Effect Of Potassium Fertilization Research Articles

Potato (Solanum tuberosum L.) Growth and Quality as Influenced by Inorganic Fertilizer Rates in Northwestern Ethiopia

Potato (Solanum tuberosum L.) is an important tuber crop that is highly affected by poor soil fertility and nutrient disparities. Nutrient depletion due to intensive monocropping and poor soil management practices is a serious problem in Ethiopia, including in northwestern areas. Therefore, an experiment was conducted in the East Gojjam zone of northwestern Ethiopia to evaluate the influence of phosphorus and potassium fertilizer rates on potato tuber production. Three phosphorus levels (0, 34.5, and 69 kg/ha−1) and four potassium levels (0, 100, 200, and 300 kg/ha−1) were set out in a factorial arrangement and replicated three times using a randomized complete block design. Data on growth and quality parameters, as well as plant tissue analysis results, were collected. According to the results, the main effects of phosphorus and potassium fertilizer rates statistically affected growth components. The combined effects of phosphorus and potassium fertilizers had a significant influence on quality components (tuber size distribution). Similarly, the interaction effects of phosphorus and potassium fertilizer rates gave the highest response in all nutrient use efficiency parameters. The combined application of 34.5 kg P2O5 and 200 kg K2O fertilizers resulted in the highest medium (28.32 ton/ha−1) and large-sized (20.0 ton/ha−1) tuber yields. The interaction effect of 34.5 kg P2O5 with 100 kg K2O ha−1 yielded the highest agronomic and recovery efficiency values. Hence, a combination of 34.5 kg P2O5 ha−1 and 200 kg K2O ha−1 fertilizer rates can be recommended for the optimal production of potato in the northwestern area.

Synergistic Effect of Azotobacter nigricans and Nitrogen Phosphorus Potassium Fertilizer on Agronomic and Yieldtraits of Maize (Zea mays L.).

Plant growth-promoting bacteria (PGPB) Azotobacter spp. is the most promising bacteria among all microorganisms. It is an aerobic, free-living, and N2-fixing bacterium that commonly lives in soil, water, and sediments. It can be used as a biofertilizer for plant growth and nutrient utilization efficiency. Maize is the highly consumed cereal food crop of the cosmopolitan population, and the sustainable maize productivity achieved by applying bacteria in combination with nitrogen phosphorus potassium (NPK) is promising. In the present study, a bacterial isolate (PR19). Azotobacter nigricans, obtained from the soil of an organic farm was evaluated for its plant growth promoting potential alone and in combination with an inorganic fertilizer (NPK) included. The bacterial cultue (PR19) was screened for its morphological, biochemical, and plant growth-promoting characteristics, sequenced by the 16S rDNA method, and submitted to NCBI for the confirmation of strain identification. Further, the inoculation effect of the bacterial culture (PR19) in combination with NPK on growth and yield parameters of maize under pot were analyzed. Based on phenotypic and molecular characteristics, PR19 was identified as Azotobacter nigricans it was submitted to NCBI genbank under the accession No. KP966496. The bacterial isolate possessed multiple plant growth-promoting (MPGP) traits such as the production of ammonia, siderophore, indole-3-acetic acid (IAA), and ACC Deaminase (ACCD). It showed phosphate solubilization activity and tolerance to 20% salt, wide range of pH 5–9, higher levels of trace elements and heavy metals, and resistance to multiple antibiotics. PR19 expressed significantly increased (p < 0.001) antioxidant enzyme activities (SOD, CAT, and GSH) under the abiotic stress of salinity and pH. In vitro condition, inoculation of maize with the PR19 showed a significant increase in seed germination and enhancement in elongation of root and shoot compared to untreated control. The combined application of the PR19 and NPK treatments showed similar significant results in all growth and yield parameters of maize variety SHIATS-M S2. This study is the first report on the beneficial effects of organic farm isolated PR19-NPK treatment combinations on sustainable maize productivity.

