Kg Ha-1 Of K2O Research Articles

Produção de alface crespa utilizando água residuária da mandioca como fonte de potássio

ABSTRACT Cassava wastewater (CWW) is a natural biofertilizer successfully tested as a source of K in long-cycle crops; however, it still needs to be better evaluated in short-cycle crops. This study aimed to evaluate the use of CWW as a source of K in the growth, yield, and physicochemical quality of curly lettuce. The study was conducted in a greenhouse, in a randomized block design arranged in a 5 × 2 + 1 factorial scheme, with four replicates. Five CWW doses were evaluated as an exclusive source of K: 0, 60, 120, 180, and 240 kg ha-1 of K2O; two forms of application: 1-total dose at planting: 2-application of 50% of the dose at planting + 50% of the dose in topdressing, and an additional treatment: 100% mineral fertilization at 120 kg ha-1 of K2O dose, using KCl as the source. The number of leaves (NL), plant height (PH), fresh mass (FM), dry mass (DM), moisture (MO), ashes (ASH), fibers (FB), lipids (LIP), proteins (PTN), and carbohydrates (CHO) contents were evaluated. All agronomic attributes of lettuce showed lower values when fertilized only with CWW than mineral fertilization. Lettuce fertilized only with CWW, depending on total or split application and dose, showed higher ASH, FB, LIP, PTN, and CHO contents reaching 4.05, 3.97, 1.75, 7.11, and 3.63%, respectively, compared to mineral fertilization. The CWW can potentially be used as a complementary K source in lettuce cultivation, as its exclusive use does not replace traditional mineral fertilization.

Enhanced potassium use by colored cotton cultivars in the semiarid region of Brazil

Proper potassium (K) fertilization management is crucial for optimizing yield and minimizing environmental impacts in colored fiber cotton cultivars, particularly in semiarid regions. This study aimed to assess the efficiency of K use by colored cotton cultivars under K fertilization in a semiarid region. Two experiments were conducted in 2019 and 2021, representing two agricultural seasons. The experimental design employed randomized blocks with split plots and four replications. The main plots consisted of five randomized K doses (0, 60, 120, 180, and 240 kg ha-1 of K2O), while subplots included four cultivars of colored cotton (BRS Rubi, BRS Safira, BRS Topázio, and BRS Verde). The results revealed that BRS Rubi exhibited superior agronomic efficiency with a dose of 60 kg ha-1 of K2O in both agricultural seasons. The maximum efficiency of K use by colored cotton cultivars was achieved with a dose of 240 kg ha-1 of K2O in the semiarid region of Brazil. The cultivars BRS Rubi and BRS Topázio demonstrated the highest use efficiency. Furthermore, BRS Topázio displayed the highest K accumulation in plant shoots during both seasons.

Early potassium fertilization in cover plant previous to soybean crop in highly weathered soil

Soybean crops are of great economic importance in Brazil due to its cultivation in different regions of the country, like in Mato Grosso with approximately 19,235.60 thousand hectares cultivated annually and a production of 86,484.30 thousand tons in the 21/22 harvest. Direct sowing has been widely used in production, the plants that precede the crop are fertilized, with increased benefits of the use of straw through nutrient cycling, and the succession crop would benefit from the potassium, being a way that guarantees greater fertilization efficiency, with potassium being released gradually into the soil. The objective was to evaluate the effect of potassium doses applied to U. ruziziensis on forage straw production and potassium availability in the soil profile cultivated with soybeans in succession. The experimental design was in randomized blocks, with five (5) treatments and four (4) replications, totaling twenty (20) plots. The size of each plot was 2 m wide by 3 m long (6 m²). The treatments consisted of (T0) control, (T1) 25 kg ha-1 of K2O, (T2) 50 kg ha-1 of K2O, (T3) 75 kg ha-1 of K2O, (T4) 100 kg ha-1 of K2O. Straw productivity was evaluated, potassium content was determined, and potassium accumulation by forage straw was calculated. The potassium doses provided a linear increase in straw production, potassium content and accumulation in U. ruziziensis., with the highest potassium content in the soil being obtained in the first 20 cm of soil.

