Effect of Potassium Nutrition on Potato Yield, Quality and Nutrient Use Efficiency Under Varied Levels of Nitrogen Application

A field trail was conducted during winter season of 2009–10 and 2010–11 at Central Potato Research station, Patna on sandy loam soil under irrigated condition to find suitable dose of potassium for potato cultivar Kufri Pukhraj for optimum yield, quality and nutrient use efficiency under different nitrogen levels. There was significant positive interaction between N and K. At each level of N, increasing levels of K application increased the tuber yield, N and K uptake by potato at harvest. Potassium and N application improved tuber size by increasing the large and medium grade yield and decreasing the small and very small sized tuber. Maximum yield of 39.83 t/ha was obtained when N and K was applied @ 225 kg/ha and 150 kg K₂O/ha against a tuber yield of only 14.36 t/ha without N and K application. The recovery efficiencies of K and N fertilizer on potato increased at 100 kg K₂O and 150 kg N/ha. There was less weight loss and rottage of tubers with potassium application whereas with increase in nitrogen levels there was increase in weight loss due to tuber rottage.

Potassium Buffering Characteristics of Ten Typical Rice Soils of Lesser Himalayas

An understanding of soil K dynamics is important for K management in a rice–mustard cropping pattern. Ten rice soils were evaluated for labile K (ΔK₀), K intensity (AR^K _e), change of K in solution (ΔK), equilibrium exchangeable K (EK₀), magnitude of conversion of solution K to exchangeable K (α) and potential buffering capacity of K (PBC^K). The 10 soils had exchangeable K values of 0.12–0.44 cmol_c kg⁻¹, with the lowest value in Telbal loam and the highest in Badripora clay loam. The highest ΔK₀ value (−0.356 cmol_c kg⁻¹) was observed in Badripora clay loam, and the lowest (−0.239 cmol_c kg⁻¹) was found in Kreeri clay loam. These soils exhibited equilibrium AR^Ke values of 0.8 to 3.1 × 10⁻³ mM^1/2, with the lowest value in Bonbagh clay loam and the highest in Ganasthan silt loam. The highest EK₀ value (0.853 cmol_c kg⁻¹) was observed in Kharpora clay loam and lowest (0.0.507 cmol_c kg⁻¹) was in Bonbagh clay loam. These soils also differed in the magnitude of conversion of solution K to exchangeable K(α), the highest value (32%) being seen in Ganasthan silt loam and the lowest (15%) in Dialgam loam. PBC^K ranged from 13.79 to 49.91 cmol_c kg⁻¹/mM^1/2. Future research is needed to calibrate the characteristics of K dynamics for soil fertility management and to predict how long a nonresponsive soil can meet crop K demand in rice–mustard and rice–wheat cropping systems.

Forms and Distribution of Potassium in Particle Size Fractions on Talc Overburden Soils in Nigeria

The potassium status of soils developed over talc overburden in a southern Guinea savanna of Nigeria was evaluated using exchangeable, acid extractable, total and residual potassium values in particle-size fractions. Soil samples collected from genetic horizons of six profile pits at Kampe Forest Reserve were separated into sand, silt and clay fractions. Exchangeable K, acid-extractable K, total K and residual K were determined in these fractions. Reserved K values were similar to those of mobile K, but lower than total and residual K, whereas exchangeable K showed the lowest values. Total K was >25 cmol kg⁻¹ in all the profiles; reserved K ranged from 9.26 to 24.45 cmol kg⁻¹ and mobile K ranged from 5.12 to 29.57 cmol kg⁻¹. Exchangeable K accounted for <1% of total K and ranged from 0.20 to 0.50 cmol kg⁻¹. In most cases, the clay fraction of the soils had the highest values for all potassium forms, followed by the silt fraction, while the sand fraction had the lowest values for these forms of potassium.

