Efeitos da proteção solar e do manejo de água na fisiologia e produção de pomar de laranja ‘Pêra’ em clima subúmido

Citrus trees require a balanced and adequate supply of macronutrient and micronutrient elements for high yield and fruit quality. Foliar nutrient analysis has been widely used in fruit-tree nutrient diagnosis and fertilization calculation. However, there is no information on ways to produce optimal fruit quality in sweet oranges. In the present study, fruit and leaf samples were collected from 120 ‘Bingtang’ sweet orange [Citrus sinensis (L.) Osbeck] orchards during four consecutive years (2019–2022). Parameters of leaf nutrition and fruit quality were analyzed based on these samples. Diagnostic results based on leaf classification standards indicated that the most deficient elements were Ca, Mg, and B, followed by N and Zn. Fruit quality, determined by single fruit weight (SFW), fruit shape index (FSI), total soluble solids (TSS), titratable acidity (TA), vitamin C (Vc), and maturation index (MI = TSS/TA) during fruit maturation, exhibited inconsistent responses to leaf mineral nutrition concentrations. The leaf-nutrient optimum values for high quality of the ‘Bingtang’ sweet orange fruit were ranges of 2.41–4.92% N, 0.10–0.28% P, 1.30–2.11% K, 2.99% Ca, 0.26–0.41% Mg, 340–640 mg/kg S, 89.65–127.46 mg/kg Fe, 13.48–51.93 mg/kg Mn, 2.60–13.84 mg/kg Cu, 15.59–51.48 mg/kg Zn, and 53.95 mg/kg for B. These results suggest the leaf-nutrient optimum values for diagnosis can be used not only to identify the nutrient constraints but also to provide guidance for the establishment of fertilization regimes in citrus cultivation.

Evaluation by PCR of Xylella fastidiosa subsp. pauca transmission through citrus seeds with special emphasis on lemons (Citrus limon (L.) Burm. f)

This study investigated the yield and quality response of soybean [Glycine max (L.) Merr.] to full and deficit irrigation applied at different growth stages under sub-humid climate conditions over a two-year period. A rain-fed (non-irrigated) treatment and 13 different irrigation treatments (1 full and 12 deficit irrigations) were applied to soybeans at four critical development stages: vegetative (V), flowering (F), pod formation (P) and seed enlargement (S). Deficit irrigation had a significant effect on seed yield, crude oil content, crude protein content and various agronomic parameters. The highest seed yield (4004 kg ha-1) was obtained with full irrigation (based on the replenishment of 100% of soil water depletion from a soil depth of 90 cm at 7-day intervals throughout the development period) and the lowest (1974 kg ha-1) with the rain-fed treatment, with a 50.6% difference in average yield between full irrigation (VFPS) and rain-fed treatments. The rain-fed treatment also resulted in the lowest crude oil content (19.1%) and the highest crude protein content (33.6%). As a result, it may be concluded that while VFPS treatment may be the best choice for maximum yield under local conditions, irrigation schedules should be reconsidered when water cost is high and/or water is scarce; in such cases, an irrigation schedule that includes water deficit at the vegetative development stage can be applied.

Chinese citrus fly is the major pest of sweet orange in citrus growing districts of Bagmati Province Nepal. Farmer’s production constrains and production problems such as Chinese citrus fly problem in sweet orange are not well documented and studied. This study was conducted in Sindhuli, Ramechhap, Dolakha and Kavre districts of Bagmati Province in 2021 with aim to understand the farmer’s perception, knowledge about CCF and their management practices using semi-structured questionnaire. Collected survey data was analyzed using the SPSS-20 and MS Excel. The survey results depicted that the intensity of Chinese citrus fly damage has been decreased in Sindhuli district with the infestation level of < 20% in sweet orange orchard. However, CCF population as well as their damage level was in increasing trend of > 50% in sweet orange orchard in Ramechhap, and > 80% in Dolakha and Kavre district. Chinese citrus fly loss has been recorded up to 25% in Mandarin orange in Dolakha and Kavre district. Maximum Chinese citrus fly loss was recorded in sweet orange orchard in October month. Farmers usefully managed the dropping fruits by collecting in plastic bags and burying in pits. Great fruit fly bait, has been used for the CCF management in three districts except in Kavre. Majority of farmers reported that chemical pesticides are less effective or sometime not-effective for this pest management. This study provides a preliminary information about sweet orange orchard management practices, general pest problems, Chinese citrus fly and future management strategy in survey districts.

