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In the long-term field trial on an arable dystric Stagnosols, winter wheat (Triticum aestivum L.) grain yield, nitrogen use efficiency (NUE) and nitrate nitrogen (NO₃^--N) in lysimeter water were compared under treatments of 0, 100, 150, 200, 250 and 300 kg/ha of mineral nitrogen (N) during the growth years 1996/97, 1999/00, 2002/03 and 2005/06. Year properties significantly influenced N availability resulting in different responses of grain yield and NUE under variable treatments. Grain yield showed strong significant correlation with the rainfall accumulated from March to May (r = 0.77). In the case of a dry year 2003, winter wheat yield and NUE were adversely influenced by unfavourable climatic conditions. The optimal response of yield and NUE to increasing mineral N rates was found at the amount of 150-200 kg N/ha. Very strong significant correlation between the total amount of leached NO₃^--N and NUE was found for periods 1999/00 and 2005/06 where, in terms of increasing N levels, lower NUE conditioned higher NO₃^--N leaching (r = 0.91 and r = 0.94, respectively). According to the shallow depth of groundwater and installation of drainage systems, there is still a risk of freshwater contamination by nitrates if the N rates higher than 200 kg/ha were applied.

The study should reveal the effects of soil texture and of seed characteristics of oilseed rape (Brassica napus L.) on seed survival in the soil by a burial experiment. Seeds of 58 conventional and new trait accessions (genetically modified and/or with altered seed ingredients) were buried for six months in sandy loam (SL), clay (c) or silty clay loam (SICL) in the seasons 2008/2009 and 2009/2010 in Germany. Between 84-93% (2008/2009) and 64-87% (2009/2010) of the conventional seeds survived in the soil, and so did 41-67% and 8-44% of the new trait seeds. Significantly more seeds were found in C and SICL compared to SL. Seed survival also significantly depended on the genotype, with high and low seed survival in both conventional and new trait accessions. Seed survival rates are probably linked with moisture and oxygen provided by different soils. As soils with good water storage conditions seem to have a higher probability for oilseed rape seeds from harvest losses to survive, other measures such as growing low dormancy varieties and proper soil tillage are especially relevant to avoid volunteers on these soils.

The objective of this study was to analyze the effect of tillage systems and nitrogen fertilization on the grain yield and quality of spring wheat and on selected chemical and biological properties of soil. The first order factor was the tillage system: (1) conventional (CT) - shallow ploughing and harrowing after harvest of the previous crop, and pre-winter ploughing; (2) reduced (RT) - only a cultivator after harvest of the previous crop, and (3) no-tillage (NT) - only Roundup 360 SL herbicide (a.s. glyphosate) after harvest of the previous crop. The second order factor was nitrogen dose: (1) 90 kg N/ha and (2) 150 kg N/ha. Higher yields were demonstrated for spring wheat sown in CT and RT systems, compared to the NT system. In addition, grain yield was increased by a nitrogen dose of 150 kg/ha, compared to 90 kg/ha. Contents of protein and wet gluten in the grain were also increased by the higher nitrogen dose. The RT and NT systems were observed to increase the content of organic C, total N and available phosphorus in the soil, compared to the CT system. They also increased the number and mass of earthworms in the soil, compared to the CT system.

The aim of this work was to compare herbicide efficacy and reduction of weed reproduction after the application of three frequently used soil residual herbicides during pre-emergent (PRE) and early post-emergent (EPOST) application in maize. Plot field trials were carried out in Central Bohemia during two growing seasons (2010 and 2011). Good efficacy (88%, resp. 83%) was found in isoxaflutole + thiencarbazone (ISF + THC) and terbuthylazin + S-metolachlor (TBA + SMC) on Echinochloa crus-galli, especially in PRE application use. Efficacy on Amaranthus retroflexus was 91% at both tested application periods and there were no significant differences between experimental years. Significant differences in A. retroflexus control were recorded among all tested herbicides (ISF + THC > TBA + SMC > pendimethalin (PEM) + dimethenamid (DMA)). No significant differences between PRE and EPOST were recorded in efficacy on Chenopodium album. Significant differences in efficacy on C. album were recorded among all tested herbicides (ISF + THC > TBA + SMC > PEM + DMA). Mercurialis annua was the most tolerant tested weed, which was significantly better controlled at EPOST herbicide application (73%) compared to PRE application (32%). TBA + SMC showed a significantly higher efficacy on M. annua compared with other tested herbicides. Seed production of all tested weeds was strongly effected by weather conditions, which were significant during 2011, when there was higher than average precipitation during May and June. The most seeds were produced by A. retroflexus > C. album > E. crus-galli > M. annua. ISF + THC best reduced seed production of E. crus-galli, A. retroflexus and C. album, especially when applied at PRE. TBA + SMC best reduced seed production of M. annua. Weed competition on untreated control plots caused yield loss by 90%and 47% in 2011 and 2012, respectively, compared to treatments with the highest yield (ISF + THC).

