Synopsis Differences in soil fertility influenced the amounts of N, P, and K taken up by corn plants, but did not markedly change the seasonal pattern of uptake and distribution of these elements in the plants. Large proportions of the N and P and a small proportion of the K were translocated from other plant parts to the grain. Late in the season K was lost from the leaves to the stalks.

RESUMO-Este trabalho foi conduzido para se avaliarem produtividade e as características morfológicas de cinco híbridos de milho Pioneer: superprecoce P32R21, os precoces P30R07, P3041, P30F33 e o semiprecoce P30F80, em cinco estádios de maturação. O delineamento utilizado foi de blocos ao acaso, com cinco tratamentos e quatro repetições. A colheita das amostras dos híbridos de milho foi adotada estimando-se cinco estádios de maturidade da planta: 30, 34, 38, 42 e 46% de matéria seca. Por ocasião da colheita, no primeiro estádio de maturação, foram tomados alguns parâmetros para avaliação, como altura da planta, altura inserção de espiga, peso da planta, diâmetro de colmo e número médio de espigas. Para cada estádio de maturação, procedeu-se à separação de colmo + bainha, lâmina foliar, grão, sabugo e palha. Os híbridos superprecoce P32R21 e o precoce P3041 apresentaram maiores peso, diâmetro de colmo e altura de planta. As produções de matéria seca (MS), massa verde, grãos, lâmina foliar e colmo + bainha, expressas em toneladas/ha, diferiram entre os híbridos avaliados e houve efeito de dias pós-plantio (DPP). O aumento na produção de MS verificado com o avanço do estádio de maturidade dos híbridos foi correlacionado positivamente com o aumento da produção de grãos (R 2 = 64,3%). A produção de MS correlacionou-se positivamente com a percentagem de espiga (R 2 = 56,0%) e negativamente (R 2 =-56,7%) com a percentagem de colmo + bainha (em relação a planta inteira). ABSTRACT-This study was conducted to evaluate productivity and morphologic traits of five hybrids of Pioneer corn: P32R21, P30R07, P3041, P30F33 and P30F80 at different maturity stages. The treatments were used in plots of 7 x 8 m in a randomized block design, with four replicates. The samples collected, of corn hybrid, were adopted trying to estimate phases of maturity of the plant (30, 34, 38, 42 and 46% of dry matter [DM]). In the first maturation stage, some parameters (plant height, the ear of the corn insertion height, plant weight, stem diameter, number medium of ears of the corn) were evaluated, at harvest. For each maturation stage, was done separation of stem + sheath, leaf lamina, grain, cob and straw. The hybrid P32R21 and P3041 presented shown weight, diameter stem and plant height. Dry matter (DM) yield, green material, grain, leaf lamina, and stem + sheath, expound t/ha at hybrids were different and presented significance at days after seeding (DAS). The increase the productivity DM verify with the advanced the maturity stage hybrids, correlations positively with increase the production grain (R 2 = 64.3%). Too the production DM correlations positively with concentration ear (R 2 = 56.0%) and negatively (R 2 =-56.7%) with the concentration stem + sheath (in relation a whole plant).

Effects were studied of fertilizer applications for nodulating and non‐nodulating soybeans and of varieties on the amounts of N, P, and K accumulated in aboveground plant parts of soybeans at successive stages of plant development. Total accumulation of N, P, and K in the plants followed patterns similar to that of drymatter accumulation. Rates of accumulation were slow early in the season, but became rapid, and the nutrients accumulated at constant daily rates between stages 5 and 9. Approximately 79% of the total accumulation of these nutrients occurred during the 46‐day period between stages 5 and 9. Approximately half of the N, P, and K in the mature seeds were translocated from other plant parts, and the remaining half taken up from the soil and nodules during seed development. Fertilizer applications increased the amounts of N, P, and K accumulated by the plants. Nutrient accumulation was similar in 8 varieties.

Measurements made over a 4‐year study of flow and NO3‐N, PO4‐P, total P, and SO4‐S content of subsurface drainage water from tile‐drained cropland indicate that annual nutrient losses are highly variable. Annual losses of phosphorus, SO4‐S, and NO3‐N ranged from 0 to 0.04, 0 to 32, and 0 to 93 kg/ha, respectively, being very dependent on the amount of water lost. Because of low concentrations of phosphorus, losses with subsurface drainage water were insignificant when compared with losses associated with surface runoff. Concentrations of SO4‐S and NO3‐N were seemingly inversely related. Tile drainage water with consistently high NO3‐N content relative to surface runoff (> 10 ppm even under the low‐fertility management of this study, 224 kg/ha of N over 5 years) is believed responsible for the high NO3‐N content sometimes found in a river draining central Iowa. The nitrate content of water from the saturated and unsaturated zones of the soil profile indicates that waves or pulses of water, with different NO3‐N concentrations, moving through the soil profile cause the observed variation of NO3‐N content of subsurface drainage water with time and flow rate. Such variations illustrate the difficulty of identifying water‐quality trends from limited data.

Foliar fertilization of soybeans (Glycine max (L.) Merr.) with N, P, K and S during the seed‐filling period promises to increase soybean yields. Such foliar applications could be used to avoid the depletion of these nutrients in the leaves and the resulting reduction in photosynthetic rate during this period due to poor nutrient uptake from the soil and translocation of these elements from the leaves to the developing seeds. Field experiments were conducted to test this hypothesis by spraying soybeans with solutions of N, P, K, and/or S in different proportions and at different times and rates. We supplied N primarily as urea, P primarily as poly‐phosphate, K with the P as potassium polyphosphate or with the S as potassium sulfate. Very significant yield increases were obtained from two to four sprayings on different soybean cultivars at different experimental sites between developmental stages R5 and R7. The optimum proportion of N:P:K:S in the solution 10:1:3:0.5. a proportion similar to that of these elements in the seeds. The optimum rate of total nutrient application was about 80 + 8 + 24 + 4 kg/ha of N + P + K + S, respectively. Yield increases were due to increases in numbers of harvestable seeds, not seed size. The results indicate that foliar fertilization during the seed‐filling period can become a very practical method for increasing soybean yields.