We evaluated the effect of phosphorus application rates from various sources and in the presence or absence of filter cake on soil phosphorus, plant phosphorus, changes in acid phosphatase activity, and sugarcane productivity grown in Eutrophic Red Ultisol. Three P sources were used (triple superphosphate, Araxa rock phosphate, and Bayovar rock phosphate) and four application rates (0, 90, 180, and 360 kg ha−1 of P2O5) in the presence or absence of filter cake (7.5 t ha−1, dry basis). The soil P, the accumulated plant P, the leaf acid phosphatase activity and straw, the stalk productivity, the concentration of soluble solids in the juice (Brix), the juice sucrose content (Pol), and the purity were the parameters evaluated. We found that P applications increased levels of soil, leaf, and juice phosphorus and led to higher phosphorus accumulation and greater stalk and straw productivity. These levels were highest in the presence of filter cake. Acid phosphatase activity decreased with increasing plant phosphorus concentration. Phosphate fertilization did not show effect on sugarcane technological quality. We concluded that P application, regardless of source, improved phosphorus nutrition and increased productivity in sugarcane and, when associated with filter cake, reduced the need for mineral fertilizer.
Morphoagronomic characteristics of maize in response to different levels of defoliationThe present study was conducted to evaluate the damage caused by defoliation in maize. The experiment was carried out in 2005/2006 at Roma Farm, Ituverava-SP, using the triple hybrid CODETEC 304®. The experiment consisted of split plots (split-plot), which were distributed at random in three blocks, with the main treatment manual defoliation (30%, 40%, 60% and 80% defoliation) in the plots and as the secondary treatment the phenological phases (D1, D2 and D3) with three replicates for each treatment and a control plot (0% defoliation) for each block. It was evaluated the production of plots (g/m 2 ), the average size of the spikes (cm) and the average weight of thousand grains (g). According to the results, it was concluded that the source-sink relations were negatively affected, and the treatment with 80% defoliation was the one that most affected all variables, thus, it is a level of defoliation that is responsible for the largest losses, with no means of compensation for the maize crop.
Biological damage caused by macronutrient deficiency in watermelon plants is still not known, and may lead to nutritional disorders and alterations in absorption and utilization efficiencies, depending on the evaluated nutrient. In this context, the aim of the present study was to evaluate the growth and nutritional efficiency of watermelon plants grown under macronutrient deficiencies. The experiments were carried out in pots containing an aerated nutrient solution. Treatments consisted of the nutrient solution containing (control) or lacking nitrogen (LN), phosphorus (LP), potassium (LK), calcium (LCa), magnesium (LMg), and sulfur (LS), in a completely randomized design with three replications. At the end of the experiment with the onset of symptoms of deficiency, plant growth, green color index, nutrient accumulation, nutrient uptake, nutrient utilization efficiency, root density, and foliar deficiency symptoms were evaluated. P, K, Ca, Mg, and S deficiencies increased plant utilization efficiency and can potentiate watermelon development in environments deficient in these nutrients. The opposite was observed concerning nitrogen deficiency, because this condition induced greater biological damage, with low utilization efficiency, indicating the sensitivity of this species in low N conditions.
Sugarcane filter cake, a phosphorus-rich (P) fertilizer, can affect not only P storage in sugarcane (Saccharum officinarum L.), but also its metabolism and photosynthesis. In this study, was evaluated the effect of different mineral fertilizers, with and without the use of filter cake, on P levels, gas exchange, acid phosphatase activity, sugar, hydrated alcohol production, and total soluble solids. Sugarcane (variety RB86 7515) was cultivated on dystrophic Typic Haplustox in a randomized complete block design. Three replicates were established in a 3 × 4 × 2 factorial scheme, with three P sources (Triple Superphosphate-TS, Natural Reactive Bayovar Phosphate-BP, and Natural Araxa Phosphate-AP), four rates of P as P 2 O 5 (0, 90, 180, and 360 kg ha −1), and the presence or absence of filter cake (7.5 Mg ha −1 , dry weight). The levels of foliar P (PCL) were determined, along with the accumulation of P in aerial plant parts (AAP), net CO 2 assimilation (A), stomatal conductance (g s), transpiration rate (E), acid phosphatase activity (APL), hydrated alcohol, total soluble solids (TSS), total recoverable sugar (TRS), and stalk production. The highest P rate with filter cake yielded the maximum concentration of P in leaves (1.7 g kg −1), leading to the highest P accumulation in aerial plant parts (17.8 kg ha −1), and furthering a sugar production of 197.1 kg t −1 , and stalk production (122.6 Mg ha −1). The highest rate of Triple Superphosphate alone or with filter cake yielded the lowest acid phosphatase activity, the highest rate increased the accumulation of P in aerial parts (18.8 kg ha −1), and for stalk production, produced 123.1 Mg ha −1 of stalks. The use of Triple Superphosphate associated with filter cake increased the production of sugar (192.5 kg t −1), hydrated alcohol (91.3 L t −1) and total soluble solids (18.4°Brix), while the use of higher P rates, regardless of the source, increased gaseous exchange in sugarcane plants.
