Superabsorbent polymers (SAP) enhance efficient and eco-friendly production of corn (Zea mays L.) in drought affected areas of northern China

In arid and semiarid regions of northern China, there is an increasing interest in using reduced rate of chemical fertilizer along with water-saving superabsorbent polymer (SAP) for field crop production. The objective was to evaluate the effectiveness of different rates of SAP (low, 0.75; medium, 11.3 and high, 15.0 kg ha-1) against half amount of conventional standard rate of chemical fertilizer for summer corn (Zea mays L.) production in a drought-affected field of northern China. Corn yield increased following SAP application by 11.2% under low 18.8% under medium and 29.2% under high rate with only half amount (150 kg ha-1) of fertilizer compared with control plants, which received conventional standard fertilizer rate (300 kg ha-1). At the same time plant height, stem diameter, leaf area, biomass accumulation and relative water content as well as protein and sugar contents in the grain also increased significantly following SAP treatments. The optimum application of SAP in the study area would be 15 kg ha-1 as it brings progressive increase in corn growth and also maintain proper nutrients balance in the soil after harvest. Other rates are not sufficient to maintain proper plant growth or soil nutrient balance against half fertilizer. We suggest that, the application of SAP at 15 kg ha-1 plus only half the amount of conventional fertilizer rate (150 kg ha-1) would be a more appropriate practice for sustainable corn production under arid and semiarid conditions of northern China or the areas with similar ecologies.Key words: Corn, drought stress, fertilizer use efficiency, northern China, superabsorbent polymer

Silicon uptake by a pasture grass experiencing simulated grazing is greatest under elevated precipitation

Background Grasses are hyper-accumulators of silicon (Si) and often up-regulate Si following herbivory. Positive correlations exist between Si and plant water content, yet the extent to which Si uptake responses can be mediated by changes in soil water availability has rarely been studied and never, to our knowledge, under field conditions. We used field-based rain-exclusion shelters to investigate how simulated grazing (shoot clipping) and altered rainfall patterns (drought and elevated precipitation, representing 50% and 150% of ambient precipitation levels, respectively) affected initial patterns of root- and shoot-Si uptake in a native Australian grass (Microlaena stipoides) in Si-supplemented and untreated soils. Results Si supplementation increased soil water retention under ambient and elevated precipitation but not under drought, although this had little effect on Si uptake and growth (tiller numbers or root biomass) of M. stipoides. Changes in rainfall patterns and clipping had strong individual effects on plant growth and Si uptake and storage, whereby clipping increased Si uptake by M. stipoides under all rainfall treatments but to the greatest extent under elevated precipitation. Moreover, above-ground–below-ground Si distribution only changed following elevated precipitation by decreasing the ratio of root:shoot Si concentrations. Conclusions Results highlight the importance of soil water availability for Si uptake and suggest a role for both active and passive Si transport mechanisms. Such manipulative field studies may provide a more realistic insight into how grasses initially respond to herbivory in terms of Si-based defence under different environmental conditions

Land Clearing Effect on the Variability of some Soil Properties of an Alfisol in South-Western Nigeria

The variability of some soil properties of a mechanically cleared plot was compared with an adjacent plot under natural vegetation in an Alfisol of South-western Nigeria. The soil properties studied were pH, total N, available P, exchangeable acidity Ca, Mg, A/a, K and effective cation exchange capacity (ECEC), organic matter and particle size fractions. Land clearing increased the variability of total N, exchangeable acidity, Ca, Mg, Na and ECEC while it decreased that of available P, exchangeable K, organic matter and soil texture. The variability groupings differed between the plots for available P, exchangeable Mg and silt content. Results of t-tests showed significant differences between the plots for total N, exchangeable Ca and organic matter

An Assessment of some Fertilizer Recommendations under Different Cropping Systems in a Humid Tropical Environment

Studies were carried out to determine the effects of four fertilizer recommendation systems (bianket recommendation, soil test recommendation, recommendation based on nutrient supplementation index and unfertilized control) on five cropping systems (sole cassava, maize, melon, cassava + maize and cassava + maize + melon). The experiment was a split-plot in randomised complete block design, with fertilizer recommendation systems in main plots and cropping systems in subplots. Observations were made on plant growth and yield. Plant samples were also analyzed for N, P and K uptake. Cassava and melon gave higher yields in sole cropping than intercropping while maize yield under intercropping exceeded that under sole cropping by 17 %. Cassava root yield was significantly reduced by 24 and 35 % in cassava + maize and cassava + maize + melon plots. Fertilizer recommendation based on nutrient supplementation index (NSI) gave the highest crop yield 41, 31, and 27 t/ha of maize in sole maize, maize + cassava and maize + cassava + melon and 0.6 and 0.2 t/ha of sole melon and intercropped melon respectively. Nitrogen uptake by cassava and maize was highest under NSI, but fertilizer recommendation based on soil test gave the highest crop yield and monetary returns per unit of fertilizer used