Paulo Roberto Gomes Pereira

Corn crop characteristics under nitrogen, molybdenum and zinc fertilization

Fertilization is the factor that presents the highest contribution to corn yield, and may also affect grain quality. The objective of this work was to evaluate, in a an Ultisol, the fertilization with N, Mo and Zn on to determine yield and maize grain quality (protein and mineral nutrient contents) and to determine the best sampling time to analyse organic-N, NO3--N and total-N (NO3--N + organic-N). In addition, nutrient concentrations in maize grain were related to leaves. The experiment was a factorial 4x2x2 in a randomized complete block design with four replications in which the factors were: four N raes (0, 70, 140 and 210 kg ha-1), two of Mo (0 and 90 g ha-1) and two of Zn (0 and 3 kg ha-1). Leaves were sampled 25, 45 and 63 days after emergency (DAE). Tissue and grain were milled and analysed, and organic-N, NO3--N, total-N, protein, P, K, Ca, Mg, S, Zn, Fe, Cu and Mn contents were evaluated. Zinc and molybdenum applications and their interactions with N did not affect any yield characteristics. The weight of thousand grains, the number of ears per plant, the weight of ears with and without straw, and yield increased with increased rates. Maximum yield (8.58 t ha-1) was obtained with 201.2 kg ha-1 N. Protein content and analysed nutrients in grain increased with increasing N rate. Mo fertilization raised protein content, while Zn application increased protein content in grains. The critical levels of total-N were 2.73 and 2.00 dag kg-1 at 45 and 63 DAE. The best traits for diagnosis index and yield prediction was the organic-N content at 45 DAE. In general, grain mineral content was positively correlated with leaft mineral content at 63 DAE.

Critical chlorophyll, total nitrogen, and nitrate‐nitrogen in leaves associated to maximum lettuce yield

Abstract An experiment was conducted to establish chlorophyll, nitrate‐nitrogen (NO3‐N), and total nitrogen (N) critical concentrations in lettuce (Lactuca sativa) leaves that are associated with maximum dry matter yield. Six N levels (0, 60, 120, 240, 480, and 960 mg.kg‐1 soil) as ammonium nitrate (NH4NO3) were applied in a randomized block design with four replications. Two wrapper leaves were collected at the eighth‐leaf stage and analyzed for their chlorophyll a+b and total N contents. Forty‐five days after transplanting, plants were harvested, dried, and analyzed for their NO3‐N and total N contents. Critical levels associated with maximum lettuce yield at the eighth‐leaf stage were: 1,837 mg chlorophyll kg‐1 fresh weight and 4.27 g N 100 g‐1 dry matter, and at harvest: 6,361 mg NO3‐N kg‐1 dry weight and 3.75 g N 100 g‐1 dry matter. In the soil, N levels associated to maximum plant dry weight were 34 mg NO3 ‐N kg‐1 and 390 mg N kg‐1.

Deficiência de macronutrientes em estévia: sintomas visuais e efeitos no crescimento, composição química e produção de esteviosídeo

This experiment was carried out to describe visual symptoms of macronutrients defi- ciencies in Stevia rebaudiana, and the effects of these deficiencies on growth, chemical composition and stevioside production. The symptoms were: yellowing with -N; dark green leaves with -P; clorotic, mottled, and necrotic leaves, with -K; apical necrosis, with -Ca; leaves with clorosis and necrosis in inverted iVi shape, with -Mg, and small pale green leaves, with -S. N, K, and Mg deficiencies reduced the leaf growth, therefore the plant marketable part. Mg deficiency caused greater reduction on the development of the radicular system. N, P, K, and S deficiencies decreasead the shoot:root dry weigth ratio, while Mg deficiency increased it. All deficiencies decreased the absorption of macronutrients, except of Ca, which reduced only the absorption of Ca, and K, that did not affect the absorption of Mg and S. The chemical content of the last five fully expanded leaf pairs showed good correlation with the plant nutritional status. The deficiencies of K, Ca, and S decreased the concentration of stevioside while all deficiencies, except of P, decreased the stevioside content.

