Reclaimed wastewater: Impact on soil-plant system under tropical conditions

This study investigated the ionic speciation of reclaimed urban wastewater (RWW), and the impact of increasing RWW irrigation rates on soil properties and plant nutrition under field conditions. Most RWW elements (>66%) are readily available as NH(4)(+), Ca(2+), Mg(2+), K(+), SO(4)(2-), Cl(-), H(3)BO(3), Mn(2+) and Zn(2+), but in imbalanced proportion for plant nutrition. Lead, Cd, Cr and Al in RWW are mostly bounded with DOM or OH. Irrigation with RWW decreased soil acidity, which is beneficial to the acidic tropical soil. Although RWW irrigation builds exchangeable Na(+) up, the excessive Na(+) was leached out of the soil profile after a rainy summer season (>400 mm). Benefits of the disposal of RWW to the soil under tropical conditions were discussed, however, the over irrigation with RWW (>100% of crop evapotranspiration) led to a nutritional imbalance, accumulating S and leading to a plant deficiency of P and K. (C) 2011 Elsevier B.V. All rights reserved.

Risk factors associated with leptospirosis in dairy goats under tropical conditions in Brazil

Serum samples from 248 adult dairy goats from 13 flocks with lowered fertility farmed in the Rio de Janeiro region of Brazil were examined for Leptospira antibodies by MAT with 24 serovars, cut off 100. A questionnaire was completed for each herd. Antibodies were detected in 20.8% of these goats, mainly to serovar Hardjo. Risk factors associated with seroprevalence to leptospirosis were the frequency of professional veterinary supervision (OR = 2.35), climate (OR = 2.63) and grazing for more than 2 h a day. Flock factors as size, type of milking and offering of food supplementation, as well as the location and topography, the type of animal housing or the presence of silos did not significantly affect seroprevalence. We suggest that a successful control program for goat leptospirosis should include a complete investigation of herd management practices, which could influence in the occurrence of the infection. (C) 2007 Elsevier Ltd. All rights reserved.

Limitations to photosynthesis of lettuce grown under tropical conditions: alleviation by root-zone cooling

Aerial parts of lettuce plants were grown under natural tropical fluctuating ambient temperatures, but with their roots exposed to two different root-rone temperatures (RZTs): a constant 20 degreesC-RZT and a fluctuating ambient (A-) RZT from 23-40 degreesC, Plants grown at A-RZT showed lower photosynthetic CO2 assimilation (A), stomatal conductance (g(s)), midday leaf relative water content (RWC), and chlorophyll fluorescence ratio F-v/F-m than 20 degreesC-RZT plants on both sunny and cloudy days. Substantial midday depression of A and g(s) occurred on both sunny and cloudy days in both RZT treatments, although F-v/F-m did not vary diurnally on cloudy days. Reciprocal temperature transfer experiments investigated the occurrence and possible causes of stomatal and non-stomatal limitations of photosynthesis. For both temperature transfers, light-saturated stomatal conductance (g(s) (sat)) and photosynthetic CO2 assimilation (A(sat)) were highly correlated with each other and with midday RWC, suggesting that A was limited by water stress-mediated stomatal closure, However, prolonged growth at A-RZT reduced light- and CO2-saturated photosynthetic O-2 evolution (P-max), indicating non-stomatal limitation of photosynthesis. Tight temporal coupling of leaf nitrogen content and P-max during both temperature transfers suggested that decreased nutrient status caused this non-stomatal limitation of photosynthesis.

Simulating maize yield in sub‑tropical conditions of southern Brazil using Glam model

The objective of this work was to evaluate the feasibility of simulating maize yield in a sub‑tropical region of southern Brazil using the general large area model (Glam). A 16‑year time series of daily weather data were used. The model was adjusted and tested as an alternative for simulating maize yield at small and large spatial scales. Simulated and observed grain yields were highly correlated (r above 0.8; p<0.01) at large scales (greater than 100,000 km²), with variable and mostly lower correlations (r from 0.65 to 0.87; p<0.1) at small spatial scales (lower than 10,000 km²). Large area models can contribute to monitoring or forecasting regional patterns of variability in maize production in the region, providing a basis for agricultural decision making, and Glam‑Maize is one of the alternatives.

Effects of row spacing on productivity and nodulation of two soybean varieties under hot sub-moist tropical conditions in south-western Ethiopia

The objective of this study was to determine the optimum row spacing to improve the productivity of two soybean (Glycine max L.) varieties under the tropical hot sub-moist agroecological conditions of Ethiopia. A two-year split-plot design experiment was conducted to determine the effect of variety (Awasa-95 [early-maturing], Afgat [medium-maturing]) and row spacing (RS: 20, 25, 30, 35, 40, 45, 50, 55, 60 cm) on the productivity, nodulation and weed infestation of soybean. Seed and total dry matter (TDM) yield per ha and per plant, and weed dry biomass per m^2 were significantly affected by RS. Soybean variety had a significant effect on plant density at harvest and some yield components (plant height, number of seeds/pod, and 1000 seed weight). Generally, seed and TDM yield per ha and per plant were high at 40 cm RS, and weed dry biomass per m^2 was higher for RS >= 40 cm than for narrower RS. However, the results did not demonstrate a consistent pattern along the RS gradient. The medium-maturing variety Afgat experienced higher mortality and ended up with lower final plant density at harvest, but higher plant height, number of seeds per pod and 1000 seed weight than the early-maturing variety Awasa-95. The results indicate that 40 cm RS with 5 cm plant spacing within a row can be used for high productivity and low weed infestation of both soybean varieties in the hot sub-moist tropical environment of south-western Ethiopia.

Simulating maize yield in sub-tropical conditions of southern Brazil using Glam model

The objective of this work was to evaluate the feasibility of simulating maize yield in a sub‑tropical region of southern Brazil using the general large area model (Glam). A 16‑year time series of daily weather data were used. The model was adjusted and tested as an alternative for simulating maize yield at small and large spatial scales. Simulated and observed grain yields were highly correlated (r above 0.8; p<0.01) at large scales (greater than 100,000 km2), with variable and mostly lower correlations (r from 0.65 to 0.87; p<0.1) at small spatial scales (lower than 10,000 km2). Large area models can contribute to monitoring or forecasting regional patterns of variability in maize production in the region, providing a basis for agricultural decision making, and Glam‑Maize is one of the alternatives.

Alternative body sites for heat stress measurement in milking cows under tropical conditions and their relationship to the thermal discomfort of the animals

This study was conducted to determine the relationship among temperatures measured at different anatomical sites of the animal body and their daily pattern as indicative of the thermal stress in lactating dairy cows under tropical conditions. Environmental dry bulb (DBT) and black globe (BGT) temperatures and relative humidity (RH) were recorded. Rectal temperature (RT), respiratory frequency (RF), body surface (BST), internal base of tail (TT), vulva (VT) and auricular temperatures (AT) were collected, from 37 Black and White Holstein cows at 0700, 1300 and 1800 hours. RT showed a moderately and positive correlations with all body temperatures, ranging from 0.59 with TT to 0.64 with BST. Correlations among AT, VT and TT with RF were very similar (from 0.63 to 0.64) and were greater than those observed for RF with RT (0.55) or with BST (0.54). RF and RT were positively correlated to TT (0.63 and 0.59, respectively), AT (r = 0.63 for both) and VT (r = 0.64 and 0.63, respectively). Positive and very high correlations were observed among AT, VT and TT (from 0.94 to 0.97) indicating good association of temperatures measured in these anatomical sites. Correlations of BST with AT and VT were positive and very similar (0.71 and 0.72, respectively) and lower with TT (0.66). The AT, TT, VT and BST presented similar patterns and follow the variations of DBT through the day. Temperatures measured at different anatomical sites of the animal body have the potential to be used as indicative of the thermal stress in lactating dairy cows.

Human-animal interaction, stress, and embryo production in Bos indicus embryo donors under tropical conditions

This study investigated the effect of human-animal interaction (HAI) and the stress response on the quality of embryo production in superovulated Nelore (Bos indicus) cattle, under tropical conditions. Thirty-two females underwent a superovulation protocol for 5 days. Cortisol concentrations were determined in blood plasma collected on days 0, 4, and 5. Artificial insemination was performed on days 4 and 5, and nonsurgical embryo flushing on day 11. Embryo production and viability were determined. Human stimulation, animal behaviors, accidents, and handling time were recorded to assess HAI. Cattle age was negatively correlated with accidents, frequency of aversive behaviors, and negative stimuli by stockperson during transit through corral compartments to receive superovulation treatments. The factor analysis revealed two distinct groups. The first group was called stressed and had higher cortisol concentration than the nonstressed group, 16.0 +/- 2.1 and 12.5 +/- 1.0 ng/mL, respectively. Comparisons between these groups showed that the frequency of voice emissions by the stockperson and the number of accidents were higher in the stressed group, and also, the mean handling time was longer in the stressed group than for the nonstressed. As a result, viability rate of the embryos was 19% lower in the stressed group (P < 0.05). This indicates that intensive negative HAI is likely related to stress, which affects embryo production in a superovulation program.