Early fertilization during winter cultivation and its residual effect on silage maize grown sequentially

The objective of this study was to evaluate the effect of an early application of potassium (K) fertilizer on pearl millet (Pennisetum glaucum L.) grown during fall/winter on the performance of maize (Zea mays L.) silage grown in succession. Using a randomized block design, in the fall/winter harvest, the plots were composed of millet and six doses of K (0, 30, 60, 90, 120 and 150 kg K2O ha-1) as muriate of potash (57% K2O) in addition to fallow. In the summer harvest, during the cultivation of maize, six doses of K2O were applied complementary to the doses applied in the autumn/winter harvest to total 120 kg K2O ha-1 (120, 90, 60, 30, 0) and 0 kg K2O ha-1 for the no cover treatment. An additional treatment that was planted to received the recommended fertilization amount (60 and 90 kg ha-1 of K2O for planting and broadcasting, respectively). For the millet, was evaluated plant height, green and dry biomass yields, and soil cover at 30, 60, 90 and 120 days after harvest . For maize, agronomic traits, leaf nutrient content and green and dry biomass yields were evaluated. The early application of K fertilizer did not alter the yield components of millet and silage maize. However, the straw produced by the millet was efficient at promoting soil cover in the off-season.

Zucchini squash yield response to fertilization with different doses and sources of Potassium

Potassium (K) is essential nutrient to the physiological and biochemical activities of plants, acting in the cation-anion balance, water movement, osmoregulation, and transference of energy. This study aimed to evaluate the yield response of the zucchini squash cultivar 'Caserta' to different doses and sources of potassium. The experiment was carried out under field conditions in a complete randomized block experimental design in a 6 x 2 factorial scheme, with six K2O doses (0, 50, 100, 150, 200, and 250 kg ha-1) and two sources (chloride and potassium sulfate), with four replications. The fruit mass, fruit length, number of fruits per plant, total and marketable fruit yields were evaluated. The results showed that the sulfate and potassium chloride sources promoted the maximum length and number of fruits per plant. K2O fertilization in the form of potassium sulfate promoted higher mass and total fruit yield. The doses of 108.41 and 130.78 kg ha-1 of K2O in the chloride and potassium sulfate sources provided the maximum marketable yield of fruits, with 22.84 and 27.0 t ha-1, respectively. Regardless of the source, potassium fertilization must be provided to increase the production parameters of the zucchini squash 'Caserta' cultivar.

Optimum Application Rate of Nitrogen, Phosphorus, and Potassium Fertilizers for Kenaf (Hibiscus cannabinus L.) Yield and Soil Chemical Properties in a Reclaimed Paddy Soil: A Pot Experiment

Kenaf (Hibiscus cannabinus L.) has been considered one of the alternative crops for bioenergy production, potentially replacing fossil fuel. However, there are few studies available on systematically investigating kenaf growth characteristics and its fertilization conditions so far. Our study investigated its biomass productivity and soil properties at the different fertilization regimes including three major treatments (N, P2O5, and K2O) with four application levels [0%-50%-100% (as recommended), and 200%] in a reclaimed paddy soil during pot experiment under upland condition in 2021. The results showed the maximum of kenaf biomass productivity was observed when 158 kg ha-1 of N, 156 kg ha-1 of P2O5 and 102 kg ha-1 of K2O were applied, showing 62.6 g d.w pot-1, 64.1 g d.w pot-1, and 64.9 g d.w pot-1, respectively. Our study revealed that kenaf biomass mainly showed positive correlations with electrical conductivity (EC) and total N contents in soils, suggesting that these could be major growth limiting factors for kenaf production. Our study provides a better understanding for producing the maximum kenaf biomass, filling the gap on a promising nutrient management strategy for its optimum production in southern reclaimed paddy soils.The effect of kenaf biomass productivity at different inorganic fertilization regimes in a reclaimed paddy soil during the pot experiment.

