Scielo RSS <![CDATA[Journal of soil science and plant nutrition]]> vol. 16 num. 2 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b>Influence of clay concentration, residue C/N and particle size on microbial activity and nutrient availability in clay-amended sandy soil</b>]]> The low fertility of sandy soils can be ameliorated by addition of clay-rich soil, but the effect of clay may differ between high and low C/N residues and could be modulated by residue particle size. An incubation experiment was conducted with addition of a clay-rich subsoil (73% clay) to a sandy soil (10% clay). The final clay concentrations were 10, 15, 20 and 30% (w/w). The residues of young kikuyu shoots (C/N 14) and mature wheat shoots (C/N >120) in two particle sizes (0.2-2 and 3-4 mm) were added at 10 g kg-1 soil. Soil respiration, pH, available N, microbial biomass C (MBC), N and P were measured. Cumulative respiration was up to 4-fold higher with kikuyu than with wheat and 30% lower at the highest clay concentration. The MBC concentration was up to 2-fold higher with kikuyu than with wheat. The available N concentration was up to 2-fold higher with kikuyu than with wheat and up to 50% lower at highest clay concentration. Thus, clay addition to sandy soils may reduce nutrient availability by reducing accessibility of plant residues to microbes and binding of nutrients, but this clay effect is not influenced by residue C/N or particle size. <![CDATA[<b>Fertilizer effects on phosphorus fractions and organic matter in Andisols</b>]]> Andisols are characterized by a high phosphorus (P) fixation capacity, which is a limiting factor for plant production. Continuous application of P fertilizer may result in an accumulation of P associated with soil organic matter (SOM), which further acts to reduce the availability of the added P. The objectives of this study were (1) to evaluate the impact of P fertilizer inputs on the quantities and chemical forms of P, and (2) to investigate relationships between P forms SOM and land use. Topsoil (0-20 cm) and subsoil (20-40 cm) samples were taken from two Andisols series under grassland and arable cropping. Soil P forms were determined using sequential fractionation, while SOM analysis involved a combination of 13C nuclear magnetic resonance (NMR) spectroscopy and pyrolysis-GC-mass spectrometry. Fertilization increased total P, total organic P, organic carbon, and inorganic P fractions, mainly in arable soils. Labile P was higher in grassland (3% of total P) than in arable soils (1% of total P). A clear effect of fertilization was observed on organic matter compounds measured by pyrolysis in both soil depths. Interestingly, the polysaccharide-derived compounds increased in fertilized soils and lipid-derived compounds decreased. Thus fertilization principally affected labile P and labile SOM forms, whereas recalcitrant forms of P and SOM remained unchanged. <![CDATA[<b>Can biochar increase the bioavailability of phosphorus?</b>]]> A large proportion of phosphate (P) fertilizer applied to Andosols reacts with reactive aluminum (Al) and iron (Fe) to become unavailable for plant uptake. We investigated whether biochar could enhance plant growth by (i) mobilizing soil P through changing soil pH or facilitating the growth of arbuscular mycorrhizal fungi (AMF), and/or (ii) introducing additional P. We grew Lotus pedunculatus cv barsille in two Andosols of contrasting P status amended with three biochars (with distinct porosity, nutrient and liming properties) at a dose of 10 t ha-1 for 32 weeks. The growth medium was divided into a root and a hyphal zone through a nylon mesh and a tephra layer that allowed the P in the hyphal zone to be transferred only by AMF hyphae. The addition of a relative nutrient-rich biochar (e.g. made from willow woodchips) with liming properties to the root zone of the P-deficient soil increased plant growth by 59% and P uptake by 73%. Pine-based biochar provided no extra nutrient acquisition and no plant-growth stimulation when added to the root zone of the P-deficient soil. However,when hyphae of those plants had access to a P-rich soil patch, the presence of pine biochar in the soil patch greatly enhanced P uptake and plant growth (e.g., by 76% and 40% when using biochar produced at 450ºC compared to the absence of it). None of the tested biochars conferred advantages in the root zone of a high-P soil. We concluded that the benefits from biochar addition to nutrient uptake and plant growth are biochar- and soil-specific. Thus, biochars need to be tailored-made for certain soils by optimizing feedstock and pyrolysis conditions before application. <![CDATA[<b>Impacts of soil-soluble anions on wild and cultivated herbaceous species: implications for soil phytoremediation</b>]]> This study addresses the growing problem of soil salinity. In Mediterranean regions, disused solid waste landfills have given rise to disturbed ecosystems. At such sites, both mobile soil anions and cations have toxic effects on plants. Thus, detailed knowledge