Agronomic and Economic Interactions between Sidedressed Nitrogen and Potassium Fertilizations on Atlantic Potato

Abstract Nitrogen (N) and potassium (K) in potato crop planting synergistically increase tuber yield, but there are no studies on this interaction in sidedressing. In two experiments with 'Atlantic' potato combinations of four N rates (0, 50, 100, and 150 kg ha-1) with four K2O rates (0, 100, 200, and 300 kg ha-1) were applied in sidedressing in a 4×4 factorial scheme with three replications in a completely randomized design. Adjacent commercial fields were sampled to economic comparisons with experimental results. Significant interaction between N and K sidedressing rates with tuber yields increase also was confirmed and classified as Liebig-synergism. Compared to the isolated N and K applications in sidedressing, joint N and K fertilizations, respectively, increases by 11% and 48% marketable tuber yields in the summer-fall experiment, and 12% and 7% in the spring experiment. Joint N and K applications as sidedressing was more profitable than planting fertilization, mainly at higher N and K rates. The response of specific gravity of 'Atlantic' potato tubers to the N and K sidedressing rates was mediated by interactions between edaphoclimatic conditions and inputs of N and K. The combined application of N and K sidedressing rates increased specific gravity in the summer-fall experiment, but had a negative effect in the spring experiment. Therefore, our results provide strong evidence that the fertilization management for potato crop in Brazil can be modified by applying higher amounts of N and K in sidedressing to match nutritional needs of the crop.

Factors affecting the success of resynchronization protocols with or without progesterone supplementation in dairy cows

The objective of this study was to investigate factors that influence the success of resynchronization protocols for bovines with and without progesterone supplementation. Cow synchronized and not found pregnant were randomly assigned to two resynchronization protocols: ovsynch without progesterone (P4) supplementation (n = 66) or with exogenous P4 administered from Days 0 to 7 (n = 67). Progesterone levels were measured on Days 0 and 7 of these protocols as well as 4 and 5 days post-insemination. Progesterone supplementation raised the P4 levels on Day 7 (p 3.5 had increased P/AI values while cows with BCS < 2.75 had decreased P/AI rates after P4 supplementation. Primiparous cows had higher P4 values on Day 7 than pluriparous animals (p = 0.04) and tended to have higher RRs (p = 0.06). Results of this study indicate that progesterone supplementation in resynchronization protocols has minimal effects on outcomes. Parity had an effect on the levels of circulating progesterone at initiation of the protocol, which in turn influenced the RR.

Efectividad de la terapia con leuprolide acetato de depósito cada tres meses en pubertad precoz central / Effectiveness of Leuprolide acetate therapy every three months in central precocious puberty

Background: Precocious puberty may reduce final adult height, and affected children may suffer social and emotional problems. The efficacy of treatment with a long acting agonist analogue of the gonadotropin releasing hormone (aLHRH) has been well demonstrated. Aim: To evaluated the efficacy of a new formulation of aLHRH (leuprolide, Lupron ®) for the suppression of gonadotropin activation and clinical signs of puberty. Material and methods: Eleven children (ten females) with idiopathic central precocious puberty, with a mean chronological age of 7.5±1.8 years and a bone age of 9.7±1.8 years were recruited. Testicular volume in the male was 15 ml. In females, Tanner stage for breast development was between 2-4 and mean ovarian volume was 2.3±0.8 ml. They were treated during 18 months with aLHRH, 11.25 mg administered intramuscularly every three months. Results: Clinical, hormonal and ultrasonographic signs of puberty regressed in all patients. The degree of suppression of LH was 87.7±5.1% at the end of the 18 months. No significant changes in bone mineral content were observed during the treatment period. Conclusions: Leuprolide (aLHRH) 11.25 mg, injected every three months, is effective for the control of central precocious puberty and allows to reduce the number of yearly injections from 12 to 4.