EFFECT OF SHOOT PRUNING INTERVAL AND DOSAGE OF POTASSIUM FERTILIZER ON GROWTH AND YIELD OF YAM BEAN (PACHYRHIZUS EROSUS L.)

A study was conducted in Baratan village, district of Patrang, Jember, East Java, on the effects of shoot pruning intervals and potassium fertilizer dosages on the growth and yield of yam bean (Pachyrhizus erosus L.). Pruning of the plant shoot was done six weeks after planting, 50 cm above the soil surface. Three levels of shoot pruning treatment were: no pruning (control), shoot pruning every 7 days, and shoot pruning every 14 days. The dosages of potassium fertilizer were: 0, 75, 150, 225, and 300 kg ha1 of K2O. The experimental design adopted was the completely randomized block design (CRBD) with three replications. The results showed that pruning of shoots every 7 days with potassium fertilizer at 225 kg ha-1 gave the best effect on leaf area index, tuber diameter, tuber fresh weight, tuber dry weight, and total plant fresh weight and dry weight, respectively. Those values were 6.1; 18.88 cm; 468.56 g, 89.05 g, 710.32 g, and 143.54 g, respectively. There was an increase of 289, 175, 392, 362, 247, and 223 percent again without pruning and potassium fertilizer (control) treatments. Pruning shoots every 7 days with 300 kg ha-1 potassium fertilizer resulted in the highest tuber carbohydrate content, which was 44.99 percent higher than the control treatment (no pruning and potassium fertilizer application).

Nutritional efficiency in sunflower cultivars under dosages of potassium in semiarid region

Potassium (K) participates in critical processes in sunflower cultivation, such as osmotic regulation and translocation of photosynthesis. However, the absorption or accumulation of this nutrient occurs differently owing to edaphoclimatic factors or between cultivars. The objective of this study was to evaluate the nutritional efficiency of sunflower cultivars as a function of different dosage K dosages in a semiarid region. To this end, two experiments were conducted in 2016 and 2017. The treatments consisted of five dosages of K at 0, 30, 60, 90, and 120 kg ha-1 K2O and four sunflower cultivars, Aguará 6, Altis 99, Multissol, and BRS 122. The experimental design was a randomized block with four replications and subdivided plots. The characteristics evaluated were agronomic efficiency, physiological efficiency, recovery efficiency, utilization efficiency, and accumulation of total K in the plant. Sunflower cultivars responded to K dosages in the two crops, with variations in efficiency parameters. Crop 2 showed better nutritional efficiency compared to crop 1. Aguará 6 showed greater nutritional efficiency than the other two crops. The use of dosages between 75 and 91 kg ha-1 of K2O provided better efficiency in K usage for the cultivars.

Characteristics of watermelon fruits under different fertilization management in semi-arid climate conditions / Características de frutos de melancia sob diferentes manejos de adubação em condições de clima semiárido

This study was conducted to evaluate the production and quality of watermelon fruits, submitted to different doses of potassium chloride (KCl) in fertigation and conventional fertilization systems. Talisman F1 was used as a plant material. It was carried out in a randomized complete block design, in a 2x4 split-plot scheme, with four replications. In the plots, the conventional and fertigation systems were tested and in the subplots the doses of KCl, equals: 0, 60, 120 and 180 kg ha-1 of K2O were tested. Seventy days after planting, were determined: total number of fruits; average weight of total fruits; total fruit production; average number of commercial fruits; average weight of commercial fruits and commercial fruit production, as well the hydrogenic potential (pH), total soluble solids (TSS), total titratable acidity (TTA) and TSS/TTA ratio. There was interaction between fertilization systems and K2O rates for commercial productivity with a linear increase under fertigation, which, in turn, increased TTA. 180 kg ha-1 of K2O in a conventional fertilization system, confirm possible metabolic changes not conducive to the cultivation and production of 'Talisman F1' watermelon. The fertilization system by fertigation represents an alternative for the cultivation of watermelon, considering the productivity and quality of fruits.

