Crop Diversification of Cotton (Gossypium hirsutum) based Cropping System for High Resource Use Efficiency

Cotton is one of the most important fiber and cash crop of India and plays a dominant role in the industrial and agricultural economy of the country. In India, there are ten major cotton growing states which are divided into three zones, viz. north zone, central zone and south zone. North zone consists of Punjab, Haryana and Rajasthan. Central zone includes Madhya Pradesh, Maharashtra and Gujarat. South Zone Comprises Andhra Pradesh, Telangana, Karnataka and Tamil Nadu. In Andhra Pradesh Kurnool, Guntur, Anantapur are the major cotton producing districts.  Lower yields were recorded due to uneven opening of bolls and labour-intensive methods of cultivation, poor harvesting skills, lack of irrigation facilities, coupled with non-availability of quality seeds. Defoliation is an important management practice associated with high yields and high quality in cotton. It allows earliness in crop. Timely defoliant application leads to earliness in cotton with synchronous maturity, vacating the field 10-15 days earlier than the normal cotton. It paves way for introduction of short duration pulses like greengram in sequence. Thus farmers will get benefit of two crops in terms of production and profit instead of one long duration crop. Rotating cotton with crops less susceptible to the pests and diseases (i.e. wheat or pulses) in order to break the cotton/pest life cycle is also feasible. The inclusion of such crops will help to improve the economic situation of small and marginal farmers because of the higher income from such crops. Therefore, this study was carried out to determine the most productive, resource-use-efficient, remunerative and sustainable cropping system.

The experiment was conducted at Agricultural College Farm, Bapatla, which is situated in coastal region of Krishna Agro-Climatic Zone of Andhra Pradesh during kharif 2018-19and 2019-20. The soil of the experimental field was clay in texture, neutral in reaction, medium in organic carbon and low in available nitrogen, medium in phosphorus and high in available potassium during both the years. The experiment was laid out in Split plot design with four replications and nine treatments. The main plots were three defoliants viz., Dropp Ultra (Thiadizuron+Diuron) @ 250 ml ha^-1 (D₁), mepiquat chloride @ 100 ml ha^-1 (D₂) and Etherel @ 3000 ppm (D₃). The sub plots consisted of three times of applications viz., 80% boll opening (T₁), NACB - node above cracked boll (T₂) and NAWF- node above white flower (T₃) in kharif cotton. Cotton variety Suraj was sown on 07^thAugust 2018 and 5^th August, 2019 with a spacing of 60 cm×15 cm. Fertilizers @ 120 kg N, 60 kg P₂O₅ and 60 kg K₂O ha^-1 were applied due to high density planting of cotton variety, uniformly in the form of urea, single superphosphate and muriate of potash. Entire quantity of phosphorus was applied basally. Nitrogen and potassium were applied in three splits at 30, 60 and at 90 DAS. Recommended cultural practices and plant protection measures were followed throughout the crop growing season. Total number of fully opened leaves on main stem and branches were recorded before application of chemical defoliants and at alternate days interval of application up to 21 days after defoliant spray and calculated as the ratio of number of leaves present on the plant after spraying of defoliants to the number of leaves present on the plant before spraying defoliants and expressed in percentage. After picking of cotton in different treatments, the stubbles were removed. The experimental plots were not ploughed and the original layout was not disturbed during both the years of study. Pre-sowing irrigation was given after harvest of each treatment and paraquat was applied in those treatmental plots to arrest the regrowth of cotton stubbles. Sowing of greengram was done at three different dates, after picking of seed cotton only once as per the treatmental maturity. Seeds of greengram  were sown at a spacing of 30 cm×10 cm on 11-01-2019 in NAWF plots, on  20-01-2019 in NACB plots and on 03-02-2019 in 80 per cent boll opened plots during first year of study (2018-19) and on 07-01-2020 in NAWF plots, on 18-01-2020 in NACB plots and on 27-01-2020 in 80 per cent boll opened plots during second year of study (2019-20), respectively. Data was taken on plant height, drymatter production and yield.
       
System productivity in terms of cotton equivalent yield, land use efficiency and production use efficiency and economics were calculated.
   
The land use efficiency was worked out by dividing total duration of crops in individual sequence by 365 days and multiplied by 100 (Tomar and Tiwari, 1990). Production efficiency values were obtained by dividing total net returns and yield of a sequence by total duration of crop sequence (Tomar and Tiwari, 1990). Statistical analysis for the data was done following the analysis of variance technique for split-plot design as suggested by Gomez and Gomez (1984). Statistical significance was tested by applying F-test at 0.05 level of probability and critical differences were calculated for those parameters, which were found significant (p<0.05) to compare the effects of different treatments.

Performance of rabi greengram after cotton
 
Early termination of cotton was possible with defoliants applied at accurate time without compromising the cotton yield and quality, which facilitated sowing of next crop on the same land. In this experiment, different defoliants were tried at different times in kharif cotton. Then greengram was sown in the plots as and when the cotton crop was harvested. Residual effect of defoliants on greengram crop growth and yield was studied in terms of plant height, drymatter accumulation and haulm yield and seed yield during both the years of study.
 