The aim of this work is to evaluate the changes of Mehlich 3 - P, K, Ca and Mg contents in soil during a long-term field experiments with sewage sludge, farmyard manure (FYM) and mineral NPK (NPK) application, compared to the control non-fertilized treatment. The experiment was established at the Humpolec and Suchdol sites (Czech Republic). Potatoes, wheat and barley were grown in crop rotation. Fertilizing system was based on the same nitrogen dose of 330 kg N/ha per one crop rotation. Archive soil samples from the beginning of the experiment (1996) and from the end of each year's crop rotation (1999, 2002, 2005, 2008 and 2011) were analyzed. In spite of the different soil-climatic conditions of the studied sites, very similar tendencies of P, K, Ca and Mg contents changes after the fertilizing systems used were observed in the soil. In case of the same nitrogen dose (330 kg N/ha), sewage sludge appeared to be better source of bioavailable soil phosphorus compared to the farmyard manure and NPK. On the contrary, FYM was a better source of bioavailable potassium and magnesium, despite the lower total magnesium content in FYM. The NPK treatment was the best long-term source of bioavailable potassium.

To investigate the effect of fertilization practice on dissolved organic nitrogen (DON) in aggregates, the study was conducted and involved four fertilization treatments: no fertilizer; mineral fertilizer (MF); pig manure matched with mineral fertilizer (MFP) and crop straw matched with mineral fertilizer (MFR). The results showed that DON content and storage were the highest in > 5 mm aggregates and were the lowest in < 0.25 mm aggregates. Compared with MF, MFP and MFR significantly increased DON contents in > 5 mm by 404.7% and 184.4%. In comparison with MFR, DON content and storage in > 5 mm aggregates for MFP were significantly enhanced by 77.5% and 75.0%. A significantly positive linear correlation relationship between DON content and microbial biomass carbon content was observed in aggregates (R² = 0.84; P < 0.01). The results suggest that pig manure matched with mineral fertilizer is a preferred strategy for retaining DON nutrient due to enhanced microbial biomass in aggregates on sloping upland of purple soil.

The objective of the present study was to evaluate the effect of P, Ca, S, and/or K and/or Mg application at different rates on the botanical composition, herbage yield and its nutritive value in dehesas developed on calcareous soils. In two growing seasons, 2009/10 and 2010/11, five surface-broadcast fertiliser treatments were applied once in autumn. Two grazing periods were simulated by cutting the pasture in mid-spring and late-spring. Treatment K1, with the highest amount of Ca and without K in its composition, provided higher crude protein values in the herbage than controls in 2009/10. When the effect of each nutrient was analysed separately, a strong and highly positive response of Mg application on herbage production was recorded. A surface application of fertilisers containing 25 kg Mg/ha in autumn could increase herbage yield by 40% under the studied conditions. However, Mg was not applied alone, and thus this increase could be due to an effect of Mg by itself or to a synergistic effect between Mg and other nutrients applied. The application of Ca, P and Mg may also favour the production of high-quality forage by yielding a greater cover of legumes and digestible protein.

A study was conducted to investigate the influence of sodicity induced changes in soil physical properties on paddy root growth in the normal agriculture, semi-reclaimed and sodic soils. The root growth (length, length density, biomass and distribution pattern) were unfavourably affected by the soil physical properties (bulk density, soil aggregate stability, available water content, hydraulic conductivity and soil water retention potential) in the case of sodic soil. The microbial biomass carbon, bacterial, fungal population and dehydrogenase activity showed the lower values in the case of sodosol compared to the normal soil. These soil biological properties tend to sustain paddy root growth in normal and semi-reclaimed soils. Principal component analysis revealed that soil physical properties accounted for 98.2% of total variance in root growth. The study revealed that salt stress induces changes in soil physical properties limiting paddy root growth in the salt affected soils. It is important to reclaim sodosols to alleviate salt induced physical stress for optimum paddy root growth.