Effect of nitrogen and potassium fertilizers on melon plant productivity

The objective of this investigation was to evaluate the effect of different doses of nitrogen and potassium fertilizers on some production parameters of melon plants. The experiment was carried out in San Roque, which is 24 km from the city of Concepción, Paraguay, at the coordinates 57°14´10.29´´ South and 23°19´12.05´´ West. The study design was the completely randomized block with three replications in a split plot scheme 4 x 4. The dose used in the main plot was of N (0, 50, 100 and 150 kg ha-1) and in the sub-plot, K (0, 95, 190 and 285 kg ha-1). A light harrow was carried out to prepare the soil, seedlings were produced in 1500 cm3 pots of 60-micron thickness and the transplant was carried out when the seedlings had between 4 and 6 true leaves at 30 days after planting. Urea with 45% N was used as the source of nitrogen and potassium chloride 60% was used as the source of potassium. Fertilisation was carried out in September 2017 on two occasions: at 15 and 30 days after transplanting. The spacing used was of 1.5 m between rows and 1.5 m between plants, giving a total of 4356 plants ha-1. Harvesting began 90 days after planting and was carried out three times as the fruits reached commercial ripeness. The variables that were measured were average fruit weight (AFW), total soluble solids (TSS), polar diameter (PD), equatorial diameter (ED), fruit weight per plant (FWP). The data of the evaluated variables were subjected to the analysis of variance using the Fisher test where significant differences were found in: AFW, TSS, PD, ED and FWP. Subsequently, the regression analysis was performed (AFW, TSS and PD) and response surface (ED and FWP). The dose combination that produced the best values for equatorial diameter and fruit weight per plant was 71.9495 kg ha-1 of N and 160.554 kg ha-1 of K, 77.5921 kg ha-1 of N and 147.369 kg ha-1 of K, respectively. Key words: Cucumis melo L., fertilizer application, nitrogen, potassium, dose, weight, diameter, productivity

Straw residue incorporation and potassium fertilization enhances soil aggregate stability by altering soil content of iron oxide and organic carbon in a rice–rape cropping system

AbstractBoth iron (Fe) oxide and soil organic carbon (SOC) content, among other factors, drive the development and subsequent stability of soil aggregates. However, the mechanism of these drivers in paddy‐upland rotation systems with straw residue incorporation is not well understood. In this multiyear (2011–2017) trial, we sought to study the factors which drive the stability of soil aggregates in such a rice‐rape (RR) agronomic system. In order to examine the effect of straw residue incorporation and potassium fertilization on soil aggregation dynamics, we divided our trial into four treatments: inorganic phosphorus (P) and nitrogen (N) fertilizer; inorganic NPK fertilizer; inorganic NP fertilizer plus straw residue; and inorganic NPK fertilizer plus straw residue. Treatments which incorporated straw residue significantly increased both the geometric mean diameter (GMD) and the mean weight diameter (MWD) of soil aggregates. Soil aggregate stability was greater after rape harvest than after rice harvest, while SOC shows the opposite trend. Straw residue incorporation increased the SOC and, specifically, concentrations of aliphatic‐C and aromatic‐C, particularly in aggregates greater than 0.25 mm. Straw residue addition significantly increased both the amorphous (Feo) and complex iron oxide (Fep) contents of soil. In both bulk soil and in aggregates greater than 5 mm, SOC and Fep were positively correlated with MWD, while in aggregates less than 5 mm, Feo was positively correlated with MWD. Overall, we suggest that the increased concentrations of SOC, alkane‐C, Feo, and Fep in soils after incorporation of straw residue were responsible for increasing soil aggregate stability.

