Partitioning of environmental and taxonomic controls on Brazilian foliar content of carbon and nitrogen and stable isotopes

The Neotropics harbor some of the most diversified woody species in the world, and to understand the nutrient dynamics in these ecosystems, it is crucial to understand the role of plant taxonomy. In addition, biological nitrogen (N) fixation (BNF) in the tropics is one of the key processes affecting the global N cycle. Our objective was to (i) investigate the role of taxonomy and sampling site as predictors of foliar carbon (C) and N concentration and its stable isotopes (i.e., δ13C and δ15N); (ii) assess differences in foliar N, C:N ratio, and δ15N among three functional groups: species of N2-fixers and non-fixers of the Fabaceae family, as well as non-Fabaceae species; and (iii) examine the effect of wood density on tree foliar properties. We hypothesized that Fabaceae specimens in symbiosis with N2-fixers would possess a higher foliar N than non-fixing plants, including those of the Fabaceae family, as well as high-density trees would have higher foliar C and C:N ratio relative to low-density trees, where the latter invest in nutrients instead of structural C. We used a data set composed of 3,668 specimens sampled in three main biomes of Brazil: Amazon, Atlantic Forest, and Cerrado. The partitioning of variance had a higher influence of taxonomy on leaf C, N, and C:N ratio. Conversely, foliar δ13C and δ15N were environmentally constrained. While family was the most important taxonomy level for C, N, and C:N ratio, species played a major role for δ13C and δ15N. Foliar N followed the pattern fixers > non-fixers > non-Fabaceae, while C:N ratio had an opposite trend. In addition, foliar C was correlated with wood density, where high-density > medium-density and low-density woods. The large variability of δ15N was observed among Fabaceae species, demonstrates the complexity of using δ15N as an indicator of BNF. The higher foliar N of Fabaceae non-fixers than non-Fabaceae specimens support the hypothesis that an N-demanding lifestyle is an inherent pattern in this family. Lastly, although observed in some studies, the prediction of foliar properties using wood density is challenging, and future research on this topic is needed

Evaluation of phosphate rock sources and rate of application on oil palm yield grown on peat soils of Sarawak, Malaysia

Malaysia has 2.4 million ha of peat and this type of soil is very poor in phosphorus and needs P application. As there are various sources of P fertilizer in the Malaysian market, it is crucial for growers to apply the most effective source for their crops. In this research, two sources of phosphate rocks available in the local fertilizer market from Christmas Island (CIPR) and Morocco (MPR) at four rates were evaluated for maximum yields of Fresh Fruit Bunches (FFB) from oil palm grown on peat soils in Sarawak, Malaysia. The CIPR and MPR at the rates of 0, 500, 1000 and 2000 g plam-1 year-1 were applied annually. FFB ha-1, average weight bunch-1 and leaf and soil nutrient concentrations were determined. Results showed that MPR treatments produced higher available soil P than CIPR treatments by average of 87% and also higher leaf P concentrations (up to 0.185%). Pearson’s correlation indicated that available soil P was negatively correlated with K, Mg, B, Cu and Zn but positively correlated with Ca. In addition, P concentrations in leaves were positively correlated with Ca, Mg, B and Zn but were negatively correlated with K and Cu. Correlation of yield parameters and leaf nutrient concentrations revealed that bunch weights were negatively correlated with leaf P concentrations, Mg and B, whilst the total yield was negatively correlated with Mg and B. Maximum yields were obtained at CIPR-2000 and CIPR-1000 treatments. By interpolation maximum yields in MPR would be attained at MPR-750 treatment

Effects of cover crops and phosphorus sources on maize yield, phosphorus uptake, and phosphorus use efficiency