A long-term experiment was used to evaluate the effects of different nutrient management practices on the distribution of soil organic N fractions and their contribution to N nutrition of a rice-wheat system. Continuous rice-wheat cultivation for 13 years without any fertilization was unable to maintain total soil nitrogen level to its original level and resulted in a decrease at 8.3 mg N/kg/year. Likewise, amino acid N, amino sugar N, ammonia N, hydrolysable unknown N, total hydrolysable N and non-hydrolysable N decreased by 37.2, 29.6, 33.7, 10.4, 26.6 and 20.4%, respectively over their initial status. However, application of inorganic fertilizers alone or in combination with organic manures led to a marked increase in total N and its fractions. The increase in total N with the application of farmyard manure, press mud and green manure along with inorganic fertilizer over treatment with inorganic fertilizer alone was 23.1, 34.4 and 7.0%, respectively. These results imply that integrated use of inorganic fertilizers with organic manures represent a sound practice for sustaining N reserves in soil. On average, amino acid-N, amino sugar-N, ammonia-N and hydrolysable unknown-N constituted about 27.9, 10.7, 28.7 and 32.7% of the total hydrolysable-N, respectively.

Precise field experiments were established at 3 sites with oilseed rape under different soil-climatic conditions in the Czech Republic (Humpolec, Hněvčeves and Uhříněves) in the years 2008-2010. In this experiment, four fertilizing treatments with increasing S rate were evaluated. The contents of bioavailable (S_W), adsorbed (S_ads), occluded (S_ocl), and hydroiodic acid (HI) reducible (S_HI) sulfur were measured. The contents of the fractions within the studied sites in the samples collected before fertilizers application were comparable. The S_W, S_ads a S_ocl contents did not exceed 10 mg S/kg. The S_HI contents differed depending on site and year. Fertilizing using S as CaSO₄ positively influenced the contents of S_W, S_ads, and S_HI in soil. Sulfur fertilizing had also the positive tendencies to increase the winter rape yields but the differences between studied treatments were not statistically significant.

In precise field trials in the CR in the years 2004 and 2005 the effect of site conditions, yellow- and purple-fleshed varieties and fertilization on the content of total polyphenols (TP) in potato tubers was investigated. Comparing four localities, significantly highest TP content (by 5.7 to 13.4% higher than in other localities) was determined in the locality Stachy in both years, which we ascribe to apparently lower temperatures in the vegetation period in this locality of high altitude. In comparison to yellow flesh varieties, in the case of purple flesh Valfi variety TP content higher by 52 to 153% was recorded as the average of both years. As for the group of eight yellow flesh varieties, Karin variety had the highest TP content and showed a significant increase in comparison to Agria, Saturna and Asterix varieties by 67, 60 and 37%, respectively. TP content was not demonstrably affected by fertilization with mineral fertilizers, but we recorded a tendency to lesser TP content (by 3 to 9.9%) in the variant with higher potassium and magnesium fertilization (166 kg K/ha and 60 kg Mg/ha).

In 2004-2009, a small-plot trial was conducted on permanent grassland dominated by Festuca arundinacea Schreb. on the mesohygrophytic site in order to evaluate effects of four levels of nutrition: F₁ = without NPK fertilization, F₂ = P₃₀ + K₆₀, F₃ = N90 + P₃₀ + K₆₀, F₄ = N₁₈₀ + P₃₀ + K₆₀ kg/ha), four levels of cutting intensity (I₁-4, I₂-3, I₃-2, early, I₄-2, late cut) and their interactive influence, i.e. a total of 16 variants on the production of forage dry matter, production of crude protein (CD) and net energy of lactation (NEL) per hectare. The dominant influence of N-nutrition is documented by significant differences in forage dry matter (DM) production between the variants (with the exception of F₁/F₂) ranging from 4.41-4.80 to 8.44-9.83 t/ha. The effect of different exploitation level on the production is subdominant and no significant differences were found either in the production of forage DM(I₁-6.41 - I₂-6.59 - I₃-6.97 - I₄-7.50 t/ha) or in the production of nutrients. Management models to be recommended for the given type of sward with respect to the interactive influence, efficacy of forage production and quality are as follows: (a) three cuts/180 kg N + PK/ha with forage suitable for dairy cows; (b) two cuts/90 kg N + PK/ha with forage suitable for cattle breeds kept for meat.