Increases in production and final quality of the sugarcane crop require the search for new management and evaluation techniques within the production system, which can range from water and nutritional management, such as the application of water saving irrigation associated with sources (conventional and alternative) and phosphorus doses combined with the use of a sophisticated mathematical method, such as multivariate analysis. It can explain the variations caused by the application of irrigation and the sources and doses of phosphorus throughout the crop cycle. Due to the complex relationships and interactions of the soil-waterplant-atmosphere system, the use of multivariate analysis is able to indicate the best management options to be used. The experiment was carried out in a dystrophic Red Yellow Latosol, medium texture. The experiment consisted of randomized blocks and three replications in a 3 × 4 × 2 factorial design comprising three sources of phosphorus (triple superphosphate, Bayóvar natural reactive phosphate, and Araxá natural phosphate) and different doses (0, 90, 180, and 360 kg of P 2 O 5 ha −1) in the presence and absence of filter cake (7.5 Mg ha −1 , dry basis). Irrigation with rescue equipment was applied in a single blade of 80 mm. Biometrics, nutritional status, and agroindustrial performance of sugarcane were evaluated. The principal component analysis evidenced that the phosphate fertilization associated with filter cake is responsible for increases in sugarcane biometrics, specially tillers at 6 months (0.589) and final tillering (0.577); nutritional status of iron (0.349), manganese (0.348), boron (0.347), sulfur (0.332), and phosphorus (0.331); and agroindustrial performance of sucrose (0.476), stalk yield (0.470), and total recoverable sugar (0.439). The water saving irrigation potentiated the use of phosphate fertilizer associated with filter cake, increasing the nutritional status of the plants. However, the correlation was irrelevant and or negative for levels of potassium and calcium. In addition, it favored biometrics and agroindustrial performance by expressing a direct and positive correlation with stalk yield, sucrose, and total recoverable sugar, but an inverse correlation between final tillering and plant height, tons of pol per hectare, and total recoverable sugar.
La medición indirecta de la clorofila es un método de diagnóstico del nitrógeno en plantas y su precisión puede ser influenciada por la hora en que se hace la lectura, por la posición del foliolo en la planta y porción donde se realiza la lectura en el foliolo. El objetivo fue evaluar el efecto del horario de lectura, la posición terminal del foliolo en las hojas y la porción del foliolo en la estimación indirecta del Índice de contenido de clorofila (ICC) con el uso del clorofilómetro. El experimento se realizó con el cultivo de papa (S. tuberosum L.), variedad Ágata, en el municipio de Ituverava, estado de São Paulo, Brasil y constó de 27 tratamientos, en un esquema factorial 3 x 3 x 3 con cuatro repeticiones de 16 plantas cada una, con una distribución aleatoria. Los tratamientos fueron: tres horarios de evaluación (08:00 am, 12:00 pm y 16:00 pm), tres posiciones de foliolos en las hojas (tercera, cuarta y quinta) y tres porciones del foliolo (basal, medio y distal). La evaluación del ICC en las hojas de las plantas de papa debe realizarse en los foliolos de la tercera y cuarta hoja, independientemente de las áreas foliares utilizadas, en el horario de las 08:00 am y a los 60 días después de plantado el cultivo. La cuantificación indirecta de la clorofila representa una herramienta fiable y con potencial para guiar el manejo de fertilizante nitrogenado para el cultivo.
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