intercropping system is meagre. Hence a field experiment was conducted during winter season of 1994-95 and 1995-96 on sandy loam soil of Varanasi. The experiment was laid out in randomized block design with three replications. The treatment comprised combinations of three row ratio of gram : mustard (2:1, 3:1 and 4:1) and three levels of nitrogen to mustard 1/3^rd, 2/3^rd and full recommended dose). Sole crops of gram and mustard were also taken for comparison. The results reveal that all the intercropping treatments recorded yield advantage over sole cropping. Gram + mustard intercropping in 4:1 ratio with full recommended dose of N to mustard resulted in maximum land equivalent ratio (1.19) and output-input ratio (3.3). Increasing levels of N significantly improved the silquae plant^-1, test weight, seed yield of mustard as well as LER in all the row ratio. This indicates that there was no marked contribution of nitrogen to mustard from gram.

INTRODUCTION

Gram (Cicer arietinum L.) is generally grown mixed with other winter crops in Northern India. Intercropping of gram with mustard (Brassica junica L. Czern and Coss) has been found more remunerative than a pure stand of either gram or mustard (Tiwari et al., 1992). Legume as an intercrop improves the fertilizer use efficiency (De, 1980). Introduction of soybean as an intercrop in maize has been reported to save 30-60 kg N ha^-1 (Sharma and Chaube, 1991). However, information on nitrogen requirement of gram and mustard intercropping is very scanty. Hence the present study was undertaken to find out N schedule for gram + mustard intercropping.

MATERIAL AND METHODS

A field experiment was conducted during post rainy seasons of 1994-95 and 1995-96 at Varanasi, India under limited irrigation. The experiment was laid out in randomized block design with three replications. The treatment comprised combinations of three row ratio of gram : mustard (2:1, 3:1 and 4:1) and three levels of nitrogen to mustard (1/3^rd, 2/3^rd and full recommended dose i.e. 90 kg N ha^-1). Sole crops of gram and mustard were also taken for comparison.

The soil of the experimental field was deep sandy loam low in organic carbon (0.31%) having pH 7.2, available N 213 kg ha^-1, P 11.4 kg ha^-1 and K 218 kg ha^-1. Gram (Avrodhi) and mustard (Vardan) were sown on 8^th and 13^th November in 1994 and 1995, respectively. Harvesting of gram was done on 3^rd and 7^th April, and that of mustard on 14^th and 16^th March in 1995 and 1996, respectively. The rainfall received during 1994-95 and 1995-96 was 60.5 and 122 mm, respectively.

Observations were recorded on five randomly selected plants in the net plot area. However, for nodule dry weight plants were taken from border rows. Illuminance was recorded by using Digital Illuminance Meter (TES-1332) at the mass flowering stage of mustard on clear day at 11.00 A.M. In the intercropping, measurement was done in the centre of two mustard rows at the top of the gram plants. Land equivalent ratio (LER) was worked out as per procedure proposed by Mead and Willey (1980). Gram yield equivalent and output-input ratio were calculated on the current market prices of gram and mustard.

RESULTS AND DISCUSSION

Nodule dry weight

Gram and mustard intercropping in al the row proportions showed decline in nodule dry weight of gram with increasing N application to mustard during both the years (Table 1). However, the differences were not significant. Pure crop of gram recorded maximum nodule dry weight and it proved significantly superior to gram + mustard (2:1) with 90 kg N ha^-1 given to mustard. Here it appears that being mobile in nature N applied to mustard might have moved to gram rhizosphere affecting the nodulation (Franco, 1977; Pal and Saxena, 1975).

Illuminance

High illuminance was recorded in sole crops during both the years (Table 1). However, in intercropping it significantly declined with decreasing row ratio except at 30 kg N ha^-1 in 3:1 and 2:1 gram + mustard intercropping. Increasing levels of N application to mustard also caused marked decline in illuminance reaching to gram canopy particularly in 2:1 row arrangement. This could be attributed to the increased vegetative growth of mustard at higher rates of N application which resulted in intercepting more solar radiation particularly in 2:1 and 3:1 row arrangements.

Table 1: Effect of different treatments on nodule dry weight of gram and illuminance in sole and intercropping system of gram and mustard.

Yield attributing characters

Gram : Sole crop of gram produced maximum pods plant^-1 during both the years (Table 2). As compared to sole crop, pods plant^-1 declined significantly in gram + mustard intercropping except in 4:1 row ration. Strong positive correlation was observed between pods plant^-1 and illuminance. However, different N doses applied to mustard did not influence the pods plant^-1. The test weight of 100 grains also remained unaffected due to various treatments.

Mustard : Data presented in Table 2 show that various row arrangements did not affect much the yield attributes of mustard in both the years. However, siliquae plant^-1 and 1000 seed weight increased markedly with increasing levels of N application. Favourable effect of nitrogen on yield attributes of mustard has also been reported by Pradhan et al. (1994).

Table 2: Effect of different treatments on yield attributing characters in sole and intercropping system of gram and mustard.

Yield

Gram and mustard yields in the intercropping were significantly lower than their yields as sole crops in approximate proportion to their decrease in population in the intercropping (Table 3). Nitrogen applied to mustard did not influence the grain yield of gram but it improved the seed yield of mustard with increasing levels of N application. The difference between 30 and 90 kg N ha^-1 was significant in all the row arrangements during both the years. The results are in conformity with the findings of Pradhan et al. (1994).

Nitrogen economy

One of the objectives of the present investigation was to see the possibility of any reduction in the recommended nitrogen dose to mustard in the mixed stand. However, it was observed that nitrogen responded significantly to the maximum N dose i.e. 90 kg N ha^-1 (Table 2 and 3). Sinha et al. (1988) reported that gram plants retain the root nodules till flowering and afterwards the developing pods utilize the nitrogen fixed by the root nodules to a greater extent. By this time mustard, which is not very efficient user of nitrogen like cereals, attains maturity. So in the present experiment, no marked contribution of nitrogen fixed by gram was reflected on mustard.

Table 3: Effect of different treatments on yield of gram and mustard sole and intercropping.

Table 4: Effect of different treatments on gram yield equivalent land equivalent ratio (LER) and output-input ratio of gram and mustard sole and intercropping (average of 2 years).

N.A. – Not analysed ; Output-input ratio = Gross return ÷ Cost of cultivation.

Gram yield equivalent

All the intercropping treatments recorded higher gram yield equivalent than either of the sole crops (Table 4). In gram + mustard intercropping, gram yield equivalent increased markedly with increasing levels of N application to mustard. Application of 90 kg N ha^-1 to mustard produced maximum yield equivalent in 4:1 gram + mustard intercropping and it was closely followed by 2:1 row ratio with the same N dose. However, the pure crop of mustard produced lowest gram yield equivalent.

Land equivalent ratio (LER) and output-input ratio

Data presented in Table 4 reveal that though gram yield equivalent was markedly high in gram sole crop than mustard sole. However, the reverse trend was observed in output-input ratio. This can be ascribed to the better market price of mustard (US $ 37.2 q ^-1) and relatively low cost of cultivation (US $ 154.5 ha^-1) . The corresponding values for gram were US $ 25.6 q^-1 and US $ 175.2 ha^-1. While calculating the gross return, gram straw and mustard stover yield were also taken into consideration. However, gram + mustard intercropping was found to be more remunerative than either of the sole crops and recorded yield advantage ranging from 5 to 19%. Gram + mustard intercropping in 4 : 1 row arrangement with 90 kg N ha^-1 to mustard proved most advantageous recording output-input ratio of 3.30 and LER 1.1 9. It was closely followed by 2:1 gram + mustard intercropping with 90 kg N ha^-1 to mustard. However, 2:1 and 3:1 gram + mustard intercropping with 30 kg N ha^-1 to mustard could produce only 5% yield advantage.

REFERENCES

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