Cattle slurry is frequently used fertilizer on grasslands, but little is known about its effect on plant species composition. The aim of this study was therefore to assess effect of different application rates of cattle slurry (S0 - 0, S1 - 60, S2 - 120, S3 - 180, S4 - 240 kg N/ha/year) on the plant species composition of three-cut grassland. The study was performed over 6 years on moderately moist upland Arrhenatherion grassland in the Czech Republic dominated by Alopecurus pratensis, Trisetum flavescens, and Poa spp. Species composition recorded in treatments with application of cattle slurry in rate up to 120 kg N/ha/year was similar to the unfertilized control. During first three years, species richness was similar in all treatments and then decreased the most in S4 followed by S3 treatment. Cover of short forbs increased in S0 and decreased with an increase in slurry application rate which supported tall grasses. Application of cattle slurry up to 120 kg N/ha/year can be considered as suitable compromise between maintenance of species rich grasslands and requirements of farmers for sufficient forage production.

Little attention has been paid to the effect of long-term fertilizer application on concentrations of elements in grain of barley produced on the metal non-contaminated agricultural soil. In 2010, we analyzed yield and concentrations of elements in grain of spring barley in unfertilized control, mineral fertilizer application (N₄P₂K₂ - 70, 60 and100 kg N, P and K per ha) and combinations of farmyard manure or poultry litter with mineral fertilizer (FMN₄P₂K₂ and PLN₄P₂K₂) treatments in the Ruzyně Fertilizer Experiment established on Luvisol in 1955 in Prague (Czech Republic). The yield of grain ranged from 4.03 to 9.74 t/ha in the control and FMN₄P₂K₂ treatment. There was a positive effect of fertilizer application on concentrations of nitrogen, phosphorusand potassium, but no effect on concentrations of calcium and magnesium. With the exception of iron, concentrations of micro (copper and zinc) and risk elements (arsenic, cadmium, chromium, lead, manganese and nickel) were not significantly affected by the fertilizer treatments. Long-term use of organic and mineral fertilizers with appropriate application rates does not represent any risk for contamination of barley grain by risk elements on mineral rich and metal non-contaminated agricultural soils.

Combined application of organic and inorganic amendments was known to play a significant role in improvement of soil properties. A field experiment was conducted to explore the effects of gypsum, farmyard manure and commercial humic acid application on the amelioration of salt affected (saline sodic) soil. During this study, soil pH, electrical conductivity, sodium adsorption ratio, responses of root length and rice paddy yield were examined. Application of gypsum with or without farm manure and commercial humic acid decreased soil pH (8.26%), electrical conductivity (from 6.35 dS/m to 2.65 dS/m) and sodium adsorption ratio (from 26.56 to 11.60), and increased root length (from 9.17 cm to 22.6 cm) and paddy yield (from 695.7 kg/ha to 1644 kg/ha). A negative but significant correlation was observed between root length and electrical conductivity, sodium adsorption ratio (r = -0.93; -0.94, respectively, P ≤ 0.05), whereas positive and significant correlation with paddy yield (r = 0.96; P ≤ 0.05).

Fertilization of crops with pig manure is a common practice throughout the world. Nevertheless, due to the relatively high copper (Cu) and zinc (Zn) contents in pig manure, continuous application of pig manure could have negative effects on soil and plant. The study aimed at the impacts of long-term applying different pig manure rates (equivalently 0, 100, 250 and 500 kg total N/ha/year from 2002 to 2008 and 0, 10, 25 and 50 t fresh weight/ha/year from 2009 to 2011, respectively) on Cu and Zn accumulation in soil and plant. During the 10 years of the experiment, a total of 2.04 to 10.20 kg/ha/year for Cu, 3.15 to 15.73 kg/ha/year for Zn were applied to the soil. Results from this study showed that long-term pig manure application resulted in serious accumulation of Cu and Zn in soil, total Cu and Zn concentrations increased by 204% and 107% at high application rates, respectively. Although topsoil Cu and Zn concentrations were below concentrations considered phytotoxic to crops, according to current Chinese legislation, it would take only less time than 16 and 27 years of high application rates to reach the allowable limits. Our result also suggested that Cu and Zn leaching occurred in the tested soil. The Cu and Zn concentrations in stalks and grains were not affected by the application of pig manure, and these values were lower than the threshold values for animal and human ingestion.

Root net primary productivity (RNPP) was assessed in the wet submontane meadow in the highland region of the Czech Republic. RNPP was studied from 1992 to 1995 with help of the in-growth core technique. The effect of different intensities of fertilization on root growth was covered. In comparison with unfertilized stands, the application of fertilizers (90 kg N/ha) resulted, mostly significantly, in greater root productivity (297 g/m²/year and 2.08 g/m²/day, on average). This represented an increase by 72% and 71%, respectively. Variability in the fraction of RNPP to total net primary productivity was examined. Results indicate that this fraction varied from 0.18 to 0.25 across the compared treatments and decreased with increasing fertilization. Data show how different roles can grasslands play in accumulation of plant matter due to different levels of fertilization.

