Boron application influenced growth, yield and fiber quality of upland cotton (Gossipium hirsutum L.) under different irrigation regimes

Cotton is a major imperative cash crop crop globally including Pakistan. Among abiotic stresses, drought stress is critical that suppress plant growth, reduce crop production, low fiber quality and poor earnings for farmers. Nutrient deficiency is major factor resulting in poor crop production. Sufficient nutrient application has better capability to increase yield because it helps to plants to stand against adverse climatic conditions within the growing areas. Therefore, present study was conducted on evaluation of cultivars performance applying numerous irrigation systems and use of boron through different methods. Cultivar CIM-678 had maximum growth traits, allometry parameters and fiber quality attributes than CIM-602 which had minimum growth, allometry and fiber quality traits. Foliar application of boron and field capacity (75%) also increased plant growth, allometry and fiber traits. The interactive effects of cultivars, boron use and field capacity were improved the plant growth, yield, allometry parameter and fiber quality traits. Conclusively, CIM-678, boron foliar spray and field capacity (75%) improved the cotton crop production with excellent fiber quality traits.


Introduction
Cotton is more popular as "white gold" because of higher economic potential in tropical and subtropical regions including Pakistan. Generally, textile industry mainly based on natural fiber for different mankind purposes Photosynthetic imbalance, disturbance of electrolyte leakage, respiration impairing, poor accumulation of carbohydrates, imbalance ion exchange, cell division restriction and nutritional metabolism [9, 10]. Consequently, it is more urgent and time need to situate more efforts aimed at improvement of cotton with excellent traits by using several drought resistant cultivars, better management practices, sufficient nutrition management and numerous cultural practices. Numerous physiological changes were occurred in plants under drought stress. Nutrient deficiency in plants may possibly be occurred because of soil compaction, excess fertilization and intensive cropping systems [11,12]. Exogenous application of different macronutrients and micronutrients had better potential to increase crop production. Moreover, these have potential to increase enhance plants defense mechanism against different biotic and abiotic stresses especially against drought stress [1]. Deficiency of different micronutrients such as manganese, copper, sulfur, boron and zinc is found to be more common in agronomic crops in developing countries [13]. Many improvements in nutrition management are necessary for increase of cotton production with good quality fiber traits [14]. Several earlier research work proved that application of different nutrients especially boron increased plant defense mechanism and reduce drought stress conditions resulting in better performance of cotton yield Pickings were start at 04 -11-2017 and 07-11-2018. Several pickings were harvested after one week interval. Treatments Two cultivars i.e. CIM-678 and CIM-602 were studied. Boron was applied through different methods i.e. applied in soil (B1), treated the seeds (B2) and foliar spray (B3). Moreover, three irrigation regimes i.e. 75 % field capacity (I1), 50 % field capacity (I2) and 25 % field capacity (I3).

Observations Agronomic traits
Twelve plants were used from each treatment for estimation of plant height, number of bolls/ plant, boll weight, seed cotton, lint and biological yield, and seed cotton harvest in the current study. Leaf area duration was calculated by LAI1 and LAI2 with leaf area indices at times T1 and T2 and LAD (days) = (LAI1 + LAI2) × (T2-T1)/2 [1]. Crop growth rate was calculated from weighed samples of 10, 30, 60 g of green leaves, stalks and bolls collected from all the studied treatments and samples were dried at 80 °C. Net assimilation rate was determined from formula as determined [1]. Fiber quality traits Fiber traits such as fiber length, elongation, uniformity, strength and micronair were calculated using High Volume Instrument (HVI Spectrum).

Data analyses
The collected data were separated using Statistix 8.1 software through analysis of variance technique under three way factorial [12]. LSD test was used for means separation under 5% probability [10].

Figure 3. Leaf area index, leaf area duration and net assimilation rate as affected from cultivars, boron application and field capacity
As regards fiber quality parameters, CIM-602 cultivar had higher fiber length (30.56 mm) than CIM-678 (20. 78 mm). Among boron application, foliar application showed higher fiber length (24.44 mm) than other studied boron application methods. Among irrigation regimes, field capacity (75%) showed significant higher fiber length (27.72 mm) than field capacity (25%) (159.22 cm). The combination of cultivars, boron use and irrigation regimes for fiber length were presented in (Fig. 4). CIM-602 had greater fiber elongation (30.47) than CIM-678 (30.38). Foliar application of boron showed higher fiber elongation (30.41 mm) than other studied boron application methods. Among irrigation regimes, field capacity (75%) showed greater fiber elongation (30.42 mm) than field capacity (25%) (30.36 mm). The interface of cultivars, boron use as well as irrigation regimes for fiber elongation were presented in (Fig. 4). CIM-602 had maximum fiber uniformity (30.47 mm) than CIM-678 (30.32 mm). Application of boron as foliar showed higher fiber uniformity (30.47 mm) than other studied boron application methods. Among irrigation regimes, field capacity (75%) showed greater fiber uniformity (30.41 mm) than field capacity (25%) (30.38 mm).
Interaction of cultivars, boron use as well as irrigation regimes for fiber uniformity were presented in (Fig. 4). CIM-602 had higher fiber strength (25.22 mm) and micronair (4.15 µg/inch) than CIM-678. Foliar application of boron showed maximum fiber strength (25.22 mm) and micronair (4.15 µg/inch) than other studied boron application methods. Among irrigation regimes, field capacity (75%) showed greater fiber strength (21.39 mm) and micronair (4.04 µg/inch) than field capacity (25%). The interaction of cultivars, boron application and irrigation regimes for fiber strength and micron air were presented (Fig. 5). Cost benefit ratio was determined in cotton crop (Table 4).

Discussion
CIM-678 had maximum growth traits like plant height, boll weight, bolls number/plant, lint yield, seed cotton yield, seed cotton harvest than cultivar CIM-602. Allometry traits such as leaf area index, leaf area duration and net assimilation rate were higher in cultivar CIM-678 than CIM-602. Fiber quality traits i.e. fiber length, elongation, uniformity, strength as well as micronair were greater in cultivar CIM-678 as compared to CIM-602. Between cultivars, CIM-678 had excellent growth, allometry and fiber quality traits. Current study results are under conformity to earlier research work because the cultivars showed variation due to their diverse genetic makeup [16,17]. Among boron application methods, foliar application of boron showed higher plant height, boll weight, bolls number/plant, lint yield, seed cotton yield and seed cotton harvest. Boron spray on leaf enhanced allometry traits comprising leaf area index, leaf area duration and net assimilation rate. Fiber quality parameters containing fiber length, elongation uniformity, strength and micronair were improved in the current experiment. Micronutrients spray on leaf is important source to increase the growth, allometry and fiber quality [18]. Leaf sprays are quickest source of nutrients absorption used for food synthesis because leafs are major factories for food synthesis [19]. Different researcher focused on boron application through and soil and seeds treatment. However, foliar application of boron is very negligible in developing countries especially in Pakistan.