YIELD TRAITS OF SOYBEAN CULTIVATED UNDER BRACHIARIA AND MILLET STRAW AND POTASSIUM DOSES

There are many doubts about which straw-supplying species should be cultivated in a no-tillage system and which potassium doses are adequate for the Cerrado soils. Therefore, the current study aimed to evaluate the agronomic traits (plant height, first pod insertion height, and stem diameter); yield traits (number of pods per plant, number of grains per pod, and 100-grain weight), grain yield (kg ha-1) and potassium content in the leaves, in the production of soybean cultivated in different straws and potassium doses in two crop seasons under Cerrado conditions in the region of Ceres, Goiás, Brazil. Two types of straw (Brachiaria and millet) and four potassium doses were evaluated. A randomized complete block design arranged in a 2x2x4 factorial scheme with four repetitions was used. Two crop seasons (2011/2012 and 2012/2013), two types of straw (Millet and Brachiaria), and four potassium doses (0, 30, 60, and 90 kg ha-1 of K2O using KCl as source) were evaluated. Phosphate fertilization was performed using 400 kg ha-1 of simple superphosphate, and the cultivar used was P98Y12. The largest plant height values were obtained by applying 90 kg ha-1 of K2O. The Brachiaria straw promoted a grain yield increase associated with the potassium doses increment. The highest grain yield was 4,353.90 kg ha-1, achieved by applying 65 kg ha-1 of K2O using millet straw. The highest grain yield reached was at the rate of 90 kg ha-1 of K2O, resulting in 5,208 kg ha-1. The greatest K accumulation in the leaf is provided by Brachiaria straw.

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

Nitrogen and potassium synergism influences the yield and quality of Dioscorea cayennensis

This study aimed to evaluate yield, quality, nematode incidence, chlorophyll content, and primary foliar macronutrients of yam in response to nitrogen and potassium fertilization. A complete randomized block design was used in a factorial scheme (5 x 5), with five nitrogen (0; 60; 120; 180 and 240 kg ha-1 of N) and five potassium doses (0; 60; 120; 180 and 240 kg ha-1 of K2O), with four replicates. The mass, total and commercial productivity of tubers, starch content, ash, leaf N, P, and K content, chlorophyll, and nematode incidence were evaluated. The average mass of tubers obtained was 1.935 kg with doses of 133 kg ha-1 of N and 105 kg ha-1 of K2O. The dose of 178 kg ha-1 of N promoted maximum total tuber productivity (22.56 t ha-1). The doses of 132 kg ha-1 of N and 118 kg ha-1 of K2O resulted in maximum productivity of commercial tubers with 20.35 t ha-1. Leaf N and K, starch, and ash contents were within the standards for yam. The incidence of Meloidogyne, Scutellonema, and Pratylenchus reduced with the increasing simple effect doses of N and K2O. The maximum chlorophyll content was obtained at the dose of 240 kg ha-1 of N. The nitrogen and potassium interaction, despite the antagonistic effects on the accumulation of foliar P and starch, increased the productivity and average mass of commercial tubers, consequently ensuring the profitability of yam cultivation.

Gypsum and potassium application to acid soils for maize (Zea mays L.) production in La Frailesca, Chiapas, Mexico

