Productivity and Dry Matter Accumulation of Sugarcane Crop under Irrigation and Nitrogen Application at Rio Verde GO, Brazil

Dry matter production and productivity of stem currently are being widely studied in sugarcane, reinforcing the study in question, which aims to assess the accumulation of dry matter of the aerial segment and the productivity of stems of sugarcane crops within the first cycle, at different levels of water replacement (WR) with and without nitrogen fertilization, through a subsurface drip irrigation system. The assay was conducted in the experimental area of the Federal Institut Goiano, Campus Rio Verde, GO, Brazil, in a dystroferric Rhodic Hapludox soil, cerrado phase (savannah), and comprised experimental splits of three furrows with an 8-meter long double row. Experimental design consisted of randomized blocks in a 5 × 2 factorial array, with four replications. Evaluated factors comprised five levels of WR (100%, 75%, 50%, 25% and 0% of field capacity), with and without the application of nitrogen (0 and 100 kg·ha-1 urea). Harvest occurred in May 2013 and stem productivity (SP), productivity of pointers (PP), productivity of straw (PS), harvest index (HI), dry matter of stem (DMS), dry matter of pointers (DMP), the relationship between dry matter of pointer and dry matter of stem (DMP/DMS) and total dry matter of the aerial segment (TDM) were determined. The variables SP, PP, DMS and DMP had a linear growth in proportion to WR increase, whereas HI and DMP/DMS adjusted to a quadratic model. Nitrogen fertilization affected positively the variables SP, HI, DMS and DMP/DMS and occurred interaction to TDM;also increasing the productivity stem and the harvest index.

Uncertainty in sap flow of Brazilian mahogany determined by the heat ratio method

The tropical arboreal species Brazilian mahogany(Swietenia macrophylla) is very important economically and ecologically,for which understanding ecophysiological variables such as sap flow will improve understanding of the species and its cultivation.This paper aims to measure uncertainties(U) involved in the application of the heat ratio method for determining sap flow in Brazilian mahogany using sets of heating probes and thermometers installed on plants of 18 months of age,cultivated in Yellow Latosol,under a weighing lysimeter and located in a protected environment.The uncertainty in sap flow was calculated as the combination of uncertainty in the thermal diffusivity(U_(k)),conductive section(U_(Sc)) and corrected sap velocity(U_(Vc)).U_(k) had greater weight in determining the flow of sap in Brazilian mahogany,when compared to U_(Sc) and U_(Vc).The thermal diffusivity during the cycle,or period evaluated,must be adjusted to improve the accuracy of the heat ratio method because the sap flow overestimated transpiration by 15.0%.When soil water was optimal In addition,the vapor pressure deficit linearly and indirectly influenced the SF with a difference of 14.6%.

Effect of Different Sources and Doses of Nitrogen on Vegetative and Productive Performance of Sugarcane under a Dystrophic Red Latosol Condition

The aim of this work was to evaluate the effects of the application of different sources and doses of nitrogen(N)in the growth and productivity of sugarcane in cane plant.Field experiments were conducted in the area of Rio Paraiso II farm,belonging to the Raízen factory,in the city of Jataí,GO.The soil was classified as dystrophic red latosol.The experimental design used was in randomized block,analysed in factorial scheme of 2×4×4,with three replications.The factors analysed were two sources of N(urea and ammonium nitrate),four doses of N(0,60,120 and 180 kg/ha)and four evaluation times(210,250,290 and 330 d after planting(DAP)).The parameters analysed were plant height(PH),diameter of stalks(DS),length of internodes(LI)and productivity of stalks(PS).Results observed significant difference in the sources and doses of N for the evaluated parameters in sugarcane plant.Urea in the average doses of 110 kg/ha and 100.87 kg/ha provided the greatest PH and LI of sugarcane,respectively.Ammonium nitrate at a dose of 180 kg/ha presented the largest DS of sugarcane(cane plant)at 330 DAP.The PS of sugarcane SP80-1816 at 60 kg/ha and 120 kg/ha ammonium nitrate has higher increments.For the PS,it is recommended the application of doses between 60 kg/ha and 120 kg/ha of N of the source ammonium nitrate in sugar cane(cane plant).