Effect of potassium fertilizer and alternate wetting and drying (AWD) irrigation system for Boro rice cultivation in Faridpur region

Effect of potassium fertilizer and alternate wetting and drying (AWD) irrigation system for Boro rice cultivation in Faridpur region

Effect of potassium fertilization in sandy soil on the content of essential nutrients in soybean leaves

Among the plant nutrients, potassium (K) plays a fundamental role in plant physiology and the soil-plant dynamics of various nutrients. Careful rate recommendations for K are needed to ensure that the balance between cationic nutrients and micronutrients is maintained, especially in sandy soils. The current research aimed to evaluate the absorption dynamic of several nutrients by soybean (Glycine max. Merrill.) growing in sandy soil under the application of five rates of K (0, 25, 50, 75, and 100 kg ha−1) via potassium chloride (KCl) with five replications. The concentrations of K+ in the diagnostic leaves of the soybean plants presented quadratic behavior with the increase in K rate and reached a maximum of 17.74 mg kg−1 at a rate of approximately 81 kg ha−1 K, which was found through a regression test. The leaf concentrations of calcium (Ca2+) and magnesium (Mg2+) decreased linearly with increasing K rate. By contrast, the leaf concentrations of the micronutrients; boron (B) and iron (Fe2+) decreased with increasing K rate. Soybean productivity was not influenced by the application of K. Principal component analysis (PCA) showed a clear influence of increasing K rates on the leaf nutritional parameters of soybean plants. The results confirm that the high application of K in sandy soils can disrupt the balance of nutrient uptake by soybean plants.

Effect of phosphorus and potassium fertilization on drought tolerance of broad bean (Vicia faba L.)

Effect of phosphorus and potassium fertilization on drought tolerance of broad bean (Vicia faba L.)

Effect of nitrogen, phosphorus and potassium fertilizers on growth and quality of sugarcane

Effect of nitrogen, phosphorus and potassium fertilizers on growth and quality of sugarcane

Effect of Water Stress and Potassium Fertilizer on Growth and Yield of Transplanted Aman Rice

Drought stress affects plant growth and development and ultimately reduces the grain yield of rice. The use of periodical water stress and potassium fertilization may enhance rice tolerance to drought stress. But drought at different growth stages may respond differently which is still unclear. This research work was carried out to determine the effects of different periodical water stress combined with potassium fertilization on growth, yield, leaf gas exchanges and biochemical changes in transplanted Aman rice (cv. BRRI dhan71) grown in the field condition and compare them with standard practice (control). Three levels of water stress (Control: Regular irrigation with 1 cm standing water, periodical water stress for 10 days from 15 days after transplanting (DAT) to harvest and water stress for 10 days after panicle initiation or reproductive phase) and two potassium (K) fertilization levels (41 kg K ha-1 and 51 kg K ha-1) were evaluated in this experiment. The application of water stress for 10 days at the reproductive phase and application of potassium at 51 kg K ha-1 showed tolerance to drought stress by increasing chlorophyll content, proline levels and maximum efficiency of photosynthesis in comparison to other treatments. It was observed that rice yield and other physiological parameters reduced with increasing duration of water stress by periodical water stress for 10 days from 15 DAT to maturity while application of additional potassium fertilizer (51 kg K ha-1) has a slight effect on those parameters. From our observation, 10 days of water stress at the reproductive phase of rice with potassium fertilization at 51 kg K ha−1 produced higher grain yield and yield components that are equivalent to standard practice. It was also observed that the biomass and filled spikelet were not affected by without irrigation for 10 days at reproductive phase. Therefore, it could be stated that the rice variety BRRI dhan71 does not require flood irrigation and water stress for 10 days at the reproductive phase is more appropriate to increase water use and optimum yield of rice. South Asian J. Agric., 8(1&amp;2): 36-44

Effect of potassium fertilizer application in teff yield and nutrient uptake on Vertisols in the central highlands of Ethiopia