Introduction. Maize (Zea mays L.) production in La Frailesca region, Mexico, is limited by sandy soils, low in potassium (K), and with acidic arable layers and subsoils. There is information on the management of lime but not on amendments that could be used for subsoil acidity — such as gypsum — nor on the interactions between amendments for soil acidity and K fertilization. Objective. To evaluate the effects of K and gypsum on maize and on previously limed soils. Materials and methods. The evaluations were conducted in farmers’ fields in La Frailesca region, Chiapas (Mexico) in 2016 and 2017. Four gypsum rates (0, 1.25, 2.5 and 5 t ha-1) and four K rates (0, 60, 90, and 120 kg ha-1 as K2O) were factorially combined in a randomized block design, with three replicates. In both years, before the beginning of the experiments, dolomitic lime was applied to the experimental area following standard practices. Responses of crop yield, soil exchangeable K, Ca, Mg, and Al, and soil pH were obtained. Results. Maize yields increased with gypsum (stabilizing at 1.25-3.0 t ha-1), and K (stabilizing at 70-120 kg ha-1 of K2O) applications. In soils, K application increased exchangeable K content, while gypsum increased exchangeable Ca content and pH, and decreased exchangeable Al content. Liming increased pHCa and exchangeable Ca and Mg contents, and lowered the exchangeable Al content in the top 7.5 cm of soil. Conclusion. Soils with exchangeable K (≤0.3 cmolc kg-1) were responsive to K fertilization. The positive effects on yields from gypsum were probably linked to a greater Ca supply in the top 7.5 cm. These results are encouraging about the benefits of the combined application of dolomitic lime, gypsum, and K, but longer evaluations are needed to properly determine the effects of gypsum on subsoil acidity.

Productivity and quality of watermelon fruits as a function of doses potassium in the Western Amazon

Potassium is the nutrient most demanded by watermelon, performing various physiological and biochemical functions, and its availability in the soil influences the production and quality of fruits. However, there is no recommendation for specific fertilization for the state of Rondônia, which has limited the production and quality of the harvested fruits. The objective of this work was to evaluate the effects of potassium doses on the productivity and quality of watermelon fruits, cultivar Crimson Sweet, in southern Western Amazonia. The experiment was carried out at the Federal University of Rondônia, in the municipality of Rolim de Moura, in an experimental design in randomized blocks, with five treatments and four replications. The treatments were doses 0 (control), 50, 100, 150 and 200 kg ha-1 of K2O. The variables analyzed were fruit mass, longitudinal and transverse diameter of fruits, number of fruits per plant, soluble solids content, exocarp thickness and productivity. Potassium doses did not influence the mean mass and longitudinal and transverse diameter of the fruits. The number of fruits per plant increased linearly as a function of the potassium doses applied, and with 157 kg ha‑1 of K2O the highest values of °Brix were obtained. The dose of 147.2 kg ha-1 of K2O promotes yields 61.6% above the national average and 82% above the state average.

Biometric responses of sugarcane under high doses of vinasse

ABSTRACT Rational use of vinasse as a fertilizer in sugarcane cultivation is a good option to increase crop development and yield due to its nutritional support, properly dispose of the by-product, and reduce costs of mineral nutrition. However, in the field, controlling the amount of vinasse can be difficult, interfering in sugarcane development. In this sense, this study aimed to evaluate high doses of vinasse related to biometric responses in the initial growth phase of sugarcane plants. The experimental design was completely randomized, and the treatments consisted of five vinasse doses (0, 150, 300, 600, and 1200 m3 ha-1), with six replicates, except D0, three replicates, and one dose of mineral fertilizer with 70 kg ha-1 of N, 120 kg ha-1 of P2O5 and 90 kg ha-1 of K2O, with three replications. The biometric variables were evaluated in the following sequence: number of tillers per pot from 60 to 150 days after planting (DAP), plant height, number of green and dry leaves from 90 to 210 DAP, stem diameter, leaf area, and fresh and dry biomasses of roots and shoots at 210 DAP. Vinasse increased the biomass production through the number of tillers and the number of leaves compared to mineral fertilizer, promoting greater growth up to the dose of 600 m3 ha-1. The vinasse dose of 1200 m3 ha-1 decreased the plant height.