Effects of Leguminous Plant Residues and NPK Fertilizer Application on the Performance of Yam (Dioscorea rotundata ‘c.v.’ Ewuru) in South-Western Nigeria

The effects of cultivating and incorporating residues of previous tropical kudzu (Pueraria phaseoloides) and soybean (Glycine max) with application of NPK fertilizer on yam performance were evaluated at the teaching and research farm, LAUTECH, Nigeria. There were nine treatments: incorporation of legume residues (5 t DM ha⁻¹), application of recommended fertilizer rate for yam (90–50–75 kg NPK ha⁻¹) in the zone or 50% of recommended rate (45–25–37.5 kg NPK ha⁻¹), alone and in combination with residues and a control without residues or fertilizer in a randomized complete block design. Cultivation of previous legumes reduced soil nematode population (>200%) compared with no legumes. For both years, application of Pueraria residues improved tuber yield by an average of 15.8% compared with control. Fertilizer application enhanced arbuscular mycorrhizal (AM) colonization of yam roots but AM colonization was lower (50%) in plots where Pueraria residues were incorporated compared with other plots. Combined application of plant residues with fertilizer improved soil organic carbon, total N, exchangeable Ca and Mg compared with application of NPK fertilizer. From these results, it is concluded that half of the recommended NPK rate may be adequate and incorporation of residues with reduced NPK fertilizer application may be a sustainable soil fertility management option for continuous yam production.

Effects of Potassium Foliar Fertilization on Different Fruit Tree Crops over Five years of Experiments

Potassium (K) is an essential mineral nutrient for the fruit growth and quality. Foliar spray is starting to be used by fruit growers in addition to soil application or fertigation.

Different experiments were conducted over a period of 5 years on six fruit tree species, i.e., apple, pear, peach, olive, citrus and plum, in order to evaluate the effects of K foliar applications on the fruit growth, yield, quality and mineral status. Potassium as potassium sulfate was applied by foliar sprays several times according to the various critical growth stages of the fruits. Other treatments using fertigation or soil application were also included depending on the experimental designs.

The results showed different effects of foliar spray over the years. For fruit yield, the effect of K was significant only after 5 years of application for olive tree, but no effect was detected in peach and plum, whereas the improved yield was detected only after one year for citrus, apple and pear. Fruit quality was improved in most of the experiments, showing an increase in fruit weight and a higher soluble solid content.

Contribution of Nutrients through Critical Irrigation from Diverse Water Sources in Selected Watersheds of Semi-arid Tropical India

Critical irrigation is one of the most important management options to protect the crop during weather aberrations like dry spells at critical stages of the crop growth in semi arid condition. Various water harvesting structures are useful in watershed areas to cope up with mid-season droughts. These structures provide critical irrigations at sensitive crop growth stages by which they supply essential nutrients to some extent. We estimated the contribution of various sources of water in terms of plant nutrients and to what extent critical irrigations meet nutrient requirements of various crops. By giving 4 cm irrigation, the maximum major nutrient (kg ha^-1) addition in the studied watersheds is of the following order NO₃ (5.2, Kothapalli); SO₄ (15.2, Kolar); Na (72.0, Haveri); K (3.6, Govardhanapura); Ca (38.5, Semli and Shyamapura); Mg (20.5, Kothapalli) and for micronutrients (g ha^-1) Fe (109, Kolar); Zn (40, Kothapalli); Mn (90, Kolar); Cu (120, ICRISAT) and B (190, ICRISAT). Percentage of recommended dose of nutrients which can be met by three irrigations in cereal crops (5-10, 15-100, 10-20% in N,S,K respectively); legumes (5-30,10-100, 5-10% of N,S,K respectively); cotton (10-15, 25-30, 5-10% of N,S,K, respectively) and micronutrients such as Fe, Zn, Mn, Cu and B to the full extent. With the number of critical irrigations increased, application of secondary and micro nutrients should be avoided which otherwise leads to higher cost of alleviation and environmental pollution.

Potassium Fertilization Important under Dry Conditions

It is well known, that potassium is an extremely important nutrient for all agricultural and horticultural crops. Olaf Christen and Sebastian Damm from Halle University, Germany have recently demonstrated that potassium additionally has a number of positive effects on soil structure and soil water content. The yields of sugar beet increased especially under dry conditions. Additionally the water use efficiency (WUE) increased substantially. A high WUE is an important prerequisite for high yields under the dry conditions in the central parts of eastern Germany. The reason for this being an improved soil structure following a long term fertilization with potassium which improved the water availability and thus the early development of the sugar beet crop.

