Abstract
Exhaustive crops such as cotton require potassium (K) in copious amounts as compared to other crops. High yielding cultivars in cotton-wheat cropping system, have further increased its demand in cotton growing areas of Pakistan. As cotton is grown in arid and semiarid areas, therefore often prone to water deficiency. The reproductive growth particularly flowering and boll setting are highly sensitive to low soil water potentials, where enough K supply can play a vital role. In this two-year field studies, three cultivars (early, mid and late maturing) were cultivated at two K fertilizer levels 100, 200 kg K ha−1 along with control with no K fertilizer application at two irrigation levels. In first irrigation level, water was applied as per full irrigation schedule, while in water deficit irrigation water was applied at deficit irrigation schedule started after flowering till harvesting. It has been revealed that K application has impact on boll setting as well as seed cotton yield, however early and mid-maturing cultivars are more responsive to K fertilization. Furthermore, irrigation level had significant impact against K fertilization and relatively better response was observed in deficit irrigation as compared to full irrigation. Nevertheless, fiber quality parameters were unaffected by K fertilization. Considering the best benefit cost ratio under water deficiency, it is concluded that 100 kg K2O ha−1 should be applied at the time of seed bed preparation for economical seed-cotton yield of early maturing Bt cotton.
Highlights
Increase in agricultural production is a great challenge that is affected by various biotic and abiotic stresses which can be mitigated to certain extent through nutrient management
As application of K fertilizer in cotton leads to increased boll weight, K fertilization is more important for early planting modern Bt cotton cultivars
The three cultivars were characterized based upon the traits such as days from sowing to first flower (DSFF), days from sowing to first boll (DSFB) and node number to first sympodial branch (NNFSB)
Summary
Increase in agricultural production is a great challenge that is affected by various biotic and abiotic stresses which can be mitigated to certain extent through nutrient management. K fertilizer use in cotton production in Pakistan is very limited causing further K mining from the soils and lowering K levels in soils[3,4]. Potassium, being involved in stomatal regulation and cell water relations, plays significant role in conferring drought resistance to plants under field conditions[5]. As application of K fertilizer in cotton leads to increased boll weight, K fertilization is more important for early planting modern Bt cotton cultivars. Potassium fertilization to early planting cotton cultivars results in increased boll weight and fruit bearing branches, while deficiency of K-fertilization can cause delayed maturation of bolls[12,13]. Deficiency of K affects reproductive growth of cotton, by reducing translocation of sugars, causing a decline in lint and boll weight, which reduces the yield[15]. The present study was conducted to investigate the agronomic response of Bt cotton cultivars differing in maturing periods to different K applications comparing water-sufficient and water-deficient field conditions
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