IntroductionIn semiarid tropical locations, polyhalite (K2Ca2Mg(SO4)4H2O) and muriate potash (KCl) were tested for their ability to increase cane growth, yield, and recovery at potash (K)- and calcium (Ca)-deficient sites.MethodsThe treatments involved control plots with no potash fertilizer (T1); T2 and T3 applied potassium through (muriate potash) MOP only at 80 and 120 kg K2O ha−1, whereas T4 and T5 applied potassium with half of MOP and polyhalite at 80 and 120 kg K2O ha−1, respectively.Results and discussionAt 35 days after harvest (DAH), T2 (10.82%), T3 (24.1%), T4 (34.9%), and T5 (34.9%) had a greater ratoon resprouting rate than did the control treatment, where it was just 37.0 out of 100 harvested canes. At 308 DAH, T2 (−5.9%), T3 (−5.7%), and T5 (−6.6%) presented greater leaf chlorophyll contents than did T1. The K-fertilized plots yielded 64.31 t ha−1 in T2 and 65.97 t ha−1 in T5, whereas the control plot yielded 61.5 t ha−1. Compared with the control plots, the T5 plots experienced fewer stalk borer (−28.6%), top borer (−23.3%), and early shoot borer (−23.3%) attacks. T2, T4, and T5 presented higher percentages of commercial cane sugar (CCS) (6.82, 8.83, and 8.74%, respectively) than did the control plots. T1 and T3 had similar CCSs (10.99 and 11.33%, respectively). The CCS weight per area ranged from 7.98 to 8.47 t ha−1 near maturity. T4 (8.59 t ha−1) and T5 (8.60 t ha−1) had significantly greater values than did T1–T3. Compared with the control, the applied potassium fertilizer increased the economic output by 8,711, 11,687, 13,485, and 13,857 INR ha−1 in the T2, T3, T4, and T5 plots, respectively. The higher cost of polyhalite than MOP has reduced its economic advantages. Thus, the T4 plots outperformed the other treatments in terms of growth, yield, and quality indices, but their higher values (120 kg K2O ha−1) were statistically equivalent.ConclusionFinally, the study concluded that MOP and polyhalite at a 50% ratio of 80 kg K2O ha−1 may help improve sugarcane growth, yield, and quality in semiarid tropical locations.

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).

Polyhalite is a hydrated sulphate evaporate mineral containing potassium, sulphur, calcium and magnesium that crops require in significant quantities but has limited evaluation as a fertilizer for sugarcane.The sugarcane crop has a high demand for potassium for better quality. To keep the above facts in mind, the present experiment was conducted to evaluate the effect of polyhalite and muriate of potash (MOP) on the quality attributes of sugarcane var. Co 11015 (Atulya) in sandy loam soil at Arachalur, Erode district. The experiment was laid out in a randomized block design consisting of ten treatments. The treatment included were T1 –control, T2 - 50% K as MOP, T3 - 100% K as MOP, T4 - 100% K as Polyhalite, T5 - 100% K (1:1 ratio of Polyhalite and MOP), T6 - 100% K (1:3 ratio of Polyhalite and MOP), T7 - 150% K as MOP, T8 - 150% K as Polyhalite, T9 - 150% K (1:1 ratio of Polyhalite and MOP), T10 - 150% K (1:3 ratio of Polyhalite and MOP). The application of potassium fertilizers in different levels and ratios significantly (5%) influenced the quality attributes of sugarcane. The results of the experiment revealed that the application of 150% K (169.5 kg K2O ha-1) as polyhalite (T8) recorded maximum brix, pol, purity, CCS%, and extraction% and also this treatment was recorded minimum reducing sugar and fibre%. The present experiment would be helpful to sugarcane farmers for quality improvement through the application of polyhalite as a potassium fertilizer.

Balanced fertilizer management promotes plant growth, enhances produce quality, minimizes inputs, and reduces negative environmental impacts. Wax gourd (Benincasa hispida) is an important vegetable crop species in China and in South Asia. Two crop nutrition options, NPK and the natural mineral polyhalite, were tested, separately and combined, with the aim of enhancing wax gourd yield and quality and simultaneously to increase nutrient use efficiency and reducing inputs. The experiments tested the optimization of NPK by reducing the proportion of phosphorus (P), and the effect of enriching the soil with essential macronutrients by the use of the supplementary mineral fertilizer polyhalite containing magnesium (Mg), calcium (Ca) and sulfur (S). Two experiments were carried out in Foshan County, Guangdong, China, in 2018 and 2019. Experiments included four treatments: (1) Conventional NPK (15:15:15); (2) Optimized NPK (16:8:18); (3) Conventional NPK + polyhalite; (4) Optimized NPK + polyhalite. Fertilizers were applied prior to planting. While optimized NPK alone had no effects on fruit yield and quality, supplementary polyhalite resulted in a 10–17% increase in yield and significantly improved produce quality due to increased nutrient uptake from polyhalite, resulting in better foliar biomass. We conclude that the combined crop nutrition options improved yield and quality, enhanced nutrient use efficiency, and reduced risks of nutrient pollution. Inclusion of polyhalite in balanced fertilization practices as a supplementary source of secondary macronutrients seems promising. Nevertheless, plenty of space remains open for further adjustments of NPK application management, focusing on reduced rates, optimized ratio, and accurate timing of application for each nutrient.

Agriculture is the backbone of the Indian economy, in spite of concerned efforts towards industrialization in the last three decades. Therefore, the soil quality and fertility are the major factors in crop production. Declining soil fertility is one of the primary factors that directly affect crop productivity, and fertilizer-use is a key factor in order to keep soil fertility and productivity. A major factor in declining soil fertility is potassium (K) depletion, especially on smallholder farms where fertilization decisions are not based on regular soil testing. Most of the smallholder soybean producers do not have access and investment capacity to soil testing services. Therefore, there is a need to create K fertilizer recommendations based on empirically verified knowledge at India-specific scale. Such large-scale studies, in local filed conditions, are currently lacking. In order to bridge this gap, and generate proven set of directly applicable recommendations, a large-scale plot trial was launched; the Potash for Life (PFL) project. The study evaluated the K response in soybean when fertilizing with potash on K depleted soils in local variable field conditions. The aim was to (1) evaluate the effect and response consistency of K application on soybean yield, (2) to demonstrate to farmers the increased yield and profitability from K-inclusive fertilization regimes for this crop and give recommendations for transient yield increase, and (3) to raise the awareness among smallholder farmers about the importance of K fertilization. A comprehensive experiment was carried out in Madhya Pradesh (M.P.) and Maharashtra. The methodology was straight-forward; two identical plots side by side, with the only difference that one of them was fertilized with additional potash. The results showed a significant yield increase response from the potash application; the average yield increase was 244 kg ha-1 or 26 % in M.P., and 105 kg ha-1 or 36 % in Maharashtra. This entailed an average additional net profit of ₹ 6,681 INR ha-1 and ₹ 2,544 INR ha-1, in M.P. and Maharashtra respectively. It was concluded that the soil status of plant available K is significantly lower than the plant demand for soybean production in the two states, Consequently, K fertilization is necessary in order to improve agricultural practices and optimizing yields. Ultimately, following recommendations given in this study would allow farmers to generate additional profit, which could further allow them to invest in fine-tuning fertilizer practices through the means of soil testing.