AbstractTeff is the most dominant staple cereals in Ethiopia, but yield levels are extremely low (1.2 t/ha) because of declining soil fertility, resulting in widespread national food insecurity. The aim of this study was to explore the effect of potassium (K) fertilization on teff yield and nutrient uptake in Vertisols in the central highlands of Ethiopia. Five levels of K (0, 30, 60, 90, and 120 K2O kg/ha) were applied as muirate of potash (KCl) arranged in RCBD with three farm fields as replicates. At crop maturity, a plot of 3 m × 3 m was harvested to measure teff yield and yield components and subsampled for laboratory analysis to determine nutrient uptake. Results showed a highly significant (p&lt; 0.01) response of teff to K fertilizer application and significant differences among locations. When averaged across locations, the highest mean grain (1,875 kg/ha) and straw yields (6,774 kg/ha) were obtained with the application of 90 and 120 kg K2O/ha, respectively. However, the lowest grain (1,576 kg/ha) and straw (5,798 kg/ha) yields were harvested from control plots. This is about a 20% increase over the control. When averaged for all treatments, the highest mean grain (2,641 kg/ha) and straw (7,794 kg/ha) yields were obtained at Moretina Jiru and the lowest grain (1,280 kg/ha) and straw (4,210 kg/ha) yields were obtained at Sululta. Contrary to the popular view that Ethiopian Vertisols are rich in K, there are sites in the central highlands where K deficiency is limiting teff production. In sites where K-soil level was low and rainfall distribution was adequate, the application of K fertilizer along with the government recommended zinc blend fertilizer – NPSZn: 17.7 N + 35.3 P2O5+ 6.5 S + 2.5 Zn – significantly improves nutrient uptake, agronomic efficiency, and teff yields.

Effect of potassium fertilization on roselle yield and yield components as well as IWUE under deficit irrigation regimes

This research aimed to investigate different levels of irrigation water and potassium fertilizer on the yield and yield components as well as qualitative properties and irrigation water use efficiency (IWUE) of Roselle (Hibiscus sabdariffa). For this purpose, in 2019 and 2020, a factorial experiment with a randomized complete block design (RCBD) with three replicates was conducted in a semi-dry region. The experimental treatments included three levels of potassium fertilizer 75 t ha−1 (K1), 112.5 t ha-1 (K2), and 150 t ha−1 (K3) (equivalent to 50, 75, and 100% of potassium fertilizer percentage) and four levels of irrigation water including I1 (40%), I2 (60%), I3 (80%), and I4 (100%) of the plant water requirement. At the end of the experiment, quantitative parameters including plant height, weight and number of capsules, dry yield, and IWUE were measured. Further, qualitative parameters such as level of anthocyanin, protein, carbohydrate, proline, chlorophyll a and b were also measured to investigate the effects of water stress and fertilizer stress on the quality of Roselle. Experimental results revealed that the simple effects of irrigation water and potassium fertilizer became significant at 1 and 5% probability levels on all of the measured parameters. The greatest dry yield (600.95 kg ha−1) was obtained from l3K3 treatment. The maximum IWUE was achieved in l2K3 treatment (0.058 kg m−3). However, no significant difference was observed in this regard between l2 and l3. Qualitatively, with the reduction of the depths of irrigation water up to 60% the plant water requirement and with decline in the potassium fertilizer consumption, the level of anthocyanin, protein, carbohydrate, and proline increased by 85.16%, 19.56%, 15.34%, and 28.35% respectively. However, the values of chlorophyll a and b dropped by 42.75 and 24.54% respectively. On the other hand, no significant difference was observed between K1 and K2 in this regard. Thus, considering the water status of the region and deficit of water resources, application of 80% water requirement (treatment l3) would save water consumption, and consuming 75% potassium content (K2 treatment) would enhance the quality and modify the damages resulting from drought stress in Roselle.

Effect of different soil water tensions and potassium fertilization on the production and quality of netted melon (cucumis melo l.) in the Amazon area