Plant height (cm) of greengram
 
Plant height of greengram was not affected by defoliation treatment and times of application during both the years and in pooled data (Table 1). The interaction effect between these two factors was also found non-significant. During both the years and in pooled data, numerically the highest plant height was obtained in Etherel @ 3000 ppm applied in cotton as defoliant. As regards time of application, early sown crop i.e in node above white flower (NAWF) recorded maximum plant height during both the years and in pooled data, respectively.
 

   
Dry matter accumulation at harvest (kg ha^-1)
 
There were no significant differences in drymatter accumulation of greengram at harvest due to defoliants applied to previous crop during both the years and in pooled data. However, time of application exerted significant differences in drymatter accumulation of greengram. During first year of experiment, greengram sown in node above cracked boll (NACB-T₂) plots recorded highest drymatter and was found to be on par with early sown plots (T₃- Node above white flower (NAWF)  and superior over late sown plots (T₁- 80% Boll Opening) The same trend was observed during second year of experiment in 2019 and in pooled data.
 
Seed yield (kg ha^-1)
 
During both the years, among the various preceding defoliant treatments, the highest greengram seed yield was recorded under Dropp Ultra @ 250 ml ha^-1 which was on par with Etherel @ 3000 ppm and superior over Mepiquat chloride @ 100 ml ha^-1. In pooled data, D₁ (Dropp Ultra @ 250 ml ha^-1) was significantly superior over other treatments. During both the experimented years and in pooled data, Node above cracked boll (NACB) sown treatment recorded highest yield which was on par with early sown plots i.e node above white flower treatment which in turn was on par with  late sowing (T₁- 80% boll opening) treatment during two years of experiment and in  pooled data. Interaction between these two factors was found to be non-significant during both experimented years and in pooled data.
 
Haulm yield (kg ha^-1)
 
Preceding defoliants and its time of application at different stages had a significant effect on haulm yield of greengram (Table 2). The highest haulm yield was recorded under Dropp ultra @ 250 ml ha^-1 (D₁) which was significantly superior over Etherel @ 3000 ppm (D₃) and Mepiquat chloride @ 100 ml ha^-1 (D₂) during both the years and also in pooled data. With regards to time of application node above cracked boll (T₂) recorded highest drymatter which was on par with T₃ during 2018-19.
 

       
The same trend was followed in 2019-20 and in pooled data. Lowest haulm yield was obtained in T₁ plots which was significantly inferior over other treatments in 2018, whereas it was at par with T₃ (node above white flower) during 2019 and in pooled data. The interaction was found to be non-significant during the two years of study as well as in pooled data.
       
Greengram germination, plant height, drymatter and yield (seed and haulm) were not affected by residual defoliants. 90% defoliation and 80% boll opening was recorded with high rates of Dropp Ultra and Etherel, however no adverse effects was obtained either on cotton or greengram in sequence. This study suggested that, defoliants can be efficiently used (Dropp ultra and etherel) found to be safe for cotton- greengram sequence. These views confirm the previous findings of Foote et al., (2015) and Du Ming-Wei et al., (2013). Defoliants used in cotton (Thidiazuron + Diuron) did not show any detrimental effects on legume (clover and Austrian pea) as reported by Foote et al., (2015).
 
Total system productivity
 
The total system productivity in terms of cotton equivalent yield are presented in Table 3 and depicted in Fig 1. Data revealed that the total cotton equivalent yield was highest with Dropp ultra @ 250 ml ha^-1 (D₁) which was on par with Etherel @ 3000 ppm (D₃) during first year of experiment and in pooled data. During second year of study, dropp ultra alone recorded significantly highest total cotton equivalent yield. As regards time of application, (T₁) 80% boll opening recorded maximum total cotton equivalent yield which was on par with node above cracked boll during both the years and in pooled data, respectively. The lowest total cotton equivalent yield was obtained with node above white flower (T₃) during both the years and in pooled data. In 2019, it was found on par with node above cracked boll.
 

 

       
Cotton-greengram sequence in late sown (80% Boll Opening) treatment used the land for more period in a year having highest land use efficiency (LUE) of 66.0% and 64.7% during 2018-19 and 2019-2020, respectively followed by cotton-greengram (node above cracked boll) with 63.6% and 63.3%  LUE during both the years (Table 4).
 

       
Production use efficiency (Table 5) in terms of yield  and returns  was more in 80% boll opening during both the years, respectively. During first year of experiment node above cracked boll also had highest production use efficiency in terms of kg ha^-1 day^-1. These results were similar with Buttar and Singh (2013).
 

 
Economics of cropping system (cotton-greengram)
 
The highest gross returns, net returns and returns per rupee investment (Table 6) were noticed with application of defoliant Dropp Ultra @ 250 ml ha^-1 (D₁) and defoliants applied at 80% Boll Opening (T₁). These results are in conformity with the findings of Rajni et al., (2011) and Mrunalini et al., (2019).

Based on the study, defoliants applied to cotton had no adverse effect on growth and yield of greengram in sequence. Considering the system, cotton-greengram in sequence, defoliant dropp ultra gave highest total cotton equivalent yield, which was on par with Etherel. Application of defoliants at 80% boll opening noticed maximum total cotton equivalent yield and it was comparable with defoliants applied at node above cracked boll (NACB). Concluded that, instead of monocropping of cotton, we can go for cotton-greengram cropping system as it is productive and remunerative.

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