Plant's nitrogen (N) requirement that is not fulfilled by available N in soil has to be supplied externally through chemical fertilizers. A reliable estimate of soil N-supplying capacity (NSC) is therefore essential for efficient fertilizer use. In this study involving a pot experiment with twenty acidic soils varying widely in properties, we evaluated six chemical indices of soil N-availability viz. organic carbon (C_org), total N (N_tot), acid and alkaline-KMnO₄ extractable-N, hot KCl extractable-N (KCl-N) and phosphate-borate buffer extractable-N (PBB-N), based on their strength of correlation with available-N values obtained through aerobic incubation (AI-N) and anaerobic incubation (ANI-N), and also with the dry matter yield (DMY), N percentage and plant (maize) N uptake (PNU). In general, the soils showed large variability in NSC as indicated by variability in PNU which ranged from 598 to 1026 mg/pot. Correlations of the N-availability indices with AI-N and ANI-N decreased in the order: PBB-N (r = 0.784** and 0.901**) > KCl-N (r = 0.773** and 0.743**) > acid KMnO₄-N (r = 0.575** and 0.651**) ≥ C_org (r = 0.591** and 0.531**) ≥ alkaline KMnO₄-N (r = 0.394** and 0.548**) > N_tot (r = 0.297** and 0.273*). Of all the indices evaluated, PBB-N showed the best correlations with plant parameters as well (r = 0.790** and 0.793** for DMY and PNU, respectively). Based on the highest correlations of PBB-N with biological indices as well as plant responses, we propose PBB-N as an appropriate index of N-availability in the acidic soils of India and other regions with similar soils.

To investigate the environmental advantages of using grass-clover binary mixtures over pure stands as winter cover crops, a serial of five field experiments (each designed as randomized complete blocks with four replicates) was carried out in eastern Slovenia. Trifolium incarnatum L. and Lolium multiflorum Lam. were sown in late summer as pure stands and binary mixtures. Pooled data calculated from all the experiments revealed that the soil mineral N in spring and accumulation of N by plants decreased with decreasing proportion of T. incarnatum in the binary mixtures, while the C:N ratio of cover crop organic matter increased. C accumulation was the highest when the seeding ratio of the binary mixture of T. incarnatum and L. multiflorum was 50:50. In the C and N environmentally sustainable management efficiency coefficients, three important traits of winter cover crops for environmental pro-tection were given equal importance (low soil mineral N content in spring, high C accumulation in plants, and high N accumulation in plants). The coefficient was higher for binary mixtures of T. incarnatum and L. multiflorum than for pure stands of these crops, proving the complex environmental advantages of binary mixtures over pure stands.

Soil samples were collected at both jointing and maturing stages of maize and wheat to compare the effects of 4-year no-tillage (NT) and conventional tillage (CT) on seasonal variations of microbial biomass carbon (C), metabolic quotient, and invertase activity in a sandy loam soil in North China. Soil invertase activity significantly increased (P < 0.05) from summer to spring of the next year and then significantly decreased (P < 0.05) from spring to summer. With a delay of about 3 months, soil microbial biomass C and basal respiration altered in a similar pattern, while microbial metabolic quotient changed on the contrary. Compared with CT, the NT practice significantly increased (P < 0.05) soil organic C content, and tended to result in higher soil microbial biomass C and invertase activity, as well as lower soil microbial metabolic quotient, especially at the jointing stage of maize. Our results indicated that NT might play an important role in the improvement of soil microbial efficiency, especially at the maize seedling season.

A field study was conducted to ascertain the effect of three zinc (Zn) levels: 0, 20 kg ZnSO₄/ha and 20 kg ZnSO₄/ha + foliar spray of 0.5% ZnSO₄, on wheat grain Zn content and factors contributing to or hindering in its bioavailability. Increasing Zn levels were established as serviceable in improving the nutritional status of genotypes. Soil application + foliar spray proved to be paramount for all the traits leading to an 80% increase in grain Zn content, 61.3% in methionine content and a decrease of 23.2% in phytic acid as an average of all genotypes and both years. The genotype UP 2382 was found more suited to Zn fertilization in allocating Zn and maintaining a lower phytate to Zn molar ratio.

To investigate the effects of returning wheat straw to croplands on soil compaction and nutrient availability, