Nitrogen fertilizer management criteria for potato in two planting seasons / Critérios para o manejo da adubação nitrogenada da batata em duas épocas de plantio

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The objectives of the thesis were: a) to establish the leaf SPAD critical level; b) to quantify pre-planting and sidedress nitrogen (N) rates to obtain the maximum commercial potato yield; c) to determine the productivity, profitability, N use efficiency and morfo-anatomical characteristics of the potato fourth leaf in relation to N fertilizer management criteria. Experiments were set in the rain and dry seasons with Monalisa cultivar and ammonium sulphate. In the first experiments were combined five pre-planting N rates (0, 50, 100, 200 and 300 kg ha-1) and four sidedress N rates (0, 100, 200 and 300 kg ha-1) applied 21 days after plant emergence. The experiments were installed in randomized complete block split-plot design with four repetitions. In the last experiments, N fertilizer management criteria, partially derived from the previous experiments, were evaluated. The criteria were: 1) Test: no N fertilizer; 2) Fertot: optimum N rate determined from previous year experiment; 3) Quinapr: MG State recommendation; 4) Prodvin: N rate based on the expected tuber yield, being 20% of the N rate at pre-lanting; 5) Prodcin: equal to 4, but with 50% at pre-planting; 6) Prodoit: equal to 4, but with 80% at pre-planting; 7) Prodcem: equal to 4, but with 100% at preplanting; 8) SPAD1: pre-planting N rate based on MG recommendation and sidedress N based on 100% of leaf SPAD critical value (CV); 9) SPAD2: equal to 8, but with 90% of CV; 10) SPAD3: equal to 8, but with 110% of CV; 11) Soil1: soil N content + N fertilizer rate to complete the N amount that propitiated the optimum commercial tuber yield in the previous year experiment and 12) Soil2: soil N content + MG State recommendation. The last two criteria were only tested at the wet seasons. The experiments were installed in randomized complete block design with six repetitions. In the dry season, the maximum commercial potato tuber yield was 39.72 Mg ha-1 with 185.8 kg ha-1 of N at pre-planting and in the wet season it was 44.36 Mg ha-1 with 205.85 kg ha-1, being 50 kg ha-1 at pre-planting and the remainder as sidedress. Associated to the N rates that provided the maximum commercial yields in dry and wet seasons, SPAD critical values were 42.1 and 35.2, respectively, determined at 21 days after plant emergence in the fourth leaf leaflet. The conjunct analysis of the experiments showed that planting seasons and N fertilizer management criteria influenced the potato commercial yield. The highest yield was obtained in the wet season and the highest net profit was attained with number 6 criterion. In the two seasons, the absorption and agronomic N efficiencies were influenced by the N fertilizer management criteria. Fourth leaf leaflet morfo-anatomical characteristics, as area, crystal numbers, estomatic index in the abaxial face, stomata guard cell length in the adaxial face and above the main rib chollenchyma length were altered by planting seasons and N fertilizer management criteria in potato crop.

ASSUNTO(S)

clorofilômetro fitotecnia eficiência nutricional solanun tuberosum produtividade nitrogen fertilizer nutritional efficiency yield solanun tuberosum adubação nitrogenada

ACESSO AO ARTIGO

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