The objective of this study was to evaluate the production and qualitative behavior of netted melon in a protected environment subjected to different soil water tensions and potassium doses, applied via fertigation. The experimental design was randomized blocks (RBD) in a 4 x 5 factorial scheme with 20 treatments and three replicates, consisting of five percentage doses of potassium (0, 50, 100, 150 and 200%) and four soil water tensions (15, 30, 45 and 60 kPa). The variables analyzed were average yield (t ha-1), transverse and longitudinal diameter of fruits (mm), pulp thickness (mm), °Brix (%) and pH. Yield and fruit longitudinal diameter were decreased linearly with the increase in soil water tension. The best result for yield and fruit longitudinal diameter of 51.24 t ha-1 and 127.7 mm were achieved, respectively, when irrigation performed at 15 kPa tension. The lowest value was found at the maximum tension (60 kPa). Regarding potassium doses, a quadratic model fitted to the data, with maximum values of yield and longitudinal diameter at the K2O doses of 235.30 and 232.82 kg ha-1, respectively. The interaction of T x K led to higher values of °Brix under 247.68 and 371.52 kg ha-1 of K2O with tension of 24.67 kPa, with no difference between both. The best result of fruit transverse diameter was observed under combination of 371.52 kg ha-1 of K2O and 15 kPa tension. Irrigation at tension of 15 kPa and K2O dose of 247.68 kg ha-1 can be indicated for the study conditions

Biomass Accumulation and Technical and Economic Efficiency of Potassium Sources Applied via Fertigation to Corn

To achieve high corn yield, optimal amounts of nutrients that can be extracted by the crop must be supplied at adequate proportions. Vinasse from sugarcane ethanol production can be applied as a soil fertilizer to corn crops in ethanol production plants. In this context, the present study compared the effects of mineral potassium fertilization with potassium chloride and organic fertilization with concentrated sugarcane vinasse on corn dry matter and grain yield and explored the technical and economic efficiency of these sources. The experiment was carried out at the experimental station of the Federal Institute Goiano, Rio Verde Campus, Brazil. The experiment followed a randomized block design in a 2 × 4 factorial scheme, with three replicates. The treatments comprised two sources of potassium, namely concentrated vinasse and potassium chloride, applied at four doses of potassium, representing 0%, 50%, 100%, and 200% of the recommended rate for corn. The dry matter accumulation of corn throughout the crop cycle, yield components at harvest, and technical and economic efficiency of the applied potassium sources were measured. Neither potassium dose nor its source affected leaf, stem, and aboveground dry matter accumulation at harvest. Regardless of the potassium source, the 100% dose produced higher cob dry mass, grain dry mass, grain dry mass per ear, grain yield, number of bags of 60 kg ha−1 produced per hectare, and harvest index. The agronomic efficiency of vinasse compared to potassium chloride was 68.5% at the 100% dose of the recommendation, showing enough potential as an organic fertilizer in corn crop.

Effect of potassium fertilization on water productivity, irrigation water use efficiency, and grain quality under direct seeded rice-wheat cropping system

A two-year field investigation was conducted to find out the right time, method, rate and source of potassium (K) fertilization for maximizing nutrient and water use efficiency and quality in a basmati rice-wheat cropping system. The split application of a recommended dose of K (RDK = 60 kg K2O ha−1) as half basal (B) and remaining half at panicle/ear initiation (PI/EI) stages significantly increased the system water productivity (SWP) (0.60 kg ha−1mm−1) and system irrigation water use efficiency (SIWUE) (1.26 kg ha−1mm−1) by 9.1% and 7.1% respectively over basal application of entire RDK. Likewise, in basmati rice, the split application of 100% RDK increased the water productivity (WP) and irrigation water use efficiency (IWUE) by 10.9% and 10.6% respectively over basal dressing of 100% RDK. The split application of RDK and supplementation of K through foliar spray besides basal K application increased the nitrogen, phosphorus and potassium concentration in grain and straw of both the crops. With respect to grain quality, the split application of 100% RDK increased the protein content by 2.3% in basmati rice, and 2.8% in wheat over basal application of 100% RDK. Similarly, the split application of RDK increased the hulling, milling and head rice recovery percentage of basmati rice by 1.3%, 6.6% and 3.3% respectively over basal application of RDK. The root length and dry weight of wheat was increased by 6.9% and 21% by split application of RDK over basal dressing of same dose of K.

Integrated Physiological and Metabolomic Analyses of the Effect of Potassium Fertilizer on Citrus Fruit Splitting.

