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To assess the effects of ozone (O3) on uptake and utilization of nitrogen, phosphorus, and potassium nutrients in rice for planning rational fertilization under projected O3elevation. Two hybrid indica cultivars were exposed to ambient and elevated O3(E-O3) under a free-air O3enrichment system. E-O3differently affected the accumulation and distribution of biomass, and the absorption and distribution of nutrients between cultivars. These effects were related to rice cultivar and nutrient type. E-O3led to significantly decreased partial factor productivity and grain production efficiency (GPE) of nitrogen in both cultivars; however, the effects of E-O3on GPEs of phosphorus and potassium varied with cultivar. Responses of nutrients harvest indices between cultivars to E-O3were adverse. Differences between cultivars and elements should be considered when examining E-O3potentially affecting the nutrient dynamics for the purpose of reducing the amount of fertilizer applied in paddy systems to decrease potential environmental pollution. [ABSTRACT FROM PUBLISHER]

Nutritional status of vegetable crops is often monitored by analysis of dried plant tissues, which is costly and often time consuming. Two greenhouse trials were conducted, at the University of Hawaii at Manoa, Magoon facilities, to evaluate the portable cardy ion meter (CIM) in determining potassium (K+) status in fresh petiole sap of pak choi as compared with standard laboratory methods. In the first greenhouse trial, three algae species (Gracilaria salicornia, Kappaphycus alvarezii, and Eucheuma denticulatum) were used to apply five rates of K+(0, 84, 168,252, and 336 kg.ha−1). The pak choi was directly seeded into 4 L pots and was grown in peat moss. In the second greenhouse trial, K+ was provided through Eucheuma denticulatum and potassium nitrate (KNO3) at five rates (0,112, 168, 224, 280, and 336 kg.ha−1) in peat moss and soil media. At harvest, K+concentrations in fresh petiole sap were analyzed immediately with CIM and the dried samples were analyzed by inductively coupled plasma spectroscopy (ICP) measurement. The results showed increase in leaf K+ content at higher rates and the maximum concentration of leaf K+at 4500–5300 mg/L for sap and 8–9% for tissue was obtained when K+was provided between 224 and 284 kg.ha−1. There was a close correlation between the CIM readings and the ICP method (r = 0.8048 and 0.8314) from the first and second GH results, respectively. The results suggest that the CIM could be used for the rapid monitoring of the relative K+status of plants. The data further suggested 4500–5000 mg K/L for fresh petiole sap and 7.5% K+in tissue as critical levels for K+concentration in pak choi. [ABSTRACT FROM AUTHOR]

In the present study, the effects of inoculation of biofertilizers (phosphorus-solubilizing arbuscular mycorrhizal (AM) fungi (AMF),Glomus intraradices, and potassium-mobilizing bacterium (KMB),Frateuria aurantia) in combination with chemical fertilizers nitrogen, phosphorus, and potassium (NPK) on growth, yield, nutrient acquisition, and quality of tobacco were observed in pot culture. Factorial combinations of biofertilizers (AMF and KMB) and chemical fertilizer (NPK) alone and in combination were applied to see the effects on growth, biomass, nutrient acquisition, and leaf quality in tobacco. Results showed that bioinocula applied either singly or in combination did not significantly enhance soil availability of P and K, indicating their unsuitability for direct application. Application of chemical fertilizer in combination with both AMF and KMB strains consistently increased availability of P and K in the soil, improved leaf quality parameters, and enhanced plant growth and vigor, suggesting the potential use of AMF and KMB as biofertilizers in sustainable tobacco crop production. [ABSTRACT FROM AUTHOR]

The use of cultivar with nutrient-use efficiency is an important strategy in the management of plant nutritional status, particularly potassium (K), because its high demand and the progressive impoverishment caused by the use of inadequate amounts cause frequent deficiency symptoms observed in soybean [Glycine max(L.) Merrill] crops. This study was conducted in greenhouse conditions in a completely randomized design with four replicates in an Typic Quartzipsamment soil aimed to assess the effect of applying two rates of K (50 and 200 mg kg−1) on growth, shoot dry weight yield (SDWY) and seed yield (SY), nutritional status, yield components, and efficiency of K use in eleven cultivars of different characteristics and growth habits. The SDWY, SY, number of seeds per pod, number of pods, and estimated 100-seed weight showed significant interaction between cultivar and the K rates, with greater values at the rate 200 mg K kg−1. Similarly, the concentration of nitrogen (N), phosphorus (P), K, calcium (Ca), magnesium (Mg), sulfur (S), boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) in leaves and grains varied according to the K rates and in the cultivar. The most K-use efficient cultivars were BMX Magna RR, BRS 232, BRS 284, BRS 294RR, NA 5909RR, and Vmax RR, whereas FTS Campo Mourão RR was inefficient. Regarding response to fertilization, the cultivars Vmax RR, BMX Magna RR, NA 5909RR, BRS 284, and BRS 294RR were found to be efficient and responsive, whereas the cultivar FTS Campo Mourão RR, BRS 232, BMX Potência RR, BRS 295RR, TMG 1066RR, and TMG 1067RR are inefficient and responsive to K application in the soil. [ABSTRACT FROM AUTHOR]

