Leaf area is an important parameter in agronomic and physiological studies; thereby, the techniques used for its determination should be simple, fast and accurate. The objective of this study was to evaluate the efficiency of an equation for the indirect determination of leaf area in 'Conilon' (Coffea canephora) genotypes cultivated in the Western Amazon. The experiment was carried out in Porto Velho, Rondônia, in August and September 2011. It was arranged in a completely randomized 2 × 15 factorial design combining two methods of determining leaf area (estimated and actual) and fifteen 'Conilon' coffee genotypes, with 64replicates. The estimated leaf area was determined by the equation LA = 0.3064 × Age -0.0556 × LMR -2.0133 (R 2 =0.98), developed by Partelli et al. (2006), while the actual leaf area was obtained from images of leaves scanned into digital format using an image scanner. The genotypes belong to the Coffee Breeding Program at Embrapa Rondônia. The efficiency of the equation for determining leaf area of 'Conilon' coffee varies according to the genotype evaluated; therefore, the equation must not be used without prior calibration. As the species is a perennial crop and the number of commercial genotypes widely accepted by farmers is restricted, the validation of the equation or the development of new equations capable of estimating the leaf area of the cultivated genotypes can help in the management of coffee plantationsn.

The objective of this work was to evaluate urease inhibitors for the reduction of ammonia volatilization in Amazonian soils. The work was carried out on a clayey yellow Oxisol, a clayey red Oxisol, and on a light silty Ultisol. Each experiment was conducted in split plots, using standard urea, urea + a benzimidazole-type urease inhibitor (BZI1), urea + a benzoylthiourea-type urease inhibitor (RTB68), urea + N-(n-butyl) triamide thiophosphate (NBPT), or a fertilizer-free control. Volatilized ammonia was collected at 48, 96, 144, 192, 240, 288, 336, and 384 hours after fertilization. Ammonia volatilization reached a maximum at 144 hours in the urea, urea + benzimidazole, and urea + benzoylthiourea treatments. A peak level was reached at 192 and 288 hours in the urea + N-(n-butyl) triamide thiophosphate treatment. In yellow Oxisols, benzimidazole and benzoylthiourea reduced the ammonia losses by 22 and 10%, respectively, in soils without urease inhibitors. However, neither of these agents significantly reduced ammonia volatilization at the rate determined for standard urea in red Oxisols or Ultisols. N-(n-butyl) triamide thiophosphate is the most efficient urease inhibitor for the soils of southwestern Amazonia.

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This study presents an evaluation of the viability of using protected urea under different irrigation depths to reduce nitrogen losses caused by the volatilization of ammonia (NH3) under the conditions of the Southwestern Amazon. The study was carried out at the Experimental Station of Embrapa Rondônia, in the municipality of Porto Velho, Rondônia State, Brazil. The experiment was conducted in a Red-Yellow Latosol and arranged in a 5 x 6 factorial design consisting of a combination of five treatments (N sources) with six irrigation depths. The sources of N were as follows: 1) urea (45.5% N); 2) urea (44.3% N) + 0.15% copper and 0.4% boron; 3) urea (45% N) + NBPT; 4) urea (43% N) + sulfur (1%); and 5) control (without N). The irrigation depths were 0, 5, 10, 15, 20, and 25 mm. The results showed that, regardless of the use of urease inhibitors, an irrigation depth of 10 mm is suitable for incorporating urea into the soil and stabilizing N losses from NH3 volatilization. NBPT is the most efficient inhibitor under nonirrigated conditions. All N sources promote increases in the concentrations of nitric and ammonia nitrogen in the soil. In the first 15 days after fertilizer application, the highest concentrations of ammonium were in the 0 - 10 cm and 10 - 20 cm soil layers, and NBPT showed the highest ammonium content compared to that of the other sources in the 0 - 10 cm layer. The nitric nitrogen content in the soil was slightly influenced by the irrigation depth in the first 15 days after fertilizer application. However, the ammonia nitrogen content decreased exponentially with the increase in irrigation depth due to the movement of ammonia in the soil.