of these effects is needed for the phytoremediation of soils facing the problem of salinization. In this study, high chloride levels were detected in soil samples from several sealed waste landfill sites showing metal pollution. We also examined the nutrition behaviour of six native and five cultivated herbaceous species (two forage species and three for human consumption) grown in soils containing zinc chloride. Based on the tolerance shown by Lolium rigidum to this salt in a first bioassay, we assessed its behaviour in the presence of other chlorides and other Zn salts (sulphates and nitrites). Besides providing plant anion concentrations (which are particulary novel results), our study identified Lolium rigidum as a species able to well-tolerate soil salinity and accumulate high levels of zinc chloride indicating its possible use for the phytostabilization of soils polluted with this salt. <![CDATA[Selection of maturity indices for compost derived from grape pomace]]> Compost quality is usually determined through chemical composition and sanitary parameters; however it is necessary to determine more precise maturity indices. The objective of this work was to identify sensitive properties to measure compost maturity using a novel approach based on quality indices. Nine mature compost piles were sampled and analyzed for extractable and total elements, NH4-N/NO3-N, electrical conductivity, C/N ratio, humic and fulvic fractions, hydrolytic enzyme activities, radish germination, respiration CO2 and microbiological parameters. The results indicated that humic acid: fulvic acid ratio, total bacteria count, and hydrolytic enzyme activities were sensitive parameters to define compost maturity and more specific tools to explain microbial activity and humification degree along the curing phase. The proposed model could be used to evaluate compost maturity with good reliability. <![CDATA[<b>Effect of Carbon source on dissimilatory nitrate reduction to ammonium in Costal Wetland sediments</b>]]> 15N tracing technique was applied to investigate the effects of various organic carbon (OC) sources on dissimilatory nitrate (NO3-)reduction to ammonium (NH4+) (DNRA) rates in the coastal wetland sediments. Soils collected from the Chongming Dongtan wetland were incubated at 25ºC in the dark for 24 h following the additions of OC sources (glucose, acetate, malate, citrate and oxalate (500 μg C g-1 dry soil)) and 15N-labeled NH4(15)NO3 (initial 15N atom% of NO3--N is 20%). The results showed that soil DNRA rates varied from 0.018-0.497 mg N kg-1 dry soil d-1during the whole incubation, and the rates differed significantly among treatments following the order: oxalate> citrate> glucose> acetate> malate> no exogenous C addition over the first 12-h incubation. This was possibly caused by the different decomposition rates of various OC sources, which further influenced the available energy provided for DNRA microorganisms. Soils with no addition of exogenous C showed lower soil DNRA rates, presumably because of the low C/NO3- ratio as well as energy availability. The relative lower soil DNRA rates over the 24-h incubation indicated that DNRA is a fast process. Our results suggest that DNRA could be controlled by OC sources, especially organic acids, demonstrating that the widespread use of glucose in soil laboratory studies might lead to misleading knowledge on understanding the effects of OC on soil DNRA process. <![CDATA[Phosphorus response and optimum pH ranges of twelve pasture legumes grown in an acid upland New Zealand soil under glasshouse conditions]]> Pasture legumes provide critical nitrogen inputs but fail to persist in typical acidic low P fertility upland soils. Alternative legume species for these environments are urgently sought. Twelve novel legume species were grown for 42 weeks under glasshouse conditions in an acidic upland New Zealand soil. Phosphorus (P) was applied at eight rates (0, 10, 30, 60, 100, 250, 500, 1500 mg kg-1 soil) or lime (100% CaCO3) at five rates (0, 2, 5, 8, 15 t ha-1 equivalent). Annual species grew on average for 25 weeks, while perennial species grew for 42 weeks. Yield was measured and herbage was analysed for macro and micro elements and soils analysed for pH, exchangeable Al and Olsen P. P responses differed substantially between legume species which were likely driven by genetic adaptations to low phosphorus environments. Critical shoot P concentrations for optimum yield were identified and ranged from 0.23 (tagasaste) to 0.39 % P (falcata lucerne). Arrow leaf, subterranean and balansa clovers had the greatest yield increase at low P inputs (100 mg P kg-1) and show promise as alternatives to white clover. Lime treatments increased the yield of all species to a point beyond which yield decreased with further additions. Increased yield was primarily driven by decreased soil exchangeable aluminium (Al) concentrations and to a lesser extent by increased soil P and molybdenum (Mo) availability, while decreases were driven by lower soil P and