Dirceu Mattos

Fruit yield of Valencia sweet orange fertilized with different N sources and the loss of applied N

Nutrient management recommendations are needed to increase nitrogen uptake efficiency, minimize nutrient losses and reduce adverse effects on the environment. A study of the effects of nitrogen fertilization on N losses and fruit yield of 6-yr-old Valencia sweet orange (Citrus sinensis (L.) Osb.) on Rangpur lime rootstock (C. limonia Osb.) grove was conducted in an Alfisol in Brazil from 1996 to 2001. Urea (UR) or ammonium nitrate (AN) fertilizers were surface-applied annually at rates of 20, 100, 180, and 260 kg N ha−1 split into three applications from mid-spring to early fall. A semi-open trapping system, using H3PO4 + glycerol-soaked plastic foams, was used for selected treatments in the field to evaluate NH3 volatilized from applied N fertilizers. Ammonia volatilization reached 26 to 44% of the N applied as UR at the highest rate of N used. Ammonia volatilization losses with AN were lower (4% of the N applied). On the other hand, AN resulted in greater nitrate leaching and greater soil acidification than UR. A marked effect of AN fertilizer on soil pH (CaCl2) in the 0–20 cm depth layer was observed with a decrease of up to 1.7 pH units at the highest N rate. Acidification was followed by a decrease in exchangeable Ca and Mg; consequently, after 5 yr of fertilization with AN, soil base saturation dropped from 77% in the plots treated with 20 kg N ha−1 per year, to 24% in those that received 260 kg N ha−1 per year. The effect of N sources on fruit yield varied from year to year. In 2001, for a calculated N application rate of 150 kg ha−1, the fertilizer efficiency index of UR was 75% of that of AN.

Nutrient content of biomass components of Hamlin sweet orange trees

ABSTRACT: The knowledge of the nutrient distribution in trees is important to establish sound nutrientmanagement programs for citrus production. Six-year-old Hamlin orange trees [ Citrus sinensis (L.) Osb.] onSwingle citrumelo [ Poncirus trifoliata (L.) Raf. x Citrus paradisi Macfad.] rootstock, grown on a sandy Entisolin Florida were harvested to investigate the macro and micronutrient distributions of biomass components.The biomass of aboveground components of the tree represented the largest proportion of the total. Thedistribution of the total tree dry weight was: fruit = 30.3%, leaf = 9.7%, twig = 26.1%, trunk = 6.3%, and root =27.8%. Nutrient concentrations of recent mature leaves were in the adequate to optimal range as suggestedby interpretation of leaf analysis in Florida. Concentrations of Ca in older leaves and woody tissues weremuch greater than those in the other parts of the tree. Concentrations of micronutrients were markedly greaterin fibrous root as compared to woody roots. Calcium made up the greatest amount of nutrient in the citrus tree(273.8 g per tree), followed by N and K (234.7 and 181.5€g€per€tree, respectively). Other macronutrientscomprised about 11% of the total nutrient content of trees . The contents of various nutrients in fruits were: N= 1.20, K = 1.54, P = 0.18, Ca = 0.57, Mg = 0.12, S = 0.09, B = 1.63€x€10

Nitrogen and Irrigation Management Practices to Improve Nitrogen Uptake Efficiency and Minimize Leaching Losses

Summary Nitrogen (N) is the most important nutrient for plant growth and production. Nitrogen uptake efficiency is dependent on a number of factors. Water management influences the transformation of N sources applied to the soil and transport of the nitrate form of N in the soil. Nitrate-N is the final product of N transformations and is quite mobile in soils with the water front. Leaching of nitrate below the rootzone is an economic loss and contributes to non-point source pollution of groundwater. In this chapter we summarize the factors influencing the N uptake efficiencies for various crops and production systems, and chemical and biological processes that influence the N transformation or losses. Recent advances leading to development of N and irrigation best management practices that support sustainable crop production and net returns while minimizing the non-point source nitrate pollution of ground-water are also discussed.