In Coffea canephora, the number of orthotropic shoots is directly related to plant yield. The objective of this study was to evaluate the vegetative and yield performance of Coffea canephora, from the botanical variety Conilon, under different management systems for early emission of orthotropic shoots. The experiment was carried out in Ouro Preto do Oeste, Rondônia, between November 2011 and May 2014. Three types of management techniques were tested for early induction of orthotropic shoots in coffee trees (T1 = bending of the orthotropic shoot; T2 = apical pruning of the orthotropic shoot, T3 = free growing). The experiment was conducted in a randomized block design with 20 replicates. Each block consisted of a clonal genotype (clone) from the Embrapa Coffee Breeding Program. The techniques pruning and apical pruning were efficient to induce early growth of orthotropic shoots in Coffea canephora, resulting in higher yield in the first commercial bean production.

Knowledge of the expression of traits associated with drought tolerance is important to mitigate impacts on coffee production in a climate change scenario. This study aimed to understand the genetic divergence between Coffea canephora genotypes grown in the Western Amazon based on leaf vegetative and anatomical traits. For this, fifteen high-performance genotypes were evaluated in a randomized block design with five replications of one plant per plot to analyze three leaf vegetative traits (leaf area index, root volume, and total dry mass) and five leaf anatomical traits (polar and equatorial diameter, density and number of stomata, and stomatal area). The data were interpreted using analysis of variance and the Scott-Knott mean cluster test (p ≤ 0.05). The Tocher optimization method and principal component analysis with reference points were used to quantify the genetic divergence. Tocher clustering separated the fifteen clones into five groups, and the scatter in the plane into three groups. Stomatal density was the trait that most contributed to the dissimilarity between genotypes with the potential to be used in future studies for the selection of water deficit-tolerant genotypes. The BRS 3213 genotype showed the greatest genetic dissimilarity and composed a group isolated from the other genotypes in terms of anatomical characteristics. Hybrids 12 and 15 have leaf anatomical traits with higher drought tolerance potential.

The nutritional management of the coffee clonal garden influences the production and physiological quality and seedlings production of vegetative propagules. Thus, this study aimed to analyze the seedlings’ production from clonal cuttings taken from Coffea canephora mother plants grown with increasing nitrogen mineral doses. The cuttings were taken from C. canephora var. botany Robusta, from the Embrapa Genetic Improvement Program of Rondônia. The mother plants received nitrogen fertilizer at different doses: 0 (Control); 50; 100; 150; 200; 250 and 300 kg of N per hectare divided into 4 applications, during 150 days of orthotropic stems growth (shoots). The following parameters were evaluated: Dry mass of cuttings, nutritional content of cuttings, and seedlings production, with growth analysis at 0, 48, 61, 80, 101, 122, 143, and 164 days after staking (DAS) and analysis of vegetative characteristics at 122 DAS. The nitrogen fertilization in the mother plant resulted in the variation of macronutrient accumulation in cuttings, but the order K> N> Ca> P> Mg> S was maintained, regardless of N dose. In addition, a positive correlation between nitrogen doses and dry matter accumulation, as well as the physiological quality of seedlings was identified.

Little is known about the management of high-yield clonal Coffea canephora in the Amazonian Region, mainly for nutritional aspects and cultivation system efficiency. This study aimed to evaluate the influence of different nitrogen and potassium fertilization rates on coffee grain yield and fertilizer use efficiency of C. canephora trees. An experiment was performed at an experimental field of the Embrapa Rondônia in Porto Velho (RO), Brazil. It was carried out in a split-plot scheme with six doses of 20-00-20 NPK formulation (0; 250; 500; 1,000; 2,000; and 3,000 kg ha-1) and three years of evaluation (2014, 2015, and 2016). An interaction between fertilizer dose and crop year was observed. Fertilizer doses showed an exponential behavior, with maximum yields of 51, 114, and 79 bags ha-1 at 3,000 kg ha-1 in the crop years of 2014, 2015, and 2016, respectively. Such a behavior impacted average and accumulated yields in the three harvest seasons. As for crop year effect within each fertilizer dose, the highest yield was reached in the second harvest after pruning for renewal of orthotropic stems. Moreover, fertilizer use efficiency by plants decreased exponentially, with the highest value at the lowest dose. Increasing doses of 20-00-20 formulation promoted an exponential increase in grain yield but decreased its use efficiency by C. canephora plants. This management also stimulated a strong biannual production.