Produtividade, acúmulo de nitrato e estado nutricional de cultivares de alface, em hidroponia, em função de fontes de nutrientes

Foram avaliados a produtividade, acumulo de nitrato e estado nutricional das cultivares de alface Regina, Baba de Verao e Grandes Lagos em cultivo hidroponico. O experimento foi conduzido no outono, de 25/03 a 20/05/99 em estufa da UFV. Foram avaliados dois conjuntos de fontes de nutrientes para compor as solucoes nutritivas de crescimento vegetativo, que continham: 13,6; 1,0; 7,0; 4,48; e 2,5 mmol L-1 de N, P, K, Ca e Mg, respectivamente. O enxofre foi fornecido na concentracao de 3,5 ou 2,5 mmol L-1 e os micronutrientes nas concentracoes de 45; 32; 46; 2; 0,9; e 0,2 mmol L-1 para Fe, Mn, B, Zn, Cu e Mo, respectivamente. A solucao 1 forneceu 21,9% de N na forma amoniacal, e a solucao 2, 100% de N na forma de nitrato. As fontes de P empregadas foram fosfato monoamonico e fosfato monopotassico para as solucoes 1 e 2 respectivamente, sendo que esta variacao implicou no uso de diferentes quantidades de KCl nas solucoes, o que proporcionou concentracoes diferentes de Cl, apresentando-se 6,76 e 2,18 mmol L-1 para as solucoes 1 e 2, respectivamente. O cultivo foi feito em recipiente plastico com 8L de capacidade, contendo tres plantas. Os recipientes foram arranjados de modo que se obtivesse espacamento de 0,22 m entre plantas. O delineamento experimental utilizado foi blocos ao acaso com seis repeticoes, em arranjo fatorial 2 x 3 (solucoes x cultivares). Cada parcela foi constituida por tres plantas. Foram avaliados o peso da materia fresca da parte aerea, folhas, raizes e caule, numero de folhas, comprimento do caule, porcentagem de materia seca das folhas e estado nutricional da planta. A cv. Regina produziu 233 g planta-1 e a cv. Baba de Verao 193 g planta-1. Os resultados obtidos para a cultivar Grandes Lagos nao foram satisfatorios nas condicoes do experimento. A solucao 1 proporcionou menores concentracoes de nitrato para as cultivares Grandes Lagos (1082 mg kg-1 de materia fresca) e Regina (1092 mg kg-1 de materia fresca). As plantas apresentaram altas concentracoes de Mn, mas sem sintomas de toxidez. Em geral, a nutricao das plantas foi adequada para os dois conjuntos de fontes de nutrientes testados.

Assessment of Nitrogenized Nutrition of Citrus Rootstocks Using Chlorophyll Concentrations in the Leaf

Abstract The objective of this study was to evaluate the nitrogen (N) nutrition in lemon tree rootstocks “Cravo” (Citrus limonia Osbeck) and “Volkameriano” (Citrus volkameriana Ten. e Pasq.) and mandarin tree rootstocks “Cleopatra” (Citrus reshni Hort. ex Tan.) and “Sunki” (Citrus sunki Hort. ex Tan.), using the chlorophyll concentration in the rootstock leaves, grown in 3.0 dm3 capacity container in a greenhouse. Nitrogen was added to the lemon tree substrate at 0, 158, 316, 474, and 632 mg/dm3, and 0, 193, 386, 579, and 772 mg/dm3 were added to the mandarin trees. These N quantities were divided into 20 urea applications for the lemon trees and 24 applications for the mandarin trees during the experiment. The experiment consisted of a factorial arrangement (4 × 5), carried out in a randomized block design, with three replications. The experimental unit consisted of four containers, with one plant per container. The chlorophyll concentration, measured by the Arnon standard method and by the SPAD‐502 portable apparatus, were affected by the N. In general, the rootstocks presented little variation in the chlorophyll concentration measured in the leaves. These values were positively correlated with the growth characteristics and N concentration in the leaves, indicating that N can be monitored using such determinations.

Avaliação de métodos de correção do estande para estimar a produtividade em milho

The objective of this work was to determine the method of stand correction more adequate to estimate productivity in cornfields of 33 varieties in eight situations. The methods tested were: without correction, rules of three, method of Zuber, covariance of medium stand, covariance of ideal stand, proposed by Cruz, proposed by Vencovsky & Cruz, the method proposed in this work, which consisted of a stratified correction based on the combined productivity for the characteristic stand, by Scott Knotts test. The methods proposed in this work, covariance of ideal stand and that proposed by Vencovsky & Cruz were considered the most appropriate ones, because they presented lower values for the coefficient of variation and high value of F, which was confirmed by the low values of Pi and Pi multivariate in the combined analysis. The methods rules of three and proposed by Cruz showed the highest averages of productivity, which overestimate the real value of the average production. The method proposed in this work was efficient to correct the productivity of the corn varieties, once the most productive varieties were also those with higher potential to leave descendants, measured by the average stand.