Core Ideas Phosphorus recycling by cover crops in a typical Brazilian cropping system. Maize response to phosphate sources under no‐till management. Residual effects of phosphate sources in tropical weathered soils. Rock phosphate was more effective than soluble phosphate in supplying P for maize over time. This research evaluated the potential benefits of winter cover crops on the utilization and cycling of P in Brazilian tropical cropping systems. The effect of P fertilizer [none, rock phosphate (RP), and soluble phosphate (single superphosphate, SSP)] in combination with cover crop residues (common vetch [Vicia sativa L.], white lupin [Lupinus albus L.], forage radish [Raphanus sativus L.], ryegrass [Lolium multiflorum Lam], black oat [Avena strigosa Schreb.], red clover [Trifolium pratense L.], and fallow) were evaluated on maize (Zea mays L.) yield and P use efficiency over three maize cropping seasons under no‐tillage, from 2009 to 2012. Cover crop yields and P uptake were higher under phosphate fertilizers than nil‐P across all seasons evaluated. The highest amounts of P recycled in cover crops over the period were under white lupin, followed by radish and ryegrass, but without any significant cover crop effect on maize yield. The largest response and greatest P use efficiency (30 kg grain per kg P applied) was obtained in the third year of evaluation, when maize yield was restricted by low rainfall. In this year, RP promoted greater maize yield than SSP and the nil‐P. Soil available P at the end of the experiment was higher under RP than SSP. It is concluded that RP solubility is higher than currently predicted (9% P2O5 in citric acid). Cover crops were not able to affect maize yield after 3 yr of leaving the residues on the surface, however they can reduce the soil loss by erosion and runoff

Effects of different levels of molybdenum on uptake of nutrients in rice cultivars

A hydroponic trial was carried out to determine the effect of molybdenum (Mo) on utilization and uptake of macro and micronutrients in different rice cultivars. The experiment was conducted using a randomized complete-block design, with a split-plot arrangement of treatments and three replications. Four rates of Mo (0, 0.01, 0.1 and 1 mg L-1) and five cultivars (MR219, HASHEMI, MR232, FAJRE and MR253) provided the main and sub-plots, respectively. The results showed that the enhancement of Mo levels (from 0.01 to 0.1 and 0.1 to 1mg L-1) led to increase of root Mo uptake by 81.7 and 61.6% and shoot Mo uptake by 43 and 87%, respectively. Also, Mo application significantly affected shoot Phosphorus uptake so that highest shoot Phosphorus (P) uptake (0.43% plant-1) was achieved at 1mg Mo L-1 but there was no significant influence on root P uptake. Shoot Iron (Fe) uptake was inversely proportional to increment of Mo rates therefore, the highest rate of shoot Fe (59.05 μg plant-1) was obtained in treatments with least amount of applied Mo. Also, increase in Mo application enhanced manganese (Mn) uptake of shoot but there was no significant effect on Mn root uptake

Effect of zinc and phosphorus supply on the activity of carbonic anhydrase and the ultrastructure of chloroplast in sweet corn (Zea mays var. saccharata)

Phosphorus (P) and zinc (Zn) interact with each other and this interaction can affect the yield of corn plants. This study was conducted to examine the effect of different levels of P and Zn on the ultrastructure of chloroplast and physiological characteristics of corn plants. Sweet corn was grown in nutrient culture containing all combinations of P at levels of 0.0 and 80.0 mg L-1 as KH2PO4 and Zn at levels of 0.0 and 20.0 mg L-1 as ZnSO4.7H2O and harvested at 14 and 28 days after transplanting. Phosphorus (P) and zinc (Zn) concentrations in leaves increased with increasing P and Zn concentration in nutrient solution. Zinc supply did not affect P concentration but Zn concentration reduced with increasing P supply in nutrient solution at both harvests. The lowest amount of chlorophyll content was recorded in Zn20P0 treatment due to the interaction of Zn with iron in the growth medium. Carbonic anhydrase activity in leaves was enhanced with increasing Zn levels and decreased with increasing P levels at both harvest times. Carbonic anhydrase activity is a better indicator of Zn nutritional status than Zn concentration alone. The ultrastructure of chloroplast was affected with P and Zn supply

Sulfur and molybdenum fractionation in marine and riverine alluvium paddy soils

Intermittently submergence and drainage status of paddy fields can cause alterations in morphological and chemical characteristics of soils. We conducted a sequential fractionation study to provide an insight into solubility of Sulfur (S) and Molybdenum (Mo) in flooded alluvial paddy soils. The samples (0–15 and 15–30 cm) were taken from marine and riverine alluvial soils in Kedah and Kelantan areas, respectively, and were sequentially extracted with NaHCO3, NaOH, HCl, and HClO4–HNO3. Total S in upper and lower layers of Kedah and Kelantan ranged between 273 and 1121 mg kg−1, and 177 to 1509 mg kg−1, respectively. In upper layers and subsoil of Kedah, average total Mo were 0.34 and 0.27 mg kg−1, respectively. Average total Mo in Kelantan were 0.25 mg kg−1 (surface layer) and 0.28 mg kg−1 (subsoil). Cation exchange capacity (CEC) was positively correlated with plant available amounts of Mo in upper layers of Kedah area. Also, total and medium-term plant-available S was correlated with total carbon (C) at lower layers of Kelantan soil series. But in surface layers of Kelantan soil series, CEC was strongly correlated with total and medium-term plant-available S. Our results indicates that the influence of flooding conditions on soil S and Mo contents in paddy fields may cause long-term changes in S and Mo chemical reactivities