Potassium (K) nutrition plays a key role in alleviating a variety of peel disorders in tree fruit, but the effect of this nutrient on the physiological and metabolic profiles involved in the fruit splitting of citrus remains unclear. Three levels of K were used to treat citrus ‘Ehime Kashi 34’ (Citrus Nishinoka × C. Shiranui), a hybrid cultivar with fruit that easily split. The results showed that the roots of the treatment with K fertilizer increased the contents of calcium (Ca2+), nitrogen (N), and K in the skin and flesh, the fruit firmness ratio of the peel to the flesh, photosynthetic rate, stomatal conductance, and concentration of intercellular CO2. In contrast, it decreases the relative chlorophyll index and content of Ca2+ in the leaves. Simultaneously, 59 and 13 differentially expressed metabolites (DEMs) were detected in the peel and flesh, respectively, after treatment with K. Of them, five compounds were upregulated, including the synthesis of various amino acids in the peel and the accumulation of various glycoside metabolites in the flesh which were upregulated. The accumulation of levels of gibberellin and glycoside were downregulated. That could be the main reason why potassium alleviates fruit splitting.

Effects of potassium fertilizer and straw on maize yield, potassium utilization efficiency and soil potassium balance

ABSTRACT A three-year field experiment was conducted to evaluate the effects of straw combined with potassium fertilizer on maize yield, potassium utilization efficiency and soil potassium balance. The study consisted of two straw treatments (S1: straw returning; S0: no straw returning) and five K levels (0,30,60,90,120 kg K ha−1). The results showed that compared to S0, the maize yield and available K content in S1 increased by 2.9%~6.2% and 19.3%~37.4%. The average of agronomy efficiency and surplus rate in S1 were 7.3%~35.4% and 24.8%~84.7% higher than S0 respectively, but the recovery efficiency, partial factor productivity under S0 and S1 were statistically identical. When the surplus rate is 0, the amount of potassium fertilizer required and the corresponding yield to maintain the soil K balance in S1 were 87.9 kg ha−1 and 12,424.6 kg ha−1. Compared to S0, S1 can decrease potassium fertilizer application rate by 10.2% while increasing maize yield by 3.5%. Overall, straw return combined with potassium fertilizer can improve maize yield and soil available potassium content, it can also reduce chemical fertilizer input while increasing fertilizer utilization efficiency, and play a positive role in keeping soil K balance simultaneously.

Potassium and phosphorus as limiting factors for erucic acid in the inedible oilseed crop, Crambe

Crambe (Crambe abyssinica Hochist.) is an oilseed crop with high in euricic acid with industrial uses in production of biodiesel, nylon, plasticizers, and lubricants. Little information is available about Crambe response to phosphorus and potassium fertilization. The aim of this study was to determine the effect of phosphate (25 and 50 P2O5 kg Fed.−1) and potassium (10 and 20 K2O kg Fed.−1) fertilization on the growth characteristics and oil quality of Crambe plants. The experiment had a randomized complete block design, and it was carried out in the Experimental Station of National Research Center, Cairo, Egypt in 2019 and 2020. The results showed that the application of potassium and/or phosphorus fertilization resulted in significant increases of all vegetative growth traits, such as plant height, number of branches, fresh weight, and dry weight as well as fixed oil content. The GC analysis of fatty acid identified eight compounds in the following order of main averages; erucic acid (50.5%), elaidic acid (23.1%), Linoleic acid (10.9%), linolenic acid (6.5%), palmitic acid (4.8%), eicosanoic acid (1.9%), stearic acid (1.3%), and oleic acid (1.0%). Phosphorus and potassium had opposite effect on the main components of Crambe oil. Erucic acid increased with potassium fertilization and decreased with phosphorus fertilization. Contrast results were shown in Elaidic acid in response to potassium and phosphorus fertilizations. These results suggested the positive effect of both potassium and phosphorus fertilization on growth and oil yield of Crambe plants as well as they considered as limited factors for Erucic acid content.

Optimizing Planting Density and the Use of Potassium Fertilizers for the Prospect of Enhancing Yield of Field Grown ‘CXD_222’ Tomatoes

Background: Potassium fertilizer and optimum planting density are important factors for maximizing fruit yield in field grown tomatoes. We conducted a field study to evaluate the effects of planting density and potassium fertilizers on the yield performance of CXD_222 tomatoes. Materials and Methods: We evaluating the fruit yield of CXD_222 tomatoes in NP + 50 (nitrogen and phosphorus in a 50 x 50 cm planting pattern), NP + 40 (nitrogen and phosphorus in a 40 x 40 cm planting pattern), NPK + 50 (nitrogen, phosphorus, and potassium in a 50 x 50 cm planting pattern), and NPK + 40 (nitrogen, phosphorus, and potassium in a 40 x 40 cm planting pattern). Findings: Wider spacing (NPK +50 and NP + 50) resulted in significantly heavier fruits per plants and produced more fruits per plants. Narrow spacing; however, produced significantly higher yield per square meter. The effect of potassium fertilizer was obvious in a sense that planting space treatments with potassium fertilizers produced significantly higher yield than the corresponding treatments without the application of potassium fertilizer. The highest yields of 5.2 and 4.75 kg m-2 were achieved in NPK + 40, NPK+50 and NP + 40, respectively whereas bigger and more fruits per plants were harvest from NPK + 50 and NP + 50, respectively. Conclusion: This study indicates that optimizing planting space and the use of potassium fertilizers will significantly enhance fruit yield.

Effects of fertilization on the growth dominance of Inland Northwest forests of the United States

Large trees have disproportionally large competitive advantage in access to light, which has been proposed to increase growth dominance of large trees (e.g., a larger proportion of volume growth than standing volume is in large trees in a stand). Tree growth may also be limited by the availability of other resources besides light. Nutrient deficiency, especially of nitrogen, is considered common among temperate forests including mixed-conifer forests of the Inland Northwest of the United States. Data from a long-term forest nutrition study across four Inland Northwest states were analyzed to evaluate nitrogen ​× ​potassium fertilization's effects on growth dominance over an eight-year period following treatment. Our results show that growth dominance varied substantially across plots in each vegetation series and fertilization treatment, and its mean values generally were at minuscule magnitudes, negative, and not significantly different from 0. We propose that this lack of a clear pattern in growth dominance was the result of the mixed-species composition where shade-tolerant species remained in lower crown positions, yet their relative growth kept pace with large trees. Limited moisture availability at dry sites may have hampered the development of growth dominance. Growth dominance also was lowered by mortality observed among relatively large trees. The largely negative growth dominance across fertilization treatments indicated that small trees seem to have maintained higher relative growth rates than large trees, even if absolute growth was higher among large trees. In the case fertilization does improve stand growth, a significant part of this improved growth will be lost in density-dependent mortality over time if not captured through thinning/harvesting.

Rootstock and potassium fertilization, in terms of phenology, thermal demand and chemical evolution, of berries on Niagara Rosada grapevine under subtropical conditions

This study aimed to assess the effect of rootstocks (IAC 572 and IAC 766) and potassium fertilization at different concentrations (0, 75, 150 and 300 kg·ha-1 K2O) on the phenology and thermal demand of the Niagara Rosada grapevine, and to evaluate the development of chemical traits during maturation stage. The length of the main phenological stages was recorded within two production seasons. Total thermal demand was calculated using the degree-day concept. The berries’ titratable acidity and soluble solids contents were determined during maturation. Results indicated that IAC 572 and IAC 766 rootstocks along with potassium fertilization had no influence on the phenological cycle or thermal demand of the Niagara Rosada grapevine. The production cycle lasted 144 to 148 days with thermal demands ranging from 1,465.2 to 1,615.1 degree-days. For better grape quality, i.e., with a balance between soluble solids and acidity levels, it is estimated that the grape harvest is carried out around 21 to 24 days after the veraison.