Potassium Management for Optimizing Citrus Production and Quality

Abstract Potassium (K) is highly mobile in plants at all levels, that is, from individual cell to xylem and phloem transport. This cation plays a major role in (1) enzyme activation; (2) protein synthesis; (3) stomatal function; (4) stabilization of internal pH; (5) photosynthesis; (6) turgorrelated processes; and (7) transport of metabolites. Citrus trees generally do not show visible deficiency symptoms across a wide range of K status in the leaves, except when the leaf concentrations drop below 3-4 mg kg21. However, fruit quality is quite sensitive to varying levels of K availability. High levels of K cause large fruit size with thick and coarse peel. In contrast, K deficiency produces smaller fruits with thin peel. With regard to juice properties, K nutrition has a significant role in juice acidity; that is, high juice acidity with high K availability, while low K availability causes decrease in juice acidity. High K availability in the soil can reduce the uptake of other cations, primarily magnesium, calcium, and ammonium N. In this paper, the available information on the effects of varying availability of K on the fruit yield, postharvest quality of fruit, as well as juice quality is summarized. The current recommendations on the application of soil and leaf analysis for evaluation of the K nutritional status and guidelines for K fertilization are also discussed.

Response of Young Citrus Trees on Selected Rootstocks to Nitrogen, Phosphorus, and Potassium Fertilization

ABSTRACT The majority of the citriculture in Brazil is located in the state of São Paulo, with a total production area of 700,000 ha. Trees are grafted mostly on ‘Rangpur’ lime (RL; Citrus limonia Osbeck) rootstock. Despite its good horticultural performance, use of other rootstocks has increased with the search for disease-tolerant varieties to improve grove productivity and longevity. Furthermore, there is a lack of information on young tree response to fertilization, and optimal nutrient requirements of different scion/rootstock combinations for maximum fruit yield. A network of field experiments was conducted to study the differential response of young sweet orange trees on selected rootstocks to nitrogen (N), phosphorus (P), and potassium (K) fertilization. The application of soil and leaf analyses to develop optimal fertilizer recommendations was evaluated. Experiments were conducted in three locations using fractional factorial design of one-half (4 × 4 × 4) type with four rates of N, P, or K calculated to be applied for five years after tree planting. Fruit yield response was evaluated during the last two years and correlated with soil and leaf analyses data. The trees on RL rootstock demonstrated increased efficiency of nutrient use and fruit production compared with those on ‘Cleopatra’ mandarin (CL; C. reshni hort. ex Tanaka) or ‘Swingle’ citrumelo [SW; Poncirus trifoliata (L.) Raf. × C. × paradisi Macfad.] rootstocks. The trees on SW rootstock appeared to require greater N and K rates than those on RL rootstock. Phosphorus requirement was greater for ‘Natal’ or ‘Valencia’ trees on CL than on RL rootstock. These results will become the basis for revising current fertilizer recommendation guidelines for young trees in Brazil.

Nitrogen Volatilization And Mineralization In A Sandy Entisol Of Florida Under Citrus

Increasingly nitrate nitrogen (NO3-N) is found in excess of maximum contaminant limit (MCL) in groundwater adjacent to citrus production areas of central Florida. Understanding of fate of N in the environment following the application of fertilizers is critical to improve nutrient uptake efficiency, minimize nutrient losses and reduce the adverse effects on the groundwater. A study evaluated ammonia volatilization (NH3) and effects of ammonium nitrate (AN) and urea (UR) on N budget of citrus trees on a sandy Entisol. Dry granular N fertilizers were surface applied to irrigated ‘Hamlin’ orange trees. Ammonia volatilization was evaluated using a semi-open NH3 trapping system with and without additional air circulation, while net N mineralization and leaching losses were evaluated using in situ incubations with polyvinyl chloride (PVC) columns. Significant N losses by NH3 volatilization were observed from applied N fertilizers, which accounted for up to 13% of applied N as AN, and 33% as UR with additional air circulation in the collection chamber. These values were significantly greater than those observed with no additional air circulation. Maximum rates of NH3 volatilization occurred within 5 d after fertilizer application and were greater during the day than during the evening. This study demonstrated that fertilizer use efficiency is reduced due to increased gaseous losses of NH3 when urea is used, and that N fertilization affects soil N mineralization in a short time period after fertilizer application. Fertilization decreased N mineralization and increased the amount of soil microbial biomass N during incubation. Leaching of N accounted to 13% of applied N during a 90-d period. #This research was supported by the Florida Agricultural Experiment Station and approved for publication as Journal Series no. R-08456.