High K⁺ Supply Avoids Na⁺ Toxicity and Improves Photosynthesis by Allowing Favorable K⁺:Na⁺ Ratios through the Inhibition of Na⁺ Uptake and Transport to the Shoots of Jatropha curcas Plants

This study assessed the relationships between external K⁺ supply and K⁺ : Na⁺ ratios associated with Na⁺ toxicity in Jatropha curcas. Plants were exposed to increasing external K⁺ concentrations (6.25, 12.5, 25, 37.5, and 50 mM), combined with 50 mM NaCl in a nutrient solution. Photosynthesis progressively increased as the external K⁺ : Na⁺ ratios increased up to 0.75. The increase of photosynthesis and plant dry matter correlated positively with K⁺ : Na⁺ in xylem and leaves. The transport rates of K⁺ and Na⁺ from roots to xylem and leaves were inversely correlated. These ions presented an antagonistic pattern of accumulation in all organs. Maximum rates of photosynthesis and plant growth occurred with leaf K⁺ : Na⁺ ratios that ranged from 1.0 to 2.0, indicating that this parameter in leaves might be a good indicator for a favorable K⁺ homeostasis under salinity conditions. The higher K⁺ affinity and selectivity compared with Na⁺ in all organs associated with higher xylem flux and transport to shoots are essential for maintaining adequate K⁺ : Na⁺ ratios at the whole-plant level. These characteristics, combined with adequate K⁺ concentrations, allow J. curcas to sustain high rates of photosynthesis and growth even under toxic NaCl levels.

Corn and Soybean Tissue Potassium Content Responses to Potassium Fertilization and Relationships with Grain Yield

Research on relationships between K fertilization, crop yield, and tissue K concentration is needed for modern corn (Zea mays L.) hybrids and soybean (Glycine max L. Merr.) varieties. Twenty 2-yr trials with these crops in Iowa evaluated K effects on plant dry weight (DW), K concentration, and accumulation at the V5-V6 stage; leaf K concentration (R1 stage in corn and R2 in soybean); and grain yield, K concentration, and K removal. Five K rates (0–168 kg K ha^-1) were broadcast the first year (10 sites for each crop). Potassium increased corn or soybean yield at 16 site-years, which had soil K ≤ 173 mg K kg^-1 (15-cm depth, CH₃COONH₄ test). On average across first-year responsive crops, 91 and 103 kg K ha^-1 maximized corn and soybean yield, respectively, and across second-year crops the response was linear. Potassium fertilization increased grain K concentration and K removal to a greater extent and more frequently in soybean than in corn (10 vs. 5 site-years, respectively, for concentration and 11 vs. 3 site-years, respectively, for removal). The magnitude and frequency of responses for both crops were greatest for vegetative tissue K concentration and smaller (in decreasing order) for grain yield and K removal, grain K concentration, and early DW. There was large luxury K accumulation in vegetative tissues. Critical tissue K concentration ranges defined by two models were 20.2 to 25.1, 10.2 to 11.0, and 17.6 to 20.0 g K kg^-1 for corn plants, corn leaves, and soybean leaves, respectively, and could not be determined for soybean plants.

Field Correlation of Potassium Soil Test Methods Based on Dried and Field-Moist Soil Samples for Corn and Soybean

Soil K extraction with ammonium-acetate (NH₄OAc) from oven-dried samples is the most widely used K test method, but drying often increases extracted K compared with field-moist soil. This study assessed sample drying effects on soil K extracted by NH₄OAc and used field response data to correlate K tests based on dried (35–40°C) (DK) and field-moist (MK) samples for corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] based on 162 single- and multi-year response trials conducted during 6 yr (200 site-years for corn and 162 for soybean). Potassium (15-cm depth) extracted by DK was higher than for MK (on average 1.92 times higher). The ratio DK/MK decreased exponentially with increasing K (R² 0.77); increased linearly with soil clay, organic matter (OM), estimated cation exchange capacity (ECEC), and (Ca+Mg)/K ratio (r² 0.15–0.32); and increased with sample moisture but the relationship was poor (r² 0.03). The MK test correlated better than DK with grain yield response. The R² values for Cate–Nelson (CN), linear-plateau (LP), and quadratic-plateau (QP) models across crops were 0.24 to 0.27 for DK and 0.39 to 0.58 for MK. Critical concentration (CC) ranges for corn defined by these models were 144 to 301 mg K kg⁻¹ for DK and 51 to 82 mg K kg⁻¹ for MK; whereas for soybean were 136 to 283 for DK and 49 to 84 for MK. Potassium testing of field-moist samples predicts crop response to K fertilization better than the common test based on oven-dried samples.