boron (B) availability at high pH. Thresholds for soil exchangeable Al differed between legume species. Species with higher Al thresholds (7 - 8 mg Al kg-1) were tagasaste, lotus, persian and gland clovers and falcata lucerne. These species show promise for acid soil environments with soil Al issues and should now be investigated further in field experiments. For many of these legume species this represents new and critical information. <![CDATA[<b>Surface application of limestone and calcium-magnesium silicate in a tropical no-tillage system</b>]]> Although lime is currently the most commonly applied material for soil acidity correction in Brazil, calcium-magnesium silicate application may efficiently replace this source due to its higher solubility and silicon supply, which is beneficial for plant development. This study aimed to evaluate the efficiency of surface liming and silicate application on soil chemical attributes as well as soybean and maize nutrition, yield components, and grain yield. The experiment was conducted in a Rhodic Hapludox in Botucatu-SP, Brazil. The randomized complete block design contained 16 replications. Treatments consisted of two materials for soil acidity correction (dolomitic lime, calcium/magnesium silicate), applied on October 2006 to raise base saturation up to 70%, and a control, with no acidity correction. Soybean and maize were sown in 2006/2007 and 2007/2008, respectively. After 18 months Ca-Mg silicate corrected soil acidity up to 0.60 m, and increased exchangeable base levels up to 0.40 m. Silicate increased silicon concentrations in plant tissues in both crops as well as phosphorus in soybean. The application of both sources increased calcium and magnesium concentrations as well as yield components and yield grains of soybean and maize. Soil acidity correction improved the efficiency of fertilizers applied for grain production. <![CDATA[<b>Multi-rotation impacts of increased organic matter removal in planted forests</b>]]> Organic matter cycling is critical to nutrient supply in forested ecosystems. Harvesting influences future nutrient supply by removing organic matter, but the extent of removal varies with harvesting methods. In New Zealand plantations there is little long-term data to help evaluate the relative impact of these methods on the sustainability of site productivity. To explore this issue a modelling study was initiated using the NuBalM platform to simulate the response of forest nitrogen (N) pools and the productivity of Pinus radiata D. Don to the consisten removal of different amounts of organic matter at harvest over multiple 30 year rotations across a range of growth trajectories. The harvesting method involving the greatest amount of organic matter removal (OMR) induced significant reductions in N pools and productivity by the end of the second rotation, while moderate OMR induced reductions by the end of the third rotation. Minimal OMR reduced N pools but not productivity by the end of the fourth rotation. This exploratory work suggests that management practices which influence the amount of organic matter on site can play an important role in long-term productivity and should be considered in further risk based management decision making. <![CDATA[<b>Potential of mycorrhizal inocula to improve growth, nutrition and enzymatic activities in <i>Retama sphaerocarpa</i> compared with chemical fertilization under drought conditions</b>]]> The growth of Retama sphaerocarpa under drought conditions was similarly increased by arbuscular mycorrhizal (AM) colonization [native AM fungal consortium (M), allochthonous Rhizophagus intraradices (RI)] or H3PO4 application [25 ppm P (1P) or 50 ppm P (2P)]. However, the antioxidant ascorbate peroxidase (APX) activity was increased by P-fertilization and decreased by AM colonization in plants of similar size, which revealed possible AM protection against drought. RI was most effective in enhancing P and it also reduced glutathione reductase (GR) activity compared with plants of similar biomass from other treatments. In a subsequent study the mixture of autochthonous inocula (AM fungal consortium (M) plus native Bacillus thuringiensis (B)) were able to fortify K2SO4 fertilization [5 mM K (1K) or 10 mM K (2K)] on R. sphaerocarpa under drought. Dual inocula increased nutrient content only in plants fertilized with 1K, while 2K even decreased the abundance of arbuscules. The reduced superoxide dismutase (SOD) and APX and the elimination of catalase (CAT) and GR activities found in co-inoculated K-fertilized plants suggested the lowest oxidative stress and the highest potential to cope with drought irrespective of nutrition. In both experiments inocula enhanced soil enzymatic activities, which also contributed to higher performance of inoculated plants under drought. <![CDATA[<b>Effect of residue mixtures on response of cumulative respiration to salinity</b>]]> The study aimed to investigate the response of soil respiration to salinity when amended with mixtures of rapidly and