**6. Selection and variation for K-uptake in cotton germplasm**

In the area of genetic resource management, it is vital for sustainable cotton production to identify the genotypes of cotton for low K input. Production costs and management of K resources in agro environments would be reduced. Cultivation of nutrient-efficient crop genotypes is an effort to improve the efficiency of fertilizer usage [37] and decrease input costs and nutrient waste [17].

Categorization of cotton cultivars based on their growth performance under nutrient-deficient conditions is essential for the development of K-efficient cultivars in any crop. Soil worldwide is exhausting for the supply of adequate potassium (K) nutrition due to intensive crop cultivation systems. Exploiting genetic variability underlying an efficient K transport system is a viable, cost-effective strategy to increase cotton productivity in low-input production systems [12] stated during his experimentation to characterize 46 diverse cotton cultivars for enhanced K acquisition and utilization efficiency at low (0.26 mM K) and adequate (3.33 mM K) K levels in a sand culture experiment. There exists genetic variation in cotton cultivars for K acquisition and utilization. The Indicators such as DMYI and KUE, based on the mean and standard deviation, can be reliably used for the classification of indigenous cotton germplasm. The cotton cultivars including MNH-886, CYTO-124, FH-142, CIM-554, CIM-707, and IUB-2013 were found to be highly K-efficient and responsive. These cotton cultivars have a great potential for wider adaptation under both low and high-K input agriculture systems and, therefore, may be recommended for cultivation in soils.

Supply of adequate plant growth K improved significantly by 21–50% the growth characteristics of cotton and the yield of seed cotton from five cotton genotypes

#### *Enhancing Water Use Efficiency by Using Potassium-Efficient Cotton Cultivars Based… DOI: http://dx.doi.org/10.5772/intechopen.112606*

being observed, including symposia branch number (21%), leaf number (34%), dry biomass with leaves (30%), dry biomass shoot (31%), boll number (50%) and cotton yield (92%). In four cotton cultivars for biomass production and partitioning between various organisms under the K fertilization impact, [133] observed significant differences [81] also reported the differential reaction of two K<sup>+</sup> conventional cotton cultivars to two Bt and discovered that, because of decreased K<sup>+</sup> absorption, the Bt-transgenic cotton cultivars were more vulnerable to the deficit than conventional cultivars. However, it is very preferable to select a wide variety of cotton genotypes to categorize their differential K absorption and use efficiency. Such grading might provide significant basic information to support cotton breeding efforts that achieve high efficiency of K-use.

The variations in the absorption and use of nitrogen [146] and potassium among cotton cultivars were also identified [147]. One of the major techniques for the sustainable strengthening of farming systems revealed by Ref. [148] is to use genotypic variations by selecting and identifying crop genotypes best adapted to unflavored soils using nutrients. In their growth response, K-uptake and efficiency associated substantially with shot dry weight were significantly different, indicating an essential function for the creation of biomass. Higher biomass accumulated in K levels in efficient cultivars in the absorption of K and efficiency. Because K is extremely mobile in plants, genotypic variations in K absorption were linked to alterations to K translocation across cells and the whole plant [37]. Bt-transgenic cotton cultivars tend to have an increasing interest in K fertilizers with the rising usage of transgenic cotton as documented by Ref. [149] as a result of a more sensitive contemporary K shortage than traditional cultivars [149]. Reported that high-yielding, early maturing, and determinant cotton cultivars are more sensitive to drought stress compared with indeterminate cultivars that mature later with small boll numbers and weight.

K-uptake efficient genotypes have special physiological mechanisms to achieve enough K-uptake and efficient genotypes can have a larger area for contact between the root and the earth with a greater root surface absorptive capacity to maintain the soil and root spread gradient according to [37] K-uptake efficient genotypes. In eight cotton cultivars under controlled conditions both in growing chamber and field environments, the genetic diversity in K absorption and application was investigated, that [69]. K-efficient cultivars outperformed the K-inefficient cultivars by 29 and 234%, respectively, for K (dry mass supplied by unit K fixation) productivity (dry mass per unit K accumulates) and K. Under field circumstances with soil-compatible K-deficiency, the K-efficient cultivars generated a 59% greater potential yield (dry weight for each regenerative organ). During blooming, boll development, and seed production stage, however, signs of K insufficiency appeared.

More efficient cultivars are expected to have a favorable influence on the environment in their use and use of soil nutrients because farmers may decrease their chemical use in agriculture and demand significant yields, where fertilizer efficiency can be constrained by chemical and biological responses, drying of topsoil, subsurface limitations, and/or the involvement of disease [37].