Received : 17/05/2019 Accepted : 07/06/2019 Corresponding author: vijayamrutsagar@gmail.com Indian Journal of Fertilisers 15 (7) : 758-764, July 2019 Vijay Amrutsagar, Nilkanth More, Archana Pawar, Surinder Kumar Bansal and Patricia Imas All India Coordinated Research Project for Dryland Agriculture, Krushak Bhavan, 97, Raviwar Peth, Solapur, Maharashtra Potash Research Institute of India, Gurugram, Haryana International Potash Institute-Coordinator for India, Zug, Switzerland 2 2 Field experiments were conducted on dryland soils of AICRPDLA, Solapur for three years (2015-2016 to 2017-18) to evaluate the influence of different levels of potassium on kharif black gram-rabi sorghum cropping sequence in the randomized block design (RBD) for kharif black gram and split plot design for rabi sorghum. Grown in a sequence, kharif black gram and rabi sorghum responded significantly to the application of 20 and 50 kg K 2 O ha, respectively. Potassium application to both the crops sustained optimum levels of water soluble, exchangeable and non-exchangeable K in the soil which enhanced the K uptake and improved the moisture use efficiency over the farmers’ practice which exclude the application of K. Inclusion of K in fertilization schedule gave 38 and 9.5% higher yield in kharif black gram and rabi sorghum crops, respectively. Higher monitory returns and B:C ratio over the farmers’ practice were associated with application of potassic fertilizers.

Potassium is accumulated in substantial amount in water stressed plants, contributing to osmotic adjustment. Eight varieties of chickpea were field grown according to randomized block design with three replications during two consecutive crop seasons to explore the role of K uptake in drought tolerance of chickpea under rain-fed conditions. Plant water relation and other physiological parameters were measured at 70 days after planting, while potassium uptake and yield parameters were recorded at harvest. The varieties were divided into high (HKU), medium (MKU) and low (LKU) K uptake groups, using average K uptake across the seasons. All the data were statistically analyzed group-wise. The HKU, followed by MKU and LKU (i.e. HKU>MKU>LKU) gave the highest values for most of the parameters studied including seed yield and crop biomass. The HKU also exhibited the lowest osmotic potential together with maintenance of elevated water content and turgor in plants compared to MKU and LKU. There was significant season-group interaction regarding most parameters including seed yield and crop biomass. However, such an interaction was not significant regarding K uptake, though varietal group pattern of K uptake was similar to that of seed yield and crop biomass (i.e. HKU>MKU>LKU), indicating that promising chickpea varieties might be selected under rain-fed conditions using K uptake.

Turmeric (Curcuma longa) is a tropical rhizomatous crop. However, inadequate nutrient management and nutrient mining has led to low productivity of fresh rhizome yield in the major turmeric growing regions in South India. In order to study the effect of potassium and magnesium on turmeric production and on its quality attributes of the crop under conditions of adequate supply of nitrogen and phosphorus, a pot experiment was carried out on the Irugur soil series (Inceptisols) in the western zone of Tamil Nadu. The experimental design was a randomized block design with six treatments: K1 − control (no potash), K2 − (40a + 4b), K3 − (80a + 8b), K4 − (120a + 12b), K5 − (160a + 16b), K6 − (200a + 20b) (akg of K2O ha−1/bkg of MgSO4 ha−1) replicated threefold. The treatment (K6) recorded highest tiller count (14 plant−1), rhizome yield (963 g plant−1), and curcumin content (4.28%), which was statistically significant to all other treatments. These results suggest that the turmeric crop grown under intensive cropping systems requires large amounts of potassium and to certain extent requires magnesium for increasing productivity, enhancing quality, and for maintaining nutrient ratios in turmeric crop.

Potassium fertilization is uncommon in the North China Plain (NCP), especially in maize ( Zea mays L.) production. Our specific objectives in this study were to determine yield response to K fertilization as affected by conventional as well as high-yielding production practices. Seven field experiments were conducted in the NCP. The factorial study compared three levels of K fertilization (K0 = no K; K1 = medium K rate; K2 = high K rate) and two levels of production practices: conventional (CP) and high yielding (HP). At all sites, HP outperformed CP in terms of maize grain yield except at ZD in 2006. On average, maize grain yields were enhanced by 9.9 and 14.9% under CP and 15.7 and 21.0% under HP at the K1 and K2 levels, respectively. Maize yield response, as well as economic profit from applied K, were greater under HP than CP, on average, across seven site-years. Medium K inputs improved partial factor productivity (PFP) of applied N and P, while higher rates had inconsistent results. Overall, PFP and agronomic efficiency of applied K were improved under HP, as was the apparent recovery efficiency of applied K, which suggests positive interactions among K and other high-yielding production practices. Negative K balances were observed in all of the K0 and K1 treatments in both years and under both production practices, especially under HP. In intensive agricultural soils of the NCP with higher K content relative to South China, optimal K fertilization will improve soil fertility and support high grain yield.

Potassium fertilization is uncommon in the North China Plain (NCP), especially in maize (Zea maysL.) production. Our specific objectives in this study were to determine yield response to K fertilization as affected by conventional as well as high‐yielding production practices. Seven field experiments were conducted in the NCP. The factorial study compared three levels of K fertilization (K0 = no K; K1 = medium K rate; K2 = high K rate) and two levels of production practices: conventional (CP) and high yielding (HP). At all sites, HP outperformed CP in terms of maize grain yield except at ZD in 2006. On average, maize grain yields were enhanced by 9.9 and 14.9% under CP and 15.7 and 21.0% under HP at the K1 and K2 levels, respectively. Maize yield response, as well as economic profit from applied K, were greater under HP than CP, on average, across seven site‐years. Medium K inputs improved partial factor productivity (PFP) of applied N and P, while higher rates had inconsistent results. Overall, PFP and agronomic efficiency of applied K were improved under HP, as was the apparent recovery efficiency of applied K, which suggests positive interactions among K and other high‐yielding production practices. Negative K balances were observed in all of the K0 and K1 treatments in both years and under both production practices, especially under HP. In intensive agricultural soils of the NCP with higher K content relative to South China, optimal K fertilization will improve soil fertility and support high grain yield.

A two-year field study was conducted to determine the effect of two zinc (Zn) levels [0 and 10 kg zinc sulfate (ZnSO4) ha-1] in respect with four potassium (K) levels (0, 20, 40 and 60 kg K2O ha-1) on growth, yield and quality of forage sorghum. The soil of the experimental field was loamy sand (Inceptisol), carrying 70, 08, 77, and 0.51 mg nitrogen (N), phosphorus (P), K, and Zn kg-1 soil, respectively. Increasing K levels significantly improved most of the growth, yield, and quality attributes gradually irrespective of the Zn levels. Zinc applied at 10 kg ZnSO4 ha-1 proved significantly better than no zinc application at various K application rates. The benefit of zinc application increased progressively with increasing K rates for most of the parameters studied, indicating significant response of the crop to positive K x Zn interaction in plants in respect with K and Zn application to the soil. Accordingly, 60 kg K2O ha-1 applied with10 kg ZnSO4 ha-1 boosted most of the attributes maximally. It resulted in about 20-40% increase in growth attributes, 25% increase in fresh matter yield, 36-38% increase in dry matter yield, and 38% increase in protein yield compared to the comparable K level applied without zinc. It also enhanced N uptake by 38%, P uptake by 5-19%, K uptake by 40-42%, and Zn uptake by 114-144%. Across the K rates, application of 10 kg ZnSO4 surpassed no zinc application by 30-35% in N uptake, by 8-15% in P uptake, by 33-36% in K uptake, by 120-140% in Zn uptake, by 19-21% in fresh matter yield, by 29-31% in dry matter yield, and by 30-34% in protein yield.

Soybean is a major crop for oil and protein consumption by human, animal and fuel. The increased demand for oil and protein stimulated soybean production mainly by land expansion, with very modest growth in its productivity. With mounting pressure for environmental conservation and requirements for biofuels, there is a strong need for research and better crop management to increase its productivity. Soybean is part of many cropping systems with the advantage of supplying residual nitrogen to the following crop. Potassium not only improves yields but also benefits various aspects of quality (oil and protein content, larger seed size). Potassium increases nodulation in soybean’s roots and also provides resistance against pest and diseases. At present, average yield of soybean in India is 0.9 t/ha, which is much below the crop potential productivity. Low use of fertilizers and serious imbalances in the N: P: K application ratio are partially responsible for this low yield. Current fertilization rates are insufficient to sustain high yields and to replenish nutrient removal by the crop. During the last eight years, results from the joint IPI activities with Oilfed, Amlaha, RAK College, Sehore and NRCS, Indore in Madhya Pradesh clearly provide ample of data for improving potash recommendations. The results showed that yields of up to 2.5 t/ ha can be achieved and sustained with adequate K application. Increase in soybean oil and protein was also observed with optimum K nutrition, indicating improvement in crop quality. Field demonstrations also indicated that adequate K fertilization was highly profitable for farmers, 50 kg K 2 O/ha applied in split doses recorded the maximum net returns.

The experiments on research farm and farmers' field were conducted at NRC for Soybean, Indore and in nearby villages during 2003-04 to 2005-06 to assess the impact of balanced fertilization particularly of potassium nutrition on productivity of soybean as well as soybean-wheat cropping system under NRCS-IPI Project. Potassium application had significant positive effect on growth and nodulation in soybean. It favourably influenced the quality parameters of soybean as well. There was significant reduction in insect-pests infestation and disease incidence in soybean receiving potassium dressings. Application of 25 kg basal + 25 kg K 2O/ha at flowering (R 2 stage) gave maximum productivity of soybean-wheat cropping system while application of 25 kg K2O/ha as basal was most economical in terms of IBCR indicating the utility of K applications for resource poor farmers. The negative balance of K in all the treatments, except with the application of 75 kg K 2O/ha as basal to both the crops of the system, brought out the need for reorienting the present recommended levels of K to meet the system need and enhance system efficiency in sustainable way.

Line source sprinkling irrigation system was used to evaluate potassium (K) and other major osmolytes (sugars, proline, total amino nitrogen, and potassium) in respect with differential yielding capabilities of two groups of chickpea varieties (BR group with brown-red seed and PY group with pale yellow seed) under water deficit. Leaf water relation parameters, osmolytes, and total osmotic potential at full turgor (psi(pi 100)) were studied at early flowering (EF), late flowering (LF), and early fruiting (Eft) stages. Of the osmolytes, K accumulated in the highest amount (35 to 55% of the total psi(pi 100)) in chickpea leaves regardless of growth stages and varietal groups. Varietal groups showed substantial accumulation of SPN (sugars + proline + amino nitrogen) and K with the increase in soil moisture stress irrespective of growth stages, the BR group proving to be a better accumulator of the osmolytes than PY group in most cases. However, the contribution of SPN to total psi(pi 100) increased, while that of K decreased generally with increasing soil moisture stress, particularly at Eft stage. The OA capacity of BR varieties increased, while that of PY varieties decreased significantly at EF and LF stages along the line source moisture gradient. However, potassium-contribution to OA decreased largely with the increase in water deficit and crop age. In fact, it contributed negligibly to OA at the Eft stage in case of both the varietal groups. Osmotic parameters, namely, total OA and psi(pi 100) as well as psi(pi 100) due to SPN and K, correlated linearly (P <= 0.05 or P <= 0.01) with seed yield, relative water content, and drought tolerance efficiency under water deficit, indicating their significant role in drought tolerance of the crop. Since BR varieties proved generally superior to PY varieties regarding all the osmotic parameters, the superior yielding capability of BR to PY varieties (26-30% yield benefit under water deficit), could be ascribed to the favorable effect of osmotic parameters on the sustenance of crop yield under water deficit. Thus, chickpea varieties could be selected for improved drought tolerance on the basis of total OA, psi(pi 100) and psi(pi 100), due to osmolytes. Moreover, the psi(pi 100), due to K, could prove as a good selecting tool; however, further research is required to know if the chickpea varieties with high efficiency of K accumulation across the growth stages are able to withstand water deficit more efficiently.