slowly decomposable residues. Two incubation experiments were carried out with loam soils having EC(1:5)0.1, 1.0, 2.5 and 3.3 dS m-1. In experiment one, the four soils were amended with 20 g kg-1 soil as sawdust (C/N 114) or kikuyu (C/N 19) alone or mixed at different ratios. In all mixtures, the decrease in cumulative respiration at 1 dS m-1compared to non-saline soil was smaller than with sawdust alone. In experiment two, three soils (EC(1:5)0.1, 1.0 and 2.5 dS m-1) were amended once or three times to a total addition rate of 10 g C kg-l soil either with sawdust alone, kikuyu alone or mixtures. In the treatments with mixtures, the decrease in cumulative respiration from non-saline to EC 1 dS m-1 was smallest in the treatments with three residue additions where 25% kikuyu was added on day 0 or on day 14 after addition of 50% sawdust on day 0. We conclude that even a relatively small proportion of rapidly decomposable residue in a mixture is sufficient to alleviate the negative impact of salinity on soil respiration. <![CDATA[<b>Soil nitrogen contribution to grasslands and its implication for nitrogen use efficiency</b>]]> In pasture systems of southern Chile, nitrogen (N) fertilization is mostly carried out without considering soil N supply, while seasonal N plant uptake is partially accounted for. These aspects are fundamental to correctly decide N fertilization. The aim of this work was to determine soil N contribution to grasslands yield in southern Chile and its implication for N use efficiency. Three treatments were distributed in a completely randomized block design with four replicates. A negative control treatment without N application and a positive control without N deficiency (450 kg N ha-1) were considered. An optimized treatment was also used, so that the total amount of mineral N applied as fertilizer was only that necessary to account for the arithmetic difference among plant uptake and N soil supply, resulting in the application of 171 kg N ha-1 only. Soil mineralization was high (241-934 kg N ha-1) and strongly affected by soil available N (VIP > 0.8). The 450 kg N ha-1 treatment produced 1,726 kg DM more than the 171 kg N ha-1 treatment. Nevertheless, this increase was associated to the application of an extra 279 kg N ha-1, so that the extra yield was produced at a 6 kg DM kg-1N efficiency. This value was one third of that showed by the optimized treatment, which was1.8times more efficient in the use of N than the 450 kg N ha-1 treatment, on average. Results suggest that it is possible to adjust pasture’s N fertilization considering soil N contribution via mineralization, and that this improves resources efficiency while maintaining pasture productivity. <![CDATA[<b>Impact of different tree species on soil phosphorus immediately following grassland afforestation</b>]]> Previous studies have revealed that significant changes in soil phosphorus (P) occurred as a consequence of grassland afforestation, although when these changes occurred and the influence of different tree species remains largely unknown. This study involved assessing changes in soil phosphorus (P) over a 10 year period following the afforestation of grazed pasture with 3 contrasting tree species (Pinus radiata, Cupressus macrocarpa, Eucalyptus nitens) in a replicated field trial at Orton Bradley Park, New Zealand. A combination of techniques (sequential fractionation, alkaline phosphatase hydrolysable P, solution 31P nuclear magnetic resonance spectroscopy) was used to quantify changes in the nature and bioavailability of soil P. Results revealed that the establishment and growth of trees caused a significant decrease in soil organic P within 10 years, indicating net organic P mineralisation. Surprisingly this trend was similar under all three tree species, which suggested similar soil P acquisition despite differences in the type of mycorrhizae associated with each species: P. radiata is ectomycorrhizal, C. macrocarpa is arbuscular mycorrhizal, and E. nitens can be ectomycorrhizal or arbuscular mycorrhizal. The observed changes in soil P dynamics were attributed a combination of tree growth and P uptake irrespective of species and changes in P inputs and organic P turnover associated with the cessation of grazing following tree planting. Changes in the nature of organic P determined 10 years after establishment indicated that organic matter inputs associated with tree growth were having an increasing influence on soil P dynamics with time. <![CDATA[<b>Arbuscular mycorrhizal fungi biodiversity</b>: <b>prospecting in Southern-Central zone of Chile. A review</b>]]> The main factors affecting the diversity of arbuscular mycorrhizal fungi (AMF) are host plant, environmental characteristics and geographical location. A better understanding of the influence of land use changes on AMF abundance will help in improving their management, leading to improved plant productivity in soils, and will also be useful in designing more sustainable agronomic management practices. The aim of this work was to document the occurrence and diversity of AMF species in the Southern Central zone of Chile. This information has been generated by seven separate studies which provide the basis for discussion of the AMF species found in this zone. The work includes a bibliographic review of the records from croplands, grasslands and forests generated by collections made during the period 2004-2014 in Chile. Overall we recorded 21 genera and 66 species of Glomeromycota. This represents 24% of species of AMF known so far. Acaulospora represents 23% of all species and Glomus 20%. It is concluded that more studies are needed in this and other regions of Chile for a more comprehensive knowledge of the AMF diversity in the country. These biodiversity studies will help to define the ecology of these important soil microbiological resources. <![CDATA[Temperature sensitivity of carbon decomposition in soil aggregates along a climatic gradient]]> Global warming affects the carbon (C) pools in terrestrial ecosystems, accelerating biological processes that feed back into the phenomenon of climate change. Globally, grassland ecosystems accumulate large quantities of organic C into soils and are considered a corner stone for global warming mitigation. The aim of this study was to evaluate the temperature sensitivity of C decomposition in different soil aggregate fractions in grassland ecosystems across a north-south latitudinal gradient in Chile. Soil samples were collected from Mediterranean semi-arid (MSA; 32°31, to 34°19, south latitude), temperate semi-oceanic (TSO; 35°36, to 36°27, south latitude), temperate oceanic (TO; 40°36, to 43°03, south latitude) and subpolar semi-oceanic (SPSO; 43°57, to 47°40, south latitude) climate zones, and water-stable macroaggregates (250-2,000 µm) and free microaggregates (50-250 µm) were isolated. Two experiments were performed using short-term incubations (14 days). First, absolute soil respiration and specific soil respiration from isolated aggregates were assessed at 20 °C, and second, the isolated aggregates were incubated at different temperature levels (20-30 ºC for MSA and TSO; 10-20 ºC for TO and SPSO) to quantify the energy of activation (Ea) and temperature sensitivity (Q10). In general, the results do not provide evidence of differences between soil aggregate fractions in any of the evaluated parameters, but the soils differed across the latitudinal gradient. High absolute respiration rates and specific respiration, which were related to high grassland productivity, were observed in soils from TO and SPSO zones. The Q10 values demonstrated a strong positive correlation with annual precipitation, so C decomposition in soils from zones with high precipitation exhibits increased temperature sensitivity. <![CDATA[Assessment of phosphorus status influenced by Al and Fe compounds in volcanic grassland soils]]> Volcanic ash derived soils represent between 50-60% of the total arable land area of southern of Chile, and they are the most important soils for pasture production. In these soils, high phosphorus (P) fixation and, in turn, low P availability and high aluminium (Al) soluble concentrations (at low pH) are the most limiting factors for pasture production. At the same time, the complexes between Al-or iron- (Fe) and organic matter as well as short-range order alumino-silicates (allophane) allow the retention of huge quantities of soil P. The aim of this work was to assess the status of P by both sequential extraction procedure (Hedley) and 31P-NMR analysis as influenced by Al and Fe in volcanic grasslands Andisols (Pemehue, Gorbea, Piedras Negras and Llastuco Soil Series) from Southern Chile. We applied Hedley chemical sequential fractionation to soils in order to examine the potential differences in extractable soil inorganic P (Pi) and organic P (Po) fractions. We also determined total P and Olsen P in these grassland Andisols. Oxalate and pyrophosphate were employed to determine the active and organic matter complexed Al and Fe, respectively. Furthermore, we quantified Al and Fe in extracts of the Hedley P fractions. We found that Al extracted in oxalate was correlated positively with labile Po concentration, specifically with both the NaHCO3-Po(r=0.45, P≤0.01), and the NaOH-Po (r=0.43, P≤0.01) fractions. This observation was reinforced by 31P-NMR analysis that showed higher monoester P and myo-IP6 content in soils with higher amounts of oxalate Al. Hedley sequential fractionation procedure confirmed the role of Al in the NaOH-Po fraction for promoting Po storage, as both fractions were correlated (r=0.33, P≤0.05). In addition, Fe plays a substantial role in recalcitrant P accumulation as we found a high correlation between residual P and oxalate Fe (r=0.55, P≤0.01). <![CDATA[<b>Phosphate solubilization by fungi with nematicidal potential</b>]]> We evaluated the nematicidal potential and phosphate solubilization ability of the fungal species Geomyces pannorum and Paecilomyces carneus, which are associated with the potato cyst nematode