This study focuses on two genotypes of cotton and explores different factors that were able to affect the release of different forms of potassium (K) in the rhizosphere by considering a biogeochemical process integrating plants, soils, and microorganisms. The study indicated that both genotypes of cotton could effectively absorb exchangeable potassium (eK) under limited potassium (LK) supply, and cotton plants could use LK to sustain offspring, preferably under K-deficiency conditions. It was mainly due to its significantly greater active absorbing surface area of root and comparatively greater K+maximum uptake rate (Imax), which caused more K accumulation in the high-efficiency genotype cotton (HEG). Although Imaxof the low-efficiency genotype cotton’s (LEG’s) was greater, K accumulation in LEG was less, which might be attributed to its significantly lower HEG and feedback inhibition on K taken up by greater K concentration in the plant. The lint yield had a significant positive correlation with boll number per plant, single boll weight, plant height, and number of fruit branches, which indicated that increasing these agronomic parameters is the base for increasing lint yield. There was a synergic action among humus, microorganisms, and K in the rhizosphere soil. The cation exchange capacity (CEC) of reduced soils was less under oxidized condition, due to collapse of the interlayer in response to increased layer charge upon structural Fe reduction. Crop yields can be increased when fertilizer K is applied according to proper ratio among different forms of potassium and humic acid in soils. The middle-high plant height, lower initial fruit branch, more fruit branches, more bolls, and larger boll size should receive more attention during high-yielding cotton breeding. [ABSTRACT FROM AUTHOR]

Rice is a staple food for about 50 percent of the world’s population. Potassium (K) is absorbed in large amounts by rice plants and adequate amounts of this element are fundamental to improve productivity and maintain sustainability of the cropping systems. A greenhouse experiment was conducted to determine the adequate rate of K for lowland rice grown on a Brazilian Inceptisol. The K rates used were 0, 50, 100, 200, 400, and 600 mg K kg−1soil. Most of the growth, yield, and yield components were significantly and quadratically increased with increasing K levels. Based on a quadratic equation, maximum grain yield was obtained with the addition of 371 mg K kg−1soil. Maximum plant height and shoot dry weight were obtained at 414 and 398 mg K kg−1soil, respectively. Root growth (maximum length and dry weight) was also significantly increased in a quadratic fashion with the increasing K rate in the growth medium. Maximum root length was achieved at 58 mg K kg−1whereas maximum root dry weight was obtained with the addition of 394 mg K kg−1soil. Plant height, shoot dry weight, 1000-grain weight, root length, and root dry weight were significantly associated with grain yield. Hence, manipulation of these growth and yield components with the addition of K fertilizer can improve yield of lowland rice in varzea soils of central part of Brazil. Potassium uptake increased significantly in a quadratic fashion with increasing K rate. However, K-use efficiency (mg grain per mg K applied) decreased significantly with increasing K rate in a quadratic fashion. Maximum grain yield was obtained with 117 mg kg−1Mehlich 1–extractable K, base saturation of 53 percent, Mg saturation of 9 percent, K saturation of 2 percent, and Ca/Mg ratio of 4. [ABSTRACT FROM AUTHOR]

A field experiment with wheat (Triticum aestivumL.) was established over two growing seasons where farmyard manure and sewage sludge, along with conventional fertilizer, were added to soil. We found that ammonium N was at greater concentrations in the organic amendments treatments, indicating more beneficial dynamics (i.e., it can be taken up by plants for a greater amount of time) and thus a longer lasting effect as a nutrient for the test crop. We found that nitrogen (N), phosphorus (P), and potassium (K) uptake increased with added organic amendments. This means that when organic matter along with nutrients are added to soil, productivity may increase beyond preset targets because soil conditions greatly improve, not only chemically but also physically. Nitrates left over at the end of the growing season (residual N) were greater in the high sewage sludge and manure treatments, but not proportionally. [ABSTRACT FROM AUTHOR]