Interaction effects of Phosphorus and zinc on their uptake and 32P absorption and translocation in sweet corn (Zea mays var. Saccharata) grown in a tropical soil

Zinc (Zn) and Phosphorus (P) interact with each other and this interaction can result in impact on the yield of corn plants. This study was conducted to examine the effect of different levels of Zn and P on the yield, Zn and P concentration and uptake, chlorophyll content and percentage of P derived from fertilizer of corn plants in a tropical soil. Sweet corn grown in pot culture containing all combinations of Zn at levels of 0.0, 5.0 and 10.0 mg kg-1 soil and P at levels of 0.0, 50.0, 100.0 and 200.0 mg kg-1 soil as ZnSO4.7H2O and KH2PO4, respectively and harvested at 28 days after transplanting. Dry matter yield increased with P supply, while Zn application did not show any significant effect on this parameter. The Zn and P uptake by shoots increased with increasing Zn and P application into the soil. The Zn concentration in shoots decreased with increasing P supply but P concentration and uptake enhanced. Phosphorus (P) induced Zn deficiency in this study mostly related to the dilution effect. Chlorophyll a/b ratio increased with P supply. The percentage of P derived from fertilizer reduced with increasing Zn application, although P uptake by shoots was unchanged

Biological and morphological traits of sugarcane roots in relation to phosphorus uptake

Appropriate management of phosphorus (P) in soil will lead to higher yields and sustainability for sugarcane production. Our study evaluated the importance of differences in root structure and function, and the differential composition of the bacterial community in four sugarcane cultivars, in relation to the efficiency for P uptake and also to assess changes in soil P with distance from the rhizoplane. Experiments were performed in pot trials using a sandy clay loam Ferralsol. In the first experiment, the effect of P application (78.4 mg P kg-1 soil as triple superphosphate) on sugarcane cultivars RB92-579; RB85-5156; RB86-7515 and RB96-6928 was investigated. Secondly, we evaluated P rates of 0; 9.8; 19.6; 39.2 and 78.4 mg kg-1 soil using cultivar RB96-6928 which was shown to be one of the more growth responsive cultivars. The cultivar RB96-6928 exhibited the highest root dry matter and root surface area, while the bacterial communities found in the rhizosphere of these plants were not different from other cultivars, as determined by PCR-DGGE. From the P dose-dependent experiment for this cultivar, optimal plant performance occurred at a P supply up to 38.5 mg P kg-1 soil. Collectively, our results indicate that P efficiency in sugarcane was predominantly associated with the generation of high root biomass and surface area

Interaction effects of zinc and manganese on growth, uptake response and chlorophyll content of sweet com (Zea mays var. saccharata)

Manganese (Mn) and Zinc (Zn) interact with each other and this interaction can result in impacts on the yield of corn plants. This study was conducted to examine the effect of different levels of Mn and Zn on the yield, Mn and Zn concentration, root growth parameters and chlorophyll contents of corn plants. Sweet corn was grown in nutrient culture containing all combinations of Zn and Mn at levels of 0.0, 0.1, 1.0 and 10.0 mg L-1 as ZnSO4.7H2O and MnSO4.H2O, respectively and harvested at 28 days after transplanting. Mn and Zn concentrations in roots and shoots increased with increasing Mn and Zn concentration in nutrient solution. Zn concentration in both roots and shoots enhanced with increasing Mn levels. Mn concentration in shoots did not show any correlation with Zn concentration in nutrient solution, but Mn concentration in roots decreased with increasing levels of Zn. Zn0Mn1 treatment produced the highest yield. The lowest dry weight of young corn plants was recorded under Zn10Mn0 treatment due to Mn deficiency. Chlorophyll content decreased with high Zn application and this can be attributed to the interaction of Zn with iron in the growth medium. Different levels of Zn and Mn in nutrient solution did not have any significant effect on root parameters