Eficiência nutricional para fósforo em linhagens de pimentão

Ten sweet pepper lines were screened for phosphorus efficiency. An experiment was carried out in the greenhouse in pots filled with 5 dm3 of clayey latosol soil samples. The treatments followed a randomized complete block design, in a factorial layout (10 x 5 x 4), comprising ten lines, five doses of P (0; 250; 500; 750 and 1,000 mg of P/kg of soil) and four replications. Results showed genetic variability among lines for P-efficiency, characterized mainly by rooting efficiency, P-uptake and P-use efficiency. Low differences in the P- translocation efficiency were observed. Higher rooting efficiency was not translated into higher acquisition of P from the soil, which suggests that P-absorption was influenced by morphologic and physiologic characteristics of the root system. The L10 line showed high P-efficiency uptake and utilization, followed by the L8 line. The L1, L2 and L6 lines, were the least efficient in the P-utilization. The other lines showed variable performance in P-efficiency, according to the index used. The large variability observed might be explored in genetic improvement programs aiming to increase the nutritional efficiency for P.

CAPACIDADE DE COMBINAÇÃO ENTRE LINHAGENS DE PIMENTÃO DIFERINDO NA TOLERÂNCIA AO BAIXO TEOR DE FÓSFORO NO SOLO

Six lines of sweet pepper (Capsicum annuum L.) differing in tolerance to low phosphorus (P) content in the soil, their F1 hybrids and reciprocals, obtained from a complete diallel cross, were assessed under greenhouse conditions in order to estimate their combining abilities for total dry matter accumulation (shoot) dry matter, root dry matter, root (shoot) ratio, leaf area, plant height, total P content in the plant and P translocation coefficient. Both general (GCA) and specific (SCA) combining abilities were statistically significant with quadratic component associed to SCA which was always greater in magnitude than GCA for all traits, showing a predominance of non-additive genic effects in crosses. In addition to high positive GCA estimates, the tolerant lines to low P availability were the most divergent and their hybrids showed high average values for most of the assessed traits, while an opposite behaviour was observed in the tolerant lines. Considering the performance of the lines, the heterosis and the SCA effect, the following are promissing combinations: P-141-190--F16 x P-142-403-F11, P-142-215-F15 x P-142-270-F12, P-141-152-F14 x P-142-215-F15, P-141-152-F14 x P-142-403-F11 and P-141-150-F10 x P-141-152-F14. No difference was found among reciprocal crosses in relation to the assessed traits.

Critical potassium concentration and potassium/ calcium plus magnesium ratio in potato petioles associated with maximum tuber yields

Abstract In order to establish critical potassium (K) concentration levels and K/calcium (Ca) plus magnesium (Mg) [K/Ca+Mg] ratios in potato petioles associated to maximum total tuber yields, an experiment was conducted under Brazilian conditions. Six K levels (0, 60, 120, 240, 480, and 960 kg K2O/ha as potassium sulphate) were applied in a randomized complete block design experiment with four replications. Baraka potato tubers were seeded, spaced 0.8 x 0.3 m, following the agronomic cultural practices recommended for the crop. After 48 days from plant emergence, plant tissue samples was collected from each plant, the youngest fully expanded leaves (YFEL) and the oldest but not senescent leaves (ONSL). Petioles from these leaves were analysed to their K, Ca, and Mg contents. At harvest, total, high grade, and weight tuber yields were increased to 733, 719, and 660 g/plant for the 353, 335, and 384 kg K2O/ha levels, respectively. These yields are double the Brazilian potato yield average. Petiole Ca and Mg...

Tolerância de genótipos de pimentão ao baixo teor de fósforo no solo

Twenty two genotypes of sweet pepper (Capsicum annuum L.) were grown in pots containing 2.45 dm3 soil, in which six phosphorus (P) levels were applied (25, 50, 100, 200, 300 and 600 mg.dm-3 P). For each P level, the genotype performance was evaluated according to the characteristics expressing growth and nutritional efficiency. For several P levels, there was an occurrence of great differences among genotypes either in total dry matter accumulation and other characteristics related to growth, whereas low differences were observed in the nutritional characteristics. Among all P levels applied, 200 mg.dm-3 P was the most adequate for both identification of genotypes which are tolerant to low P availability and genetic studies, for its experimental accuracy and greater genotypic variability provided. By comparing the averages of total dry matter and based on discriminatory functions (multivariate analysis technique proposed by T. W. Anderson), six genotypes were identified as tolerant, ten as moderately tolerant and six as intolerant to low P contents. Apparently, only one factor was responsible for the difference in growing, which was observed between tolerant and intolerant genotypes. The tolerant genotypes which showed to be 2.34 times more efficient in producing total dry matter, also accumulated 2.38 times more P in the average, than those intolerant, probably due to greater biomass of tolerant-genotype roots. Differences in internal P use did not contribute for the differences between tolerant and intolerant genotypes.