As a consequence of increasing water demand, lack of natural water resources, and use of high amounts of fertilizers in the greenhouse crops in arid and semi-arid areas, the use of reclaimed municipal wastewaters is a valuable option, although the knowledge of plant nutritional requirements becomes more important to avoid imbalances caused by the nutrients present in reclaimed wastewater and to attain efficient nutrient use. An experiment was conducted with greenhouse-grown sweet pepper (Capsicum annuumL. var. Aifos) on a sand-mulched sandy loam soil and fertigation with recycled municipal wastewater and inorganic fertilizer treatments. Five treatments were applied: control with no nitrogen (N) or potassium (K) supplied (N0K0) and four different doses of N and K as the mean elements with possible imbalances: N1K1, N1K1.5, N1.5K1, and N1.5K1.5. N1K1was the recommended rate under local conditions (125 kg N ha−1and 193 kg K ha−1). Eight plants per treatment were collected at five growth stages (0, 56, 84, 113, and 155 days after the seedling transplant, DAT). Dry matter (DM) and N, phosphorus (P), K, calcium (Ca), and magnesium (Mg) concentrations in fruit, leaf, stem, and pruning wastes were measured for each sampling date. For all treatments, the period of largest extraction of nutrient by plant occurred from 113 to 155 DAT, which coincides with the greatest accumulation of dry matter. Plant nutrient distribution showed that fruit is the largest sink of N, K, and P. The NK levels showed no effect on DM and nutrient uptake in the periods of vegetative growth, fruiting, and fruit growth. Nutrient uptakes by the plant were not affected by NK level applied. The NK rates could be lowered significantly without reducing DM and nutrient total uptake by plant during vegetative growth, flowering, and early fruit development periods, when using reclaimed municipal wastewater. The fertigation with greater rates of N and K for the harvest period can be considered as an adequate and sustainable procedure to grow greenhouse pepper. [ABSTRACT FROM AUTHOR]

The use of regenerated water (RW) for irrigation of horticultural crops in the Mediterranean area could contribute to reduce fertilizer inputs, water consumption, and contamination of the environment. The nutrient content of RW and nutrient demand by crops needs to be match to achieve these benefits. This work studies the influence of different levels of nitrogen (N)– potassium (K) fertigation with purified wastewater obtained from Almería city, Spain, on yield, fruit quality, and macronutrient uptake of pepper plants. The experiment was conducted in a polyethylene greenhouse with pepper cv. Aifos, grown on a sand-mulched sandy loam soil using trickle irrigation. The experimental design was randomized blocks with four replicates. Six treatments were applied: two unfertilized controls (RW and ground water, GW) and four NK levels with regenerated water, RW (N1K1, N1K1.5, N1.5K1, and N1.5K1.5). N1K1is the recommended rate under local conditions, and 125 kg N ha−1and 193 kg K ha−1respectively are average nutrient concentrations in fertigation of 9.8 mM N (NO3−+ NH4+) and 5.4 mM K. The results showed that production parameters were equal in unfertilized RW irrigated plants compared to those irrigated with GW water, both resulting in low commercial production. Fertigation with N1K1produced yields similar to the RW control. Significant increases in marketable yields, number, and weight of fruit were recorded with N1.5K1.5, N1K1.5, and N1.5K1rates compared to RW control. The NK level had no effect on fruit quality attributes (pH, fruit firmness, total soluble solids, and titratable acidity of fruit). Nutrient uptake of plants followed the same order in all treatments: K > N > calcium (Ca) > magnesium (Mg) > phosphorus (P). The treatment N1.5K1.5showed the greatest uptake of N and P, and K uptake was similar to N1K1.5and N1.5K1treatments. [ABSTRACT FROM AUTHOR]

