Soya bean yield gap can be caused by different factors resulting in uncertainties when the objective is to use such information for farm decision‐making and reference yield determination. Thus, this study aimed to quantify the soya bean yield gap for four sites, located in Southern and Midwestern Brazil, as well as the uncertainties of that related to cultivars, sowing dates, soil types and reference yields. The crop simulation model DSSAT‐CSM‐CROPGRO‐Soybean was calibrated for cultivars with similar maturity groups, based on the data obtained from the best farmers at the county level. The yield gap by water deficit (YGWD) was obtained through the difference between potential and attainable yields, and that one caused by sub‐optimum crop management (YGCM) by subtracting actual yield of each county, obtained from official statistics between 1989/90 and 2014/15 growing seasons, from the estimated attainable yield. The yield was simulated using four sowing dates, three soil types and two soya bean maturity groups by county. The reference yield uncertainty was quantified using yield reference from crop model and regional winners of the soya bean yield context, conducted by CESB (Brazilian Soybean Strategic Committee), for the growing seasons from 2013/14 to 2015/16. The crop model showed a good agreement between measured and simulated crop development and growth using calibration by maturity group, with low root mean square error (347 kg/ha). Southern sites had a mean YGWD of 1,047 kg/ha, while in the Midwest, it was lower than 100 kg/ha. The YGCM was 1,067, 528, 984 and 848 kg/ha, respectively, for Castro, PR, Mamborê, PR, Montividiu, GO and Primavera do Leste, MT, representing the opportunity for yield gain when having the best farmers as reference. The maturity groups, sowing dates and soil types showed to be an important source of uncertainty for yield gap determination, being recommended to investigate the farms in detail for an appropriate quantification. The reference yield showed expressive uncertainties, with some farmers presenting conditions to increase their soya bean yields by more than 3,000 kg/ha, when considering as reference the yields obtained by the winners’ farmers. These results show that uncertainties must be reduced when assessing farm yield gaps, in order to ensure that expected rate of soya bean yield growth could be reached by adopting the same technologies from CESB winners and best farmers in the county as a reference.
Productivity in clonal eucalyptus plantations depends on the genetic material and on the demand and cycling of nutrients, making studies that evaluate these requirements necessary. The aim of this study was to evaluate the effect of management (with and without thinning) on the deposition, chemical composition and nutrient contribution in litter at different clonal or stallion eucalyptus plantations. The experiment was conducted under a subdivided plot design for comparison of "clone" and "thinning" treatments. Plots were composed of eight different clonal and eucalyptus seed plantations, with subplots being areas where thinning was performed and areas without thinning. Litter deposition pattern associated to seasons was observed, with higher values in the spring and summer. The leaf fraction was more representative in relation to nutrients. Deposition values were close in most plantations. Nutritional contents were higher in leaves of areas with thinning in relation to the other areas.
The objective of this work was to evaluate genotypes of wheat depending on doses of N in order to determine the best value of N and the components of productivity of wheat. Experiment was carried out in Pato Branco-PR in soil classified as Eutrophic typical RED LATOSOL. The experimental design was randomized blocks, in 3 × 5 (× N doses genotypes), with three repetitions. The genotypes were: CD 108, CD 115 and BRS 220, and the doses of n were: zero; 20; 40; 80 and 120 kg of N•ha −1 , applied at the beginning of tillering. After harvest assessed number of Spike (NE), Tang (EC) length, grains per Spike (GE), mass of thousand grains (MMG), grain yield (R) and weight/HL (PH), application of N increased the NE and R, and however decreased to MMG. The genotypes differed among themselves, featuring better performance of the NE (the BRS 220), CE (the CD 115) and R (the CD 108). There were positive correlations between the doses of N with the NE and R and between NE with the R, and negative correlation between doses of N with the MMG. It is concluded that the NE is the main factor that affects the R with N supply.
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