Sulphur (S) is the fourth major nutrient for cotton, and specifically S is involved in cotton seed quality. To understand the role of slow-release S bentonite formulations (Bensulf, FRT-Bensulf and micronized sulphur), examined the S mobility and sorption in five soil types of cotton-growing areas. Among the Sulphur (S) formulations, micronized S was superior to the grits of bensulf formulations ((Bensulf, FRTBensulf) with regard to S release.
In irrigated cotton – maize cropping system, nutrients applied through balanced form of chemical fertilizers along with farm yard manure (NPK + Mg + Zn + B + FYM) gave consistently better and enhanced seed cotton equivalent yield (2705, 2455 and 3109 kg ha-1) for the first, second and third years of continuous cropping system in Southern zone. Bt cotton variety (suraj) – maize cropping system registered the highest and stable seed cotton equivalent yield (3459 kg ha-1>) in third cropping sequence as compared to non Bt cotton variety-maize cropping system (2824 kg ha-1)).
Balanced form of inorganic fertilizers with FYM (NPK + Mg + Zn + B + FYM – once in two years) significantly enhanced the available nutrients like nitrogen (185 and 154 kg ha-1), phosphorus (21 and 22 kg ha-1), potassium (773 and 524 kg ha-1), sulphur (35.4 and 30.4 ppm) and zinc (1.49 and 0.63 ppm) in surface (0-30 cm) and subsurface (30-60 cm) layers of the soil respectively even after two years continuous adoption of cotton- maize cropping system, whereas the declined value of available nutrients (171 and 151 kg N ha-1, 19 and 18 kg P ha-1 and 746 and 505 kg K ha-1, 32.5 and 27.0 ppm S and 0.73 and 0.39 ppm Zn in surface and subsurface soil respectively) were observed in NPK applied plots.
Application of nutrients through organics (FYM 10 t/ha every year + Biofertilizer – Azophos + Neem cake 250 kg/ha + Sunnhemp incorporation) positively improved the organic carbon content in both surface (4.65 g/kg) and subsurface (4.10 g/kg) layer of the soil, however, soils receiving of no fertilizers and manures (3.60 and 2.95 g/kg) or getting of imbalanced chemical fertilizers (NPK only) (3.79 and 3.01 g/kg) continuously declined the soil organic matter content in both surface (0-30 cm) and sub surface (30-60 cm) layer of the soil respectively after two years of continuous cotton – maize cropping sequence.
In irrigated cotton-wheat cropping system, the highest seed cotton equivalent yield and system productivity (third cropping sequence) were observed in combined application of inorganic and organic sources of nutrients (NPK + Mg + Zn + B + FYM) (1706 kg ha-1 and 3985 kg ha-1) whereas the lowest was noticed in imbalanced chemical fertilizers ie., NPK only (1445 kg ha-1 and 3080 kg ha-1), organic source of nutrients (1051 kg ha-1 and 2494 kg ha-1) and control (681 kg/ha and 1785 kg/ha).
Visual difference of cotton crop between control (T1) and INM (T4) in non Bt suraj variety and organic sources of nutrient (T5) and INM (T4) in Bt suraj variety plot
Evaluation of nanoformulated micronutrients foliar spray for yield maximization in different cotton genotypes
The commercially available Nualgi nanofertilizer significantly increased the more seed cotton yield (15.8 %) than Nanomol, Agriklik and Richfield nanofertilizers. Fibre quality parameters like 2.5 % span length and micronaire value were also significantly affected by foliar application of Nualgi and Nanomol nanofertilizers. Moreover, the highest net return of Rs. 7100/- and Rs. 6381/- with marginal benefit cost ratio (MBCR) of 4.0 was produced by Nualgi and Nanomol nanofertilizers respectively followed by application of Agriklik and Richfield nanofertilizers with MBCR of 3.3 and 1.6 respectively.
Foliar application of 100 ppm of nano zinc oxide (50 nm) significantly increased the seed cotton yield than normal zinc source of nutrients like ZnSO4 and other nanoscale nutrients viz., nano FeO (<50 nm), nano CuO (40 nm) and nano MgO (50 nm). More than 10 per cent of seed cotton yield was assured by application of normal and nano form of oxide type fertilizers as compared to sulphate form of fertilizers. Moreover, fibre quality parameters like Uniformity ratio and fibre strength were improved by application of metal oxide nanoparticles than control. So, the nutrients like zinc, magnesium and copper proved that these nutrients can enable to derive the maximum genetic potential of fibre quality parameters of cotton.
Foliar application of normal recommended dose (100 %) of Nualgi with surfactant and Nanomol without surfactant showed the improvement in physiological parameters viz., nitrate reductase activity and reducing sugar content and yield parameters like number of opened bolls, boll weight and seed cotton yield than higher dosage (200 %) of nanofertilizers.
Among the single form of metal oxide nanoparticles like ZnO, MgO, CuO and Fe3O4, the highest average seed cotton yield was produced by foliar application of 50 nm of 100 ppm of zinc oxide (ZnO) nanoparticles. Likewise, among the combined form of metal oxide nanoparticles, foliar application of ZnO+MgO+CuO showed a significant increase in average seed cotton yield than other combinations of metal oxide nanoparticles. But, 45 % of more seed cotton yield was simply attained by foliar spray of 100 ppm of 50 nm ZnO nanoparticles than that of combined form of ZnO+MgO+CuO+Fe3O4 nanoparticles (35 %) over control. The performance of inorganic form of metal oxide nanoparticles either single or combinable were superior on increasing the seed cotton yield than combined sources of inorganic (metal oxide nanoparticles) and organic (seaweed liquid fertilizer) sources of fertilizers