Influence of different supplements and sugarcane (Saccharum officinarum L.) cultivars on intake, digestible variables and methane production of dairy heifers under tropical conditions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Gonadic Sperm Reserve in Buffaloes Created under Tropical Conditions

The objective of the present study was quantifying the spermatic production per gram and daily rate of the testicular parenchyma. Testis of 12 crossbred Murrah buffaloes aged 24 to 48 months created under extensive conditions in the State of São Paulo/Brazil were analyzed. Animals were divided into groups based on the testicular shape (long and long-moderate) and testicular sides (right and left) and the studied parameters were: length and testicular width, weight and volume of the albuginea and mediastinum and net weight of the testicular parenchyma, gonadic sperm reserves, spermatic production/g of testicular parenchyma, daily spermatic production/g, total daily spermatic production, resulting into the values: 8.16 +/- 0.87 and 4.29 +/- 0.50 cm; 9.09 +/- 1.91 g and 8.77 +/- 1.88 mL; 0.97 +/- 0.39 g and 0.90 +/- 0.38 mL; 112.91 +/- 18.85 g; 14.32 x 10(9) +/- 0.15; 13.42 x 10(6) +/- 0.17; 27.40 x 10(6) +/- 0.35 and 2.92 x 10(9) +/- 0.30, registering no difference between right and left testis in relation to the parameters (P>0.05). There was no relation between testicular biometry and spermatic production (P>0.05). According to the obtained values, all animals were considered sexually mature and presented an efficient spermatic production per gram of testicular parenchyma and total daily production.

Evaporative cooling and cutaneous surface temperature of Holstein cows in tropical conditions

Foram estudados os efeitos da temperatura cutânea (Ts) sobre a taxa de termólise por evaporação cutânea (Es) de vacas Holandesas cronicamente expostas ao sol, considerando a pigmentação do pelame. Dezesseis vacas puras de origem foram medidas quanto à evaporação e à temperatura cutâneas às 13 h, após 6 horas de exposição ao sol, no mesmo local (flanco, pescoço e glúteo) e considerando separadamente as malhas negras e as brancas. A evaporação cutânea foi medida por meio de cápsula ventilada. Nas áreas negras a taxa de sudação (138,9 ± 8,5 g.m-2.h-1), a taxa de termólise por evaporação cutânea (93,3 ± 5,7 W.m-2) e a temperatura da superfície cutânea (33,1 ± 0,2°C) foram maiores que nas áreas brancas (109,5 ± 9,7 g.m-2.h-1, 73,6 ± 6,5 W.m-2 e 32,6 ± 0,2°C, respectivamente). Há uma relação exponencial entre evaporação e temperatura cutâneas, que pode ser representada pela equação Es = 31,5+3,67 exp{(Ts-27,9)/2,19115}, com coeficiente de determinação r²=0,68. A taxa de termólise por evaporação cutânea permanece quase constante (cerca de 48 W.m-2) até que a temperatura cutânea atinge aproximadamente 31°C.

Environmental and genetic variation of the effective radiative properties of the coat of Holstein cows under tropical conditions

Morphological characteristics, coat effective radiative properties, and the percentage of white colour were measured in the coats of 973 Holstein cows, and estimates of the genetic parameters were obtained for these traits, except morphological characteristics. The results showed that white coats are more dense with long, thin hairs, while the black coats are less dense with short, thick hairs. Effective transmissivity is greater in the less-dense coats with short, thin hairs, independently of coat colour. Effective reflectivity depends more on the variation in the radiative properties of the coat and skin surface rather than on the morphological characteristics of the coat. Effective absorptivity is greater in black and dense coats with long, thick hairs, than in the white and less-dense coat with short, thin hairs. All heritability estimates were of low magnitude, except for the percentage of white coat colour.

Potential hydroponics systems for seed potato production in tropical conditions

In tropical conditions such as Brazil, depending on the local altitude, potatoes can be planted and harvested in every month of the year successively, which favors pest and disease incidence, especially aphids transmission viruses. Therefore, obtaining good yield depends on constant pest and disease control and quality potato seed acquisition. One of the main strategies to increase a healthier seed potato multiplication rate and production is the use of hydroponic systems, with or without substrates, in channels, pots or boxes. In 2005 and 2008, researches investigated several hydroponic systems with and without the use of substrates. In the hydroponic systems without substrate, the aeroponic system resulted in the highest multiplication rate, with 47 tubers plant-1 compared to NFT and DFT, 35 and 37 tubers plant-1, respectively. With the use of substrates, the pot system obtained better results, reaching 12 tubers plant-1, followed by the capillary system and boxes, with 8 and 7 tubers plant-1, respectively. Potato seed production was influenced by hydroponics systems. Among hydroponic systems with substrate, the pots were shown as the best option. However, higher yields were obtained in the hydroponics systems without substrate, with the aeroponic system that provided the best results.