CHEMICAL FERTILIZATION THROUGH FERTIRRIGATION IN THE EVALUATION OF THE BIOCHEMICAL CHARACTERISTICS OF THE WATERMELON FRUITS

The objective of this work was to evaluate the effects of splitting in three different doses of phosphorus and potassium, combined with each other, and it was applied fertirrigation in watermelon crop, and to evaluate their effects on fruit quality. The statistical was in a complete randomized block design, and the treatments were arranged in a factorial scheme (3 x 3) in subdivided splits, resulting in 9 treatments with tree replications, totaling 27 plots in the experimental area. In the horizontal plots the three doses of phosphorus fertilization (100, 150 and 300 kg.ha-1 of P2O5) were randomly allocated, and in the subplots the three potassium doses (50, 100 and 200 kg.ha-1 of K2O), were applied in fertirrigation. The cultivar used was Crimson Sweet. Seventy-Six days after planting (DAP) the biochemical characteristics of watermelon fruits were evaluated: total soluble solids (TSS), total treatable acidity (TTA) and potential of hydrogen (pH). According to the results, it was verified that only the chemical value of the TSS fruits, presented significant statistical differences between the studied doses because of the different source of fertilization K and P increased the soluble solid contents, the content of reducing sugars, and decreased pH. It was observed the different doses of K and P did not influence in the fruit quality parameters when it was analyzed separated: TTA and pH but the TTA values are according to consumer market standards. The best doses in order to economy of fertilizer were (150 kg ha-1 de P2O5 e 50 kg ha-1 of K2O).

Efficiency and Response to Phosphorus Use of Corn Cultivars in the Tropical Climate

Aims: The present study evaluated the efficiency and response to phosphorus (P) use of corn cultivars in the tropical climate in southern Para State, Brazil.
 Study Design: Two experiments were carried out, in low P (50 kg ha-1) and high P (200 kg ha-1) applications in Randomized block design (RBD), three replicates, and fourteen cultivars were used for the experiment.
 Place and Duration of Study: The experiment was carried out in the 2019-20 harvest at Sitio Vitoria (8º18'32" S, 50º36'58" W), located in the municipality of Santa Maria das Barreiras, a southern region of Para state, Brazil.
 Methodology: Phosphate fertilization was used in the sowing groove. In low P, 50 kg ha-1 of P2O5 were applied, and in high P were 200 kg ha-1 of P2O5. The source was simple superphosphate (18% P2O5). The dose in high P was defined to achieve high yields and considering the nutrient content in the soil, in low P the dose was well below. Nitrogen and potassium fertilization in cover were divided: 50% in V4 and 50% in V8. Doses of 150 kg ha-1 of N and 90 kg ha-1 of K2O were used, and fertilizers were used: urea (43% N) and potassium chloride (60% K2O).
 Results: The highest means were: 8,710 kg ha-1 efficiency and 29.78 kg kg-1 response. The efficient cultivars were: ORION, BR 2022, CR 120, AL BANDEIRANTE, M 274, BRS 3046, and AG 8088. And those considered responsive were: BM 3061, BR206, CATIVERDE 02, BR 205, ANHEMBI, BR 2022, and BRS 3046.
 Conclusion: The cultivar BR 2022 and BRS3046 showed high efficiency and also a response to phosphorus use.

Potassium sources and calcium and magnesium doses in carrot crop fertilization

ABSTRACT Fertilization has an important influence on carrot productivity and on the quality of the produced root, being responsible for most of the production cost of the crop. In this context, we evaluated the use of potassium (K) sources associated with calcium (Ca) and magnesium (Mg) doses in carrot cultivation. In a randomized block design in a triple factorial scheme (2x2x2), we evaluated two doses and sources of potassium [potassium chloride (KCl), 120 kg ha-1 of K2O; potassium sulfate (K2SO4) 120 kg ha-1 of K2O + 42,5 kg ha-1 of S]; Two doses of Mg [magnesium sulfate (MgSO4), zero kg ha-1 of Mg; 25 kg ha-1 of Mg + 34,2 kg ha-1 of S]; two doses of the commercial algae product Lithothamnium calcareum as an alternative source of Ca [zero kg ha-1 of seaweed; 200 kg ha-1 of seaweed (24 kg ha-1 of Ca)], all with six replications. Total productivity, 3A, commercial and percentage of discard carrot were evaluated. Regardless of the source of K used, the carrot production was median (above 40 t ha-1), with no application of Ca or Mg. The application of 25 kg ha-1 of Mg and zero Ca altered the Ca:Mg ratio in the soil and provided a significant increase in yield when KCl was used. The association of L. calcareum algae with KCl reduces total yield and increases carrot disposal.

