Potassium is involved in a diverse range of processes within plants that are needed for their growth, yield and better quality. The polyhalite as a hydrated evaporate mineral that can be used directly as a source of potassic fertilizer. However, research on polyhalite's appropriateness and effectiveness, the present investigation aimed to evaluate the effect of polyhalite on growth, yield attributes, and yield of blackgram variety ADT 5 at Chinnakandiankuppam village, Vriddhachalam, Cuddalore district, Tamil Nadu, during 2021. The experiment was laid out in randomized block design consisting of ten treatments viz., T1 (absolute control), T2 (-K), T3 (12.5 kg K2O ha-1 as muriate of potash (MOP)), T4 (25 kg K2O ha-1as MOP), T5 (37.5 kg K2O ha-1 as MOP), T6 (50 kg K2O ha-1 as MOP), T7 (12.5 kg K2O ha-1 as polyhalite),  T8 (25 kg K2O ha-1 as polyhalite), T9 (37.5 kg K2O ha-1 as polyhalite), T10 (50 kg K2O ha-1 as polyhalite). The experiment revealed that the application of 37.5 kg K2O ha-1 as polyhalite (T9) significantly (5%) enhanced the growth attributes (plant height (38.7 cm), number of branches plant-1 (12.97), leaf area index (2.13), number of nodules plant-1 (18.76) and dry matter production (1972 hg ha-1), yield attributes (pod length (8.21 cm), number of pods plant-1 (20.05), number of seeds pod-1 (7.14) and test weight (3.53 g)) and grain yield (1439 kg ha-1), haulm yield (1876 kg ha-1) of blackgram. Thus the study would be helpful to farmers for yield maximization of blackgram through polyhalite as potassic fertilizer.

Polyhalite is a natural mineral which contains potassium (K2O, 14%), sulphur (SO3, 48%), calcium (CaO, 17%) and magnesium (MgO, 6%). It is used as fertilizer for high value crops. Soil fertility, selection of fertilizer sources and application practices are all crucial factors in maximizing mineral nutrition during the cropping season. With an increasing demand for fertilizer, polyhalite was identified as a potassium source for crops. In view of this context, a present experimental work was conducted during 2021-22 at farmer’s field, Arachalur, Erode district, Tamil Nadu, India to study the influence of polyhalite on growth attributes, yield attributes and yield of sugarcane var. Co 11015. The experiment was conducted in sandy loam soil laid out in randomized block design with 10 treatments replicated thrice. The recommended dose of nitrogen and phosphorus was applied uniformly to all treatments. The potassium was applied in two sources, muriate of potash (MOP) and polyalite in different ratios and levels except control. The results of the field experiment revealed that sugarcane significantly responded to the application of two potassium sources and levels. The maximum values of growth attributes like plant height, number of leaves per stalk, leaf area index, leaf chlorophyll content, yield attributes and yield like, number of internodes per stalk, length of internode per millable cane, length of millable cane, diameter of millable cane, single cane weight, number of tillers per plant, number of millable cane, cane yield and sugar yield were recorded with application of RDF (NP alone) + 150% K (169.5 kg K2O/ha) as polyhalite (T8). The lowest respond was found in the treatment T1, which received RDF (NP alone).