Globodera rostochiensis. In a broth medium containing calcium phosphate, the two fungi solubilized between 67%-96% of the insoluble phosphorus that was present in the medium, and in a broth medium containing iron phosphate, the phosphorus that was solubilized by the two fungi ranged between 2%-13%. In a greenhouse experiment, G. pannorum and P. carneus were applied to soil that was naturally infested with G. rostochiensis and planted with Avena sativa. The fungi increased the available phosphorus in the soil by more than 30%, and Paecilomyces carneus also reduced the nematode population by 71%. This study is the first to report on the ability of G. pannorum and P. carneus to increase the available phosphorus in the soil, suggesting that these fungal species may have potential uses in agricultural soils with insoluble phosphorus. Moreover, this study provides a new alternative that contributes to the sustainable management of crops with bio-agents that have dual activity; they increase the available phosphorus in the soil and mitigate plant parasitic nematodes. <![CDATA[Isolation of efficient phosphate solubilizing bacteria capable of enhancing tomato plant growth]]> Phosphorus is one of the three macronutrients that are essential for plant growth and development. Inorganic phosphorus (P), which can make up to 70% of the total P content in soils, can exist in calcium-, aluminum-, or iron-complexed forms that are unavailable for plant use. As a result, mineral phosphorus, P2O5, is often used as a fertilizer to supplement the nutrient for crop growth. To reduce the addition of mineral phosphorus to agricultural soils, research in naturally occurring phosphate-solubilizing microorganisms has been conducted for decades. This study found bacteria that solubilized phosphate at very high rates. The most efficient of the bacteria presented in this paper, Pantoea sp. Pot1, can solubilize tricalcium phosphate (Ca3(PO4)2) at a rate of 956 mgL-1. This bacteria produces a variety of organic acids, including acetic, gluconic, formic, and propionic acids. Greenhouse experiments demonstrated that tomato plants with soil systems inoculated with Pantoea sp. Pot1 incorporated more P and produced much higher biomass weights than those plants without any added bacteria. <![CDATA[<b>Phosphorus acquisition of wheat, pea and narrow-leafed lupin under different P supplies</b>]]> The aim of this study was to compare wheat, pea and narrow-leafed lupin in terms of their ability to acquire P from soil. Two experiments were conducted at the Universidad Austral de Chile. Treatments combined (i) three species (wheat, pea and lupin) and (ii) two rates of P fertilization (0 (P0) and 50 mg P kg-1 (P1)). In Experiment 1 and 2, shoot biomass was affected (P < 0.01) by genotype, P rate and the genotype x P rate interaction. In wheat, pea and lupin P0 reduced this trait by 92, 76 and 41%, respectively, whereas in Experiment 2 these reductions were 86, 58 and 44%, respectively. P1 increased the P uptake of wheat, pea and lupin by 17, 5 and 3 times, respectively. Wheat, pea and lupin showed the highest, intermediate and lowest cumulative root length under P fertilization. The root: shoot ratio and P uptake per unit root length was affected by genotype, P rate and the genotype x P rate interaction. Wheat, pea and lupin showed the highest, intermediate and the lowest root: shoot ratio, respectively. In contrast, wheat and lupin showed the lowest and the highest P uptake per unit root length in both experiments. The present study showed consistent differences between wheat, pea and lupin regarding their sensitivity to P deficiency and the strategies that these species have developed to acquire P from soil. This information could help improve fertilizer management strategies and optimize soil P use. <![CDATA[<b>Effects of zinc fertilizer rate and application method on photosynthetic characteristics and grain yield of summer maize</b>]]> Zinc deficiency is a worldwide nutritional constraint for crop production in many types of soil, particularly in cereals growing in calcareous soil. Two field trials were conducted to study the effects of zinc fertilizer doses and application method on photosynthetic characteristics and grain yield of summer maize, from June to September of 2013, in Xun County (34º40,12” N, 114º32,24”E) and Yuzhou County (33º59,19”N, 113º33,47”E). Optimal Zn fertilizer application (30 kgZnSO4·7H2O hm-2) increased chlorophyll content in leaves, improved photosynthesis, and increased grain yield of summer maize. At 15 kg ZnSO4·7H2O hm-2, grain yield was higher in Xun County and lower in Yuzhou County when the entire amount was applied as basal fertilization as opposed to being split between the basal and foliar fertilization. The opposite result (grain yield lower in Xun County than in Yuzhou County) was obtained at 30 kg ZnSO4·7H2O hm-2. These results have important implications for guiding the rational application of Zn fertilizer and improving the grain yield of summer maize in Henan province.