Nowadays, there is increasing interest in environmentally friendly growing systems, and attention has also been paid to the environmental impacts of natural and artificial fertilizations. However, seasonal dynamics of macronutrient status needs further investigations in environmentally friendly apple orchards. Therefore, this study was aimed to determine nitrogen, phosphorus, and potassium contents of leaves in every month during the season and of soil in April and October at Debrecen-Pallag, Hungary, from 2002 to 2004. The study was performed in integrated and organic apple orchards on three apple cultivars (Mutsu, Elstar, and Reka). All easily soluble (0.01 M CaCl2) and plant-available nitrogen fractions (nitrate nitrogen, ammonium nitrogen, and total soluble nitrogen) in the soil were significantly higher (P = 0.05) in the integrated apple orchard compared to the organic one. The 0.01 M calcium chloride (CaCl2) soluble ortho-phosphate and total phosphate fractions of the soil were significantly higher (P = 0.05), whereas organic phosphate and soil pH showed no significant difference in the integrated apple orchard compared to the organic one. Potassium contents of the integrated soils were significantly higher (P = 0.05) compared to those of the organic one. Nitrogen, phosphorus, and potassium contents of leaves were higher in the integrated orchard compared to the organic one. The dynamics of P uptake corresponded to the phenological phases of apple. Potassium content of apple leaves decreased continuously until July, after that it slightly increased, and then it decreased again. In conclusion, results suggest that better mobility of artificial fertilizers in integrated orchards provided higher macronutrient uptake than in organic orchards, where only natural nutrient sources are allowed. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the optimum time for plant analysis, which can provide useful indications of nutrient deficiencies in plants, and to establish limit values for nutrient supplies to fiber hemp (Cannabis sativa L.). The effect of nutrient supplies on the nutritional status of fiber hemp was estimated by leaf analysis in a long-term field fertilization experiment at four nitrogen-phosphorus-potassium (NPK) levels on Chernozem meadow soil in Szarvas, Hungary, in 1999 (good water supplies) and 2003 (dry). The optimum time for the diagnostic analysis of fiber hemp was found to be late May or early June, when plants in the five- to -seven-leaf stage are 70-100 cm in height, with a biomass of 2-5 t ha-1 dry matter, depending on water and nutrient supplies, variety, and production condition. Nutrient supplies to hemp can be considered satisfactory if plant analysis reveals 5-6% N, 0.5-0.6% P, and 2.7-3.0% K in the youngest fully developed leaves in late May. A stem yield (10% moisture content) of 12-17 t ha-1 was achieved when rainfall supplies were adequate (1999), whereas in the dry year (2003), the lower nutrient concentrations in the uppermost leaves, indicating nutrient deficiency, resulted in a maximum stem yield of only 6-8 t ha-1. The low, satisfactory, and high values for the concentrations of N, P, K, calcium, magnesium, iron, manganese, zinc, and copper reported in the article could be used to elaborate a fertilizer recommendation system for hemp. [ABSTRACT FROM AUTHOR]

Farmers in the lower corn belt region of the United States need to know how to fertilize soils in order to optimize the efficiency of potassium (K) use by plants under different tillage systems and with high yield management. A field study was conducted from 1994 to 1996 at the Dixon Springs Agricultural Center (DSAC) on a Bonnie silt loam (fine‐silty, mixed, mesic Typic Fluvaquent) soil and at the SIU Belleville Research Center (BRC) on a Herrick silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) soil. No‐till (NT) and spring chisel tillage (CT) systems were compared in a corn(Zea maysL.)‐soybean(Glycine maxL.) rotation. Within each tillage system, K rates of 56, 112 and 168 kg K ha‐1as potassium chloride were combined with four placement methods that included surface broadcast, 25‐cm surface band over the intended row, surface dribble 15 cm to the side of the intended row, and starter placement of 28 kg K ha‐15 cm to the side and 5 cm below the seed at planting (with the remainder of the K surface broadcast). The broadcast K placement most often produced the lowest whole plant K composition of corn or soybean tissue when sampled within a month after emergence. This indicated that the broadcast treatment was less efficient than other placement methods in providing K in the early stages of plant development. However, by the reproductive stage of development, there were no differences in leaf K concentrations among the various placement methods for either crop. Increasing K rates almost always increased leaf K concentrations and usually increased early plant growth and yields. Early plant growth and grain yield were affected to a greater degree in corn than soybean. Soybean yields appeared to maximize at 56 kg K ha‐1, whereas corn often showed higher yields (although not always significant) with K rates of 112 and 168 kg ha‐1. Corn usually requires more K than soybean, which would explain its greater responsiveness to K. For corn, the placement method of K was not as critical as rate, even for no‐till, across the six site‐years of this study. Lower yields occurred in 1996 at both locations with the long term banding of K fertilizers over the intended rows of soybean. This is in contrast to a yield benefit from surface banding at other locations or crops as reported in the literature. Weather problems related to a wet spring followed by dry conditions late in the season may have contributed to the atypical results in 1996. These weather problems probably either lead to larger plants early which ran out of water late in the season, or higher accumulated salt concentrations in the root volume which reduced water uptake late in the season. [ABSTRACT FROM PUBLISHER]