Nutrient cycling of different plant residues and fertilizer doses in broccoli cultivation

ABSTRACT The decomposition and release of nutrients from plant residues that precede the cultivation of vegetables can positively affect the morphological parameters and crop productivity. The objective of this study was to evaluate the effects of plant residue decomposition and the cycling of macro and micronutrients of four cover crops preceding the broccoli production (single head Avenger hybrid). A 4x3 factorial scheme was implemented including four cover crops: signal grass (SG), pearl millet (PM), sunn hemp (SH), mixture PM+SH; and three doses of mineral fertilizer: 0, 50 (200 kg ha-1 of P2O5, 50 kg ha-1 of K2O, 75 kg ha-1 of N) and 100% of the recommended fertilizer dose (400 kg ha-1 of P2O5, 100 kg ha-1 of K2O and 150 kg ha-1 of N). Fresh (FB) and dry biomass (DB), residue decomposition, nutrient cycling of cover crops, the number of leaves, head height (HH), stem diameter (SD), head diameter (HD), head fresh-biomass (FB), head dry biomass (DB) and broccoli yield were evaluated. The FB production from PM (25.9 t ha-1), SG (23.3 t ha-1) and mixture PM+SH (23.9 t ha-1) were similar, while the largest production of DB occurred in the SG (11.9 t ha-1). The lowest rate of decomposition and the greatest half-life time of residues occurred where PM was present. The accumulation and nutrient cycling follow the sequence K>N>Ca>Mg>P>S and Mn>Zn>B>Cu for all cover crop treatments evaluated. The highest SD (51.95; 51.44 and 50.67 mm), HD (187.97; 187.41 and 183.48 mm), FB (1.01; 1.00 and 0.97 kg), DB (0.08; 0.07 and 0.07 kg) and broccoli yield (25.3; 24.9 and 24.7 t ha-1) was observed in the 100% dose of mineral fertilizer and on the residues of SH or PM+SH mixture, respectively.

Nitrogen and potassium fertilization on cabbage biometrics and foliar nutritional levels

Among the most absorbed nutrients by cabbage, nitrogen (N) and potassium (K) are the most extracted; thus, the objective of this study was to evaluate the responses of N and K fertilization on the cabbage biometrics and foliar levels of macro and micronutrients. Four N doses (0, 75, 150, 300 kg ha-1 of N) and four K doses (0, 75, 150, 300 kg ha-1 of K2O). Biometrics of cabbage head (height, circumference and diameter) and productivity were evaluated. The cabbage levels of macro and micronutrients were also evaluated in leaves of plants at the phenological stage of head-formation. Nitrogen fertilization did not significantly affect the variables evaluated mostly due to the great natural fertility of the experimental soil area. This lack of response highlights the importance of constant monitoring of the nutritional status of the productive area to avoid non-necessary N fertilization. The lowest Mg leaf content was observed at 88 kg ha-1 of K2O, after which the Mg leaf content increased. The foliar Zn was reduced in doses after 133 kg ha-1 of K2O. The cabbage head diameter and circumference decreased with the increase of the K2O doses. The cabbage head height increased up to 128 kg ha-1 of K2O. The decreasing sequence of the macro and micronutrient levels in cabbage leaves followed the sequence K>Ca>N>S>Mg>P and Mn>Fe>B>Zn>Cu regardless of the level of the factors applied.