The prevalence of Huanglongbing (HLB) in Florida has forced growers to search for new management strategies to optimize fruit yield in young orchards and enable earlier economic returns given the likelihood of HLB-induced yield reductions during later years. There has been considerable interest in modifying orchard architecture design and fertilizer and irrigation management practices as strategies for increasing profitability. Our objectives were to evaluate how different combinations of horticultural practices including tree density, fertilization methods, and irrigation systems affect growth, foliar nutrient content, fruit yield, and fruit quality of young ‘Valencia’ sweet orange [Citrus sinensis (L.) Osbeck] trees during the early years of production under HLB-endemic conditions. The study was conducted in Fort Pierce, FL, from 2014 to 2020 on a 1- to 7-year-old orchard and evaluated the following treatments: standard tree density (358 trees/ha) and controlled-release fertilizer with microsprinkler irrigation (STD_dry_MS), high tree density (955 trees/ha) with fertigation and microsprinkler irrigation (HDS_fert_MS), and high tree density with fertigation and double-line drip irrigation (HDS_fert_DD). Annual foliar nutrient concentrations were usually within or higher than the recommended ranges throughout the study, with a tendency for decreases in several nutrients over time regardless of treatment, suggesting all fertilization strategies adequately met the tree nutrient demand. During fruit-bearing years, canopy volume, on a per-tree basis, was higher under STD_dry_MS (6.2–7.2 m3) than HDS_fert_MS (4.3–5.3 m3) or HDS_fert_DD (4.9–5.9 m3); however, high tree density resulted in greater canopy volume on an area basis, which explained the 86% to 300% increase in fruit yield per ha that resulted in moving from standard to high tree density. Although fruit yields per ha were generally greatest under HDS_fert_MS and HDS_fert_DD, they were lower than the 10-year Florida state average (26.5 Mg·ha−1) for standard tree density orchards, possibly due to the HLB incidence and the rootstock chosen. Although tree growth parameters and foliar nutrient concentrations varied in response to treatments, management practices that included high tree density and fertigation irrespective of irrigation systems produced the highest fruit yields and highest yield of solids. Soluble solids content (SSC) and titratable acidity (TA) were lower, and the SSC-to-TA ratio was highest under STD_dry_MS in 2016–17, with no treatment effects on quality parameters detected in other years. Both drip and microsprinkler fertigation methods sufficiently met tree nutrient demand at high tree density, but additional research is needed to determine optimal fertilization rates and better rootstock cultivars in young high-density sweet orange orchards under HLB-endemic conditions in the Indian River Citrus District.

Understanding of orchard nutrition status can facilitate the proper management of orchards for higher fruit yield and quality. From 2011 to 2019, the nutrition status of orchards in Hunan Province, a major citrus-producing area in china, were assessed. A total of 361 soil samples, 378 leaf samples and 285 fruit samples of sweet oranges including navel orange (citrus sinensis l. Osbeck ‘newhall’) and common sweet orange (citrus sinensis l. Osbeck ‘bingtangcheng’), and mandarins including satsuma mandarin (citrus unshiu marc. ‘miyagawa’) and ponkan (citrus reticulata blanco ‘xinnu’) were collected. These samples were from112 sweet orange orchards and 140 mandarin orchards. Parameters of soil, leaf and fruit nutrition and fruit quality were analyzed based on these samples. The results revealed that soil acidification occurred in 79.0% of sweet orange orchards (ph 3.56 to 8.12) and 74.7% of mandarin orchards (ph 2.75 to 8.15). Soil organic matter (om) was abundant in both sweet orange orchards (21.3 g/kg on average) and mandarin orchards (19.77 g/kg on average). Nutrient analysis demonstrated deficiencies of nitrogen (n), potassium (k) and boron (b) in soils and leaves of sweet orange and mandarin orchards. Zinc (zn) was abundant in soils but deficient in leaves, suggesting a low zn utilization efficiency in these orchards. Besides, excessive iron (fe), magnesium (mn) and copper (cu) were found in sweet orange and mandarin leaves, which may be associated with low soil ph and fungicides application in this area. The average contents of n, phosphorus (p) and k in the fruit were about 0.80%, 0.11% and 0.51%, respectively, with a ratio close to 1:0.14:0.6. Multiple linear regression (mlr) analysis revealed that leaf npk and molybdenum (mo) significantly affect fruit fresh fruit weight (ffw) and total soluble solids (tss), and leaf p is closely correlated with fruit titratable acid (ta).

Productive performance of ‘Pera’ sweet orange grafted onto 37 rootstocks in tropical cohesive soils under rainfed condition

In areas of finite groundwater resources, the groundwater used for irrigation must be used as efficiently as possible. Yields and water use characteristics of longer-maturity corn (Zea mays L.; 118-d relative maturity), shorter-maturity corn (97-d relative maturity), and grain sorghum [Sorghum bicolor (L.) Moench] under full and limited irrigation were evaluated from 1993 to 1996. Mean yield of longer-maturity corn was 15 bu/acre greater than that of shorter-maturity corn and 50 bu/acre greater than that of grain sorghum. Longer-maturity corn used the greatest amount of water, 3.4 in, greater than shorter-maturity corn or grain sorghum. Average water use rates were similar among the three crops. Mean water use efficiency for longer-maturity corn was not different from that of shorter-maturity corn; mean water use efficiency of grain sorghum was 1.4 bu/acre per in, less. Mean yield of fully irrigated crops was 15 bu/acre greater than that for crops under limited irrigation (replacing 70% of crop evapotranspiration [ET]). Water use efficiency of crops under limited irrigation was 0.7 bu/acre per in, greater than under full irrigation, but full irrigation of corn was more profitable than limited irrigation. These yields, average water use rates, and water use efficiencies indicate no justification for choosing shorter- over longer-maturity corn.

Biomass estimation models, biomass storage and ecosystem carbon stock in sweet orange orchards: Implications for land use management

In Sao Paulo State (SPS), sweet orange (Citrus sinensis) trees with huanglongbing (HLB) symptoms are infected with Candidatus (Ca.) Liberibacter (L.) asiaticus (Las) or Ca. L. americanus (Lam). However, in 2007, 3 years after HLB was first reported in SPS, some trees with characteristic HLB symptoms were found free of liberibacters, but infected with a phytoplasma of 16Sr group IX. This phytoplasma was further characterized by PCR amplification of ribosomal protein genes rpsC-rplV-rpsS and amplicon sequencing. A qPCR test to detect the phytoplasma in plants and insects was also developed on the basis of the ribosomal protein genes. The phytoplasma was transmitted from citrus-to-citrus by grafting. The 16Sr group IX phytoplasma associated with HLB symptoms in sweet orange in SPS and characterized by the above techniques was named “HLB-phytoplasma”. Although the HLB-phytoplasma is widely distributed in many municipalities of central, northern, and northwestern SPS, the number of HLB-phytoplasma-infected trees in each municipality is very small. Experiments have been undertaken to identify the origin of the HLB-phytoplasma and the source of inoculum on which a putative insect vector could become infected with the HLB-phytoplasma. In SPS, sunn hemp (Crotalaria juncea L.) is a major, widely distributed cover crop. A 16Sr group IX phytoplasma was detected in sunn hemp plants with witches’ broom and virescence symptoms, and was shown to have 16Sr DNA sequences and ribosomal protein gene sequences with 100% identity to the corresponding sequences of the sweet orange HLB-phytoplasma. Transmission electron microscopy revealed the presence of phytoplasma cells in the phloem sieve tubes of infected C. juncea stalks. These results were taken as evidence that the sunn hemp phytoplasma and the sweet orange HLB-phytoplasma were identical. Scaphytopius marginelineatus, a leafhopper frequently found in sweet orange orchards, was shown to acquire the HLB-phytoplasma efficiently from affected sunn hemp plants, but acquisition from, and transmission rates to, sweet orange were very low. On the whole, these data suggest that (i) sunn hemp is a major source of inoculum of the HLB-phytoplasma, (ii) S. marginelineatus becomes infected on sunn hemp and transmits the phytoplasma to sweet orange, and (iii) transmission from sweet orange to sweet orange occurs only rarely, if at all. 16Sr group IX phytoplasmas, very closely related to the SPS HLB-phytoplasma, have also been detected in citrus in Minas Gerais and Bahia states (Brazil) and Mexico.

HighlightsIrrigated grain sorghum yield and irrigation water use decreased under climate change.Increase in growing season temperature beyond 26°C resulted in a sharp decline in grain sorghum yield.Irrigating during early reproductive stages resulted in the most efficient use of limited water.Irrigating to replenish soil water to 80% of field capacity was found suitable for both current and future climates. Groundwater overdraft from the Ogallala Aquifer for irrigation use and anticipated climate change impacts pose major threats to the sustainability of agriculture in the Texas High Plains (THP) region. In this study, the DSSAT-CSM-CERES-Sorghum model was used to simulate climate change impacts on grain sorghum production under full and deficit irrigation strategies and suggest optimal deficit irrigation strategies. Two irrigation strategies were designed based on (1) crop growth stage and (2) soil water deficit. For the first strategy, seven deficit irrigation scenarios and one full irrigation scenario were simulated: three scenarios with a single 100 mm irrigation scheduled between panicle initiation and boot (T1), between boot and early grain filling (T2), and between early and late grain filling (T3) growth stages; three 200 mm irrigation treatments with combinations of T1 and T2 (T4), T1 and T3 (T5), and T2 and T3 (T6); one 300 mm irrigation scenario (T7) that was a combination of T1, T2, and T3; and a full irrigation scenario (T8) in which irrigation was applied throughout the growing season to maintain at least 50% of plant-available water in the top 30 cm soil profile. For the second strategy, the irrigation schedule obtained from auto-irrigation (T8) was mimicked to create a full irrigation scenario (I100) and six deficit irrigation scenarios. In the deficit irrigation scenarios, water was applied on the same dates as scenario I100; however, the irrigation amounts of scenario I100 were reduced by 10%, 20%, 30%, 40%, 50%, and 60% to create deficit irrigation scenarios I90, I80, I70, I60, I50, and I40, respectively. Projected climate forcings were drawn from nine global climate models (GCMs) and two representative concentration pathways (RCP 4.5 and RCP 8.5). Climate change analysis indicated that grain sorghum yield under full irrigation was expected to be reduced by 5% by mid-century (2036 to 2065) and by 15% by late-century (2066 to 2095) under RCP 8.5 compared to the baseline period (1976 to 2005). Simulated future irrigation water demand of grain sorghum was reduced due to the shorter growing season and improved dry matter- and yield-transpiration productivity, likely due to CO2 fertilization. Based on the simulated grain sorghum yield and irrigation water use efficiency, the most efficient use of limited irrigation was achieved by applying irrigation during the early reproductive stages of grain sorghum (panicle initiation through early grain filling). A 20% deficit irrigation scenario was found to be optimal for current and future conditions because it was more water use efficient than full irrigation with a minor yield reduction of <11%. In summary, these results indicated that strategic planning of when and how much to irrigate could help in getting the most out of limited irrigation. Keywords: CERES-Sorghum, Critical growth stages, Crop yield, Global climate model, Irrigation demand, Soil water depletion.

This study aimed to investigate the profitability analysis of sweet orange production in Mamfe municipality, Cameroon. The study employed primary data collection through self-administered questionnaires to sweet orange farmers and a total of 200 samples were selected. The study used financial profitability analyses and percentage ranking to estimate the result. The gross return and net return for a hectare of the sweet orange orchard were 14155000 FCFA and 11759200 FCFA respectively for a 12 year sweet orange orchard. The NPV was estimated to be 4447824 FCFA per hectare of sweet orange orchard which indicates that sweet orange production fetches higher returns. The estimated BCR was 3.95 for a hectare of sweet orange orchard which shows that investment in sweet orange production is feasible for farmers. The production of sweet orange production was also found to be a profitable investment since the IRR was high (34.836%). The results also revealed that profits from sweet orange production have an impact on the livelihood of farmers. The result from the percentage ranking shows that the major constraints of sweet orange farmers are credit facilities, lack of agrochemicals, absence of extension services, high cost of farm inputs, high cost of labor, pests and diseases, and bushfires. The study concluded that sweet orange production was profitable and recommended that decision makers should promote sweet orange production via easy agricultural credits and others. This is a wise step towards improve well-being in Mamfe municipality in particular and Cameroon at large.

<abstract><title><italic>Abstract.</italic></title> With uncertainty in future irrigation water availability and regulations on nutrient application amounts, experimentally determined effects of “controllable” management strategies such as nitrogen (N), water, and their combination on crop water productivity (CWP, also known as crop water use efficiency) and actual evapotranspiration (ET_a) are essential. The effects of various N application rates (0, 84, 140, 196, and 252 kg ha^-1) under fully irrigated (FIT), limited irrigation (75% FIT), and rainfed conditions on maize (Zea mays L.) yield and various CWP indices were investigated in 2011 and 2012 growing seasons under linear-move sprinkler irrigation in south central Nebraska. CWP was presented as crop water use efficiency (CWUE), irrigation water use efficiency (IWUE), and evapotranspiration water use efficiency (ETWUE). The seasonal rainfall amounts in 2011 and 2012 were 371 mm and 296 mm, respectively, as compared with the long-term average of 469 mm. Two experimental seasons were contrasted with extreme warmer temperatures, greater solar radiation, and lower rainfall in 2012. Maximum grain yield of 12.68 metric tons ha^-1 and 14.42 tons ha^-1 was observed in 2011 and 2012, respectively, under the fully irrigated and 252 kg N ha^-1 treatment. Grain yield was linearly related to ET_a and curvilinearly related to N and irrigation application amounts. Lower N treatments were more susceptible to interannual effects on the grain yield response to irrigation water amount. CWUE ranged from 1.52 kg m^-3 (FIT and 84 kg N ha^-1) to 2.58 kg m^-3 (rainfed and 196 kg N ha^-1) with an average of 2.15 kg m^-3 in 2011, and from 1.49 kg m^-3 (FIT and 0 kg N ha^-1) to 2.72 kg m^-3 (rainfed and 252 kg N ha^-1) with an average of 2.33 kg m^-3 in 2012. CWUE had a positive quadratic relationship with N application amount and decreased with both the presence and amount of irrigation at a given N application amount. The maximum IWUE for 75% FIT and FIT in 2011 was 1.80 kg m^-3 (252 kg N ha^-1) and 1.51 kg m^-3 (252 kg N ha^-1), respectively, whereas in 2012 the maximum IWUE values were 1.40 kg m^-3 (196 kg N ha^-1) and 1.78 kg m^-3 (252 kg N ha^-1), respectively. A curvilinear relationship was observed between IWUE and N application amount. An optimal N application amount of 196 kg ha^-1 was identified for the pooled data to maximize the increase in grain yield above rainfed conditions per unit of applied irrigation water under limited irrigation management practices. In 2011, ETWUE ranged from 0.22 kg m^-3 (140 kg N ha^-1) to 1.46 kg m^-3 (196 kg N ha^-1) and from -0.21 kg m^-3 (84 kg N ha^-1) to 3.74 kg m^-3 (252 kg N ha^-1) for 75% FIT and FIT, respectively, whereas in 2012 ETWUE ranged from -0.07 kg m^-3 (0 kg N ha^-1) to 1.87 kg m^-3 (252 kg N ha^-1) and from -0.14 kg m^-3 (0 kg N ha^-1) to 3.65 kg m^-3 (196 kg N ha^-1) for 75% FIT and FIT, respectively. The results support that there is an optimal N level for each irrigation regime and, in general, lower N application amounts are required to reach maximum productivity (e.g., CWUE) under limited and rainfed conditions as compared with the FIT. In other words, there is an optimal N application amount to maximize the effectiveness of irrigation water on increasing grain yield above rainfed yields. The optimal N level for maximum productivity varied not only between the irrigation levels, but also exhibited interannual variability for the same irrigation level, indicating that these variables are impacted by the climatic conditions.

Countries such as Egypt, which are situated in semi‐arid regions and have water constraints, primarily aim to repurpose unconventional water resources for irrigation. The aim of this research was to examine the feasibility and advantages of irrigating barley with fish farm drainage water (DWFF) rather than fresh irrigation water (IW). Four degrees of deficit irrigation [100% FI (full irrigation), 80% FI, 60% FI and 40% FI] were studied for the irrigation of barley via two types of water (DWFF and IW). The response of crops to a deficit irrigation approach involving the use of IW in the two seasons of 2020–2021 and 2021–2022 was demonstrated by the results. The yield of the barley produced with DWFF irrigation was greater than that produced with IW irrigation, ranging from 9% to 12% in 2020–2021 and from 9% to 13% in 2021–2022. This resulted from the higher concentration of dissolved biological nitrogen and other nutrients in DWFFs. There was a strong correlation between the observed and simulated crop yield values for both growing seasons, with R2 values of 0.963 and 0.960, respectively, for all the treatments. The SALTMED model was used to simulate the soil moisture content, water application efficiency, barley dry matter, yield and water productivity for all the treatments. The study concluded that DWFF is a useful irrigation substitute for IW. Higher yields were also attained with the use of less IW and chemical fertilisers because of the DWFF. In addition, there are other advantages, such as increasing farmer income and lowering discharge to the drainage network.

Citrus black spot (CBS) may cause substantial yield loss in sweet orange orchards. Severity and distribution of CBS symptoms on fruit may be variable and not all affected fruit may fall. However, the relationship between CBS symptoms and yield loss has not yet been investigated. This study aimed to determine CBS characteristics associated with premature fruit drop. A set of fruit was removed from the tree to measure the detachment force and another set of dropped fruit was collected from Pera and Valencia sweet orange orchards in three municipalities in Sao Paulo state, Brazil. CBS severity, distance of the nearest lesion from the peduncle, and fruit peel colour were assessed in both fruit sets. CBS severity was consistently related with the force to remove fruit and hence associated to the premature fruit drop, irrespective of the cultivar and location. The segmented linear regression showed that the fruit detachment force was reduced abruptly, at a rate of 7% for every 1% increase in disease severity up to 4.2 ± 1.0% CBS severity and, above this breakpoint, the force decreased slightly at a rate of 1.5%. Taking into account all orchards, the proportion of dropped fruit with CBS severity higher than the breakpoint was approximately 90%. This study provides a better understanding of the relationship between CBS severity and premature fruit drop of sweet orange. CBS severity breakpoint may be used as a reference to anticipate harvest and reduce CBS‐related yield loss in orchards intended for juice processing.