Cotton has been widely cultivated in the Cerrado region, including the crop-livestock integration system under no-till. The objective of this study was to evaluate the effects of plant residues from ruzigrass [Urochloa ruziziensis (R. Germ. C.M. Evrard) Crins] and nitrogen fertilization on nitrogen use efficiency, growth, and yield of cotton crop (Gossypium hirsutum L. R. latifolium Hutch.), cv. TMG 44 B2RF. The experimental design was randomized blocks, in a split plot scheme, with four replications. The plots consisted of three production systems: i) conventional cotton cropping in fallow area; ii) cotton cropping in the presence of straw from the shoots and roots of ruzigrass plants; iii) cotton cropping only in the presence of residues from the ruzigrass roots. The subplots consisted of five rates of N (0, 40, 80, 120 and 160 kg ha–1), applied at 30 and 50 days after seedling emergence. The presence of ruzigrass straw provided less growth and development of cotton, in addition to less N uptake by plants. The cotton cropping in the crop-livestock integration system in the presence of residues from the roots and shoots of the ruzigrass plants resulted in the greater cotton yield in the second year, demonstrating the importance of the straw formation of the cover crops for the sandy soils of the Cerrado region. The optimal application rate of N in topdressing for the cropping of cotton in succession or not with ruzigrass residues in sandy soil varies from 100 to 110 kg N ha–1.
The adequate amounts of potassium (K) fertilizer application may play an essential role in the growth and tolerance of plants against the drought stress. In this study, the role of K in mitigating the adverse effects of drought stress on soybean plants [Glycine max (L.) Merrill.] was investigated in greenhouse conditions. Treatments were arranged in a randomized block design in a 2 × 3 factorial: two potassium fertilizer levels [40 mg K kg–1 (low) or 160 mg K kg–1 (high)] and three irrigation regimes [100% of pot capacity – PC (well watered control), 50% of PC (moderate stress) and 25% of PC (severe stress)] with four replicates. Leaf relative water content, cell membrane stability, plant growth, and morphophysiological indexes were recorded after 18 days of exposure to drought stress. The appropriate supply of potassium fertilizer improved leaf membrane stability and minimized the water loss from leaf tissue of soybean plants exposed to drought stress. The adverse effects of drought on leaf abscission and pod abortion rate could be mitigated by adequate K supply. The appropriate supply of potassium fertilizer alleviates the negative effects of drought stress and maintain shoot growth and the water status soybean plants, and therefore, the proper management of potassium fertilization may confer greater drought tolerance.
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