Maize Nutrient Accumulation and Partitioning in Response to Plant Density and Nitrogen Rate: I. Macronutrients

Understanding nutrient balances in changing cropping systems is critical to appropriately adjust agronomic recommendations and inform breeding efforts to increase nutrient efficiencies. Research to determine the season-long P, K, and S uptake and partitioning dynamics in maize (Zea mays L.) as affected by low, medium, and high plant density (PD) and N rate factors and their interactions was conducted over four site-years in Indiana. Plant nutrient contents at maturity responded predominantly to N rate. Relative nutrient contents at silking compared with those at maturity were 47% for P, 100% for K, and 58% for S. Concentrations of P, K, and S varied less in leaf vs. stem (vegetative stage) and in ear vs. shoot (reproductive stage). Equivalent stoichiometric ratios were documented for N and S partitioning in leaf, stem, and ear components. The PD and N rate treatments did not modify P, K, and S nutrient partitioning to plant components during vegetative or reproductive periods (except for an N rate effect on leaf vs. stem P partitioning). Near silking, relative nutrient partitioning to the ear followed the order P > S > K. This mimicked the nutrient harvest indices observed at maturity, suggesting genetic modulation. Ratios of N to P, K, and S in whole-plant tissues were influenced by N content changes in response to N rate but not by PD. As the season progressed, PD and N rates changed the absolute P, K, and S quantities (primarily reflecting biomass responses) but had little influence on nutrient ratios.

Potassium Rate and Application Effect on Flue-Cured Tobacco

Research was conducted at two locations in 2009 and 2010 to evaluate the effect of various K rates and application methods on the yield and quality of flue-cured tobacco (Nicotiana tabacum L.). Treatments included five rates of K from sulfate of potash magnesia (0–0–22): 0, 84, 140, 196, and 252 kg K₂O ha⁻¹ that were applied: broadcast 1 mo before transplanting, broadcast 1 wk before transplanting, banded at transplanting, and a split application with one-half rate banded at transplanting followed by one-half rate banded at layby. Tissue samples were collected throughout the season at three separate growth stages: layby, topping, and after curing. Tissue samples were analyzed for total alkaloid and reducing sugars, N, P, K, and Mg content. Soil samples were collected the same day as K fertilizer application from plots not receiving supplemental K. Data were subjected to ANOVA using the PROC GLM procedure in SAS. Treatment means were separated using Fisher’s Protected LSD test at p ≤ 0.05. Application method and timing had no effect on any measured parameters; furthermore, crop yield and quality was not affected by K rates >0 kg K₂O ha⁻¹ at three of four locations. It is likely that early broadcast applications of K₂O with current rate recommendations would only be of concern with combinations of conditions that included coarse soil textures, low K indices, and/or excessive leaching rainfall.

Phosphorus and Potassium Fertilization Effects on Soybean Seed Quality and Composition

The effects of P and K fertilization on soybean [Glycine max (L.) Merr.] seed quality are unclear. Fertilization rates can have a positive effect on yield and composition in some growing locations and years but not in others. As the cost of soybean seed production increases, seed companies are interested in improving seed quality of soybeans possibly through increased soil fertilization. The objectives of this study were to determine the effect of different levels of P and K fertilization on soybean seed quality defined as seed viability, vigor, and seed composition. Seed samples were obtained from a long-term P and K fertilization trial. Phosphorus and K treatments were 0, 28, or 56 kg P ha⁻¹ yr⁻¹ and 0, 66, or 132 kg K ha⁻¹ yr⁻¹. Results indicated that excessive levels of P and K fertility decreased seed quality. Seed composition changed across sites and treatments, but changes were generally inconsistent. Total seed protein and oil were not significantly affected by P and K fertilization in most locations. However, linolenic acid concentrations increased with excessively high P and K fertilization while linoleic acid concentrations decreased only with P. These results indicate that excessively high levels of soil fertility may have negatively impacted seed quality.

Fertilizer Nitrogen Rate Effects on Nutrient Removal by Corn Stover and Cobs

The harvest of corn (Zea mays L.) stover and cobs for cellulosic ethanol production will likely accelerate the depletion of soil N, P, K, and S, thus increasing nutrient replacement costs. Fertilizer N rate is a management variable that may influence N, P, K, and S removed by corn cellulosic materials. The effects of fertilizer N rate on grain and cellulosic biomass yields have been reported for the Upper Midwest, but no information exists regarding its effects on stover and cob nutrient removal across a range of rates in diverse environments. Experiments were conducted in eight environments in Minnesota to determine the effect of fertilizer N rate on N, P, K, and S removal by corn stover (leaves, stalks, husks, shanks, and tassels) and cobs. Removal of N, K, and S by stover and cobs generally increased as fertilizer N rate increased, although the response often differed among environments. Removal of P by stover and cobs decreased or did not change as fertilizer N rate increased. Harvesting 7.5 Mg ha⁻¹ of corn stover removed on average 46, 3.5, 76, and 3.7 kg ha⁻¹ of N, P, K, and S, respectively, while harvesting 1.5 Mg ha⁻¹ of cobs removed 6.1, 0.37, 9.5, and 0.38 kg ha⁻¹ of N, P, K, and S, respectively. The harvest of solely corn cobs would remove 9 to 12% less N, P, K, and S, and thus deplete soil nutrient pools at slower rates compared with the harvest of both stover and cobs.

Effects of Cytokinin and Potassium on Stomatal and Photosynthetic Recovery of Kentucky Bluegrass from Drought Stress

Drought-induced stomatal closure may limit resumption of photosynthesis and plant growth if stomata do not quickly reopened when plants are later rehydrated. Cytokinins (CK) and K are known to regulate stomatal opening and closure. The objective of this study was to investigate whether foliar application of CK and K would enhance stomatal reopening and photosynthetic recovery in leaves of perennial grass after water deficit is alleviated. Kentucky bluegrass (Poa pratensis L. ‘Brilliant’) plants were subjected to drought stress by withholding irrigation for 15 d and then rewatered for 6 d in growth chambers. A synthetic CK (6-benzylaminopurine [6-BA]) and KCl with the concentration of 10 μM and 50 mM, respectively, were foliar sprayed on drought-stressed plants. The experiment consisted of well-watered control, drought stress followed by rewatering, drought stress followed by rewatering and foliar spray of 6-BA (10 μM), and drought stress followed by rewatering and foliar spray of KCl (50 mM). Treatments were arranged as a completely randomized block design with four replicates for each treatment. Soil volumetric water content (SWC), leaf relative water content (RWC), net photosynthetic rate (P_n), stomatal conductance (g_s), transpiration rate (Tr), and stomatal aperture decreased with the progression of drought stress. The RWC, P_n, g_s, Tr, and stomatal aperture increased after rewatering, to a greater extent in 6-BA- or KCl-treated plants than plants sprayed with water only. A positive correlation between stomatal aperture and P_n (r² = 0.79) and between stomatal aperture and g_s (r² = 0.87) were detected under drought stress and during rewatering. Our results indicate that exogenous application of 6-BA and KCl promoted stomatal reopening following drought-induced closure, leading to enhanced g_s and rapid postdrought resumption of photosynthesis on rewatering.

Potassium Fertilization in Rice-Wheat System across Northern India: Crop Performance and Soil Nutrients

Rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping in South Asia is under stress due to widespread removal of plant nutrients in excess of their application. We evaluated K, S, and Zn application to rice and wheat in 60 farmer’s fields in five districts across northern India. We compared the existing farmer’s fertilizer practice (FFP), which in most cases did not include application of K, S, or Zn, with application of K only, S + Zn, or K + S + Zn. Application of K increased rice yields by 0.6 to 1.2 Mg ha⁻¹ and wheat yields by 0.2 to 0.7 Mg ha⁻¹ across the locations varying in soil texture, soil K, climate, and irrigation. Application of S and Zn with K further increased yields. Added net return from fertilization with only K, as compared to FFP, ranged from U.S.$ 114 to 233 ha⁻¹ for rice and U.S.$ 29 to 214 ha⁻¹ for wheat. Added net return further increased when S and Zn were combined with K. Total plant K per unit of grain yield was comparable for mature rice and wheat (22 kg Mg grain⁻¹). Soil exchangeable and non-exchangeable K decreased without K application during one rice–wheat cropping cycle. Rice and wheat yields increased with application of K across the range in exchangeable soil K from 60 to 162 mg kg⁻¹. Approaches are needed to reliably predict fertilizer K requirements when crops respond relatively uniformly to K across a wide range in exchangeable K.

On the Social Situation of the Farming Population in Switzerland

As part of a social report, this paper traces the social situation of farmers in Switzerland in comparison with other occupational groups on the basis of the European Social Survey (ESS). With the social situation — which encompasses the quality of life and life opportunities of population groups — various factors such as job, income, unemployment, values, and integration in society are taken into account. The reference occupational group with which farmers are compared is critical for the interpretation of the results. In the assessment of their economic situation, the farming population differs little from other occupational groups; in terms of their subjectively perceived integration into society, the farming population does not fall behind other occupational groups. As far as values are concerned, depending on the reference, the farming population turns out to be less universalistic, less traditional, and more success-oriented.