Contribution of phosphorus ( 32 P) absorption and remobilization for citrus growth

Background and aimsPhosphorus (P) is a mobile nutrient in the plant so growth depends on its internal remobilization and a plant’s ability to respond to its availability in the growing media. This study was conducted to evaluate the influence of P status and rootstocks on the patterns of P uptake and remobilization in orange trees.MethodsSweet orange trees on Cleopatra mandarin (CM) or Rangpur lime (RL) rootstocks were grown for nine months in nutrient solution (NS) that was either P-deficient (DNS) or was P-sufficient (SNS). After this period, half of the trees were reciprocally transferred between DNS and SNS (from D to S and S to D), while the others remained in their initial P availability.ResultsTrees on RL had more shoot and root growth, accumulated more P and had greater efficiency of P absorption and transport to the shoot (PAE) than those on CM. The major source of P for growth was previously stored P even with an adequate current P supply to the roots. This suggested the dominance of P remobilization over P uptake and the requirement that trees had sufficient stored P to meet P demand of new growth. Trees on CM had greater concentrations of remobilized P in new shoots than trees on RL.ConclusionTrees grafted on rootstocks less able to take up P (CM) were more dependent on the internal reserves of P for new growth than rootstocks with higher PAE (RL).

BORON UPTAKE AND DISTRIBUTION IN FIELD GROWN CITRUS TREES

In low fertility tropical soils, boron (B) deficiency impairs fruit production. However, little information is available on the efficiency of nutrient application and use by trees. Therefore, this work verified the effects of soil and foliar applications of boron in a commercial citrus orchard. An experiment was conducted with fertigated 4-year-old ‘Valencia’ sweet orange trees on ‘Swingle’ citrumelo rootstock. Boron (isotopically-enriched 10B) was supplied to trees once or twice in the growing season, either dripped in the soil or sprayed on the leaves. Trees were sampled at different periods and separated into different parts for total B contents and 10B/11B isotope ratios analyses. Soil B applied via fertigation was more efficient than foliar application for the organs grown after the B fertilization. Recovery of labeled B by fruits was 21% for fertigation and 7% for foliar application. Residual effects of nutrient application in the grove were observed in the year after labeled fertilizer application, which greater proportions derived from the soil supply.

Advances in Nitrogen Fertigation of Citrus

ABSTRACT Advances in micro-irrigation techniques, i.e., drip and under-the-tree sprinklers, have facilitated greater adoption of fertigation especially for perennial crops including citrus (Citrus sinensis). Fertigation can improve nutrient uptake efficiency and minimize leaching of nutrients below the root zone, and thus can contribute to an increase in crop yield as well as crop quality as compared to those with conventional dry fertilizer broadcast application. In this paper, we summarized the recent fertigation studies on citrus. Long-term studies (over five to six years) have demonstrated that fertigation was beneficial as compared with broadcast of dry granular fertilizer for: (i) increased tree canopy area of young trees; (ii) increased fruit as well as juice yield of bearing orange and grapefruit (Citrus paradisi) trees; and (iii) decreased NO3-N concentration in surficial aquifer. Citrus groves with drip or under-the-tree microsprinkler irrigation are ideal for fertigation with minimal or no extra cost for application of fertilizers. Soil area wetted by the sprinklers or drip emitters must be considered for success of fertigation. Fertigation must be avoided during heavy rainfall period to minimize leaching of nutrients and water below the rootzone.

Uptake and distribution of soil applied zinc by citrus trees-addressing fertilizer use efficiency with 68Zn labeling.

The zinc (Zn) supply increases the fruit yield of Citrus trees that are grown, especially in the highly weathered soils of the tropics due to the inherently low nutrient availability in the soil solution. Leaf sprays containing micronutrients are commonly applied to orchards, even though the nutrient supply via soil could be of practical value. This study aimed to evaluate the effect of Zn fertilizers that are applied to the soil surface on absorption and partitioning of the nutrient by citrus trees. A greenhouse experiment was conducted with one-year-old sweet orange trees. The plants were grown in soils with different textures (18.1 or 64.4% clay) that received 1.8 g Zn per plant, in the form of either ZnO or ZnSO4 enriched with the stable isotope 68Zn. Zinc fertilization increased the availability of the nutrient in the soil and the content in the orange trees. Greater responses were obtained when ZnSO4 was applied to the sandy loam soil due to its lower specific metal adsorption compared to that of the clay soil. The trunk and branches accumulated the most fertilizer-derived Zn (Zndff) and thus represent the major reserve organ for this nutrient in the plant. The trees recovered up to 4% of the applied Zndff. Despite this relative low recovery, the Zn requirement of the trees was met with the selected treatment based on the total leaf nutrient content and increased Cu/Zn-SOD activity in the leaves. We conclude that the efficiency of Zn fertilizers depends on the fertilizer source and the soil texture, which must be taken into account by guidelines for fruit crop fertilization via soil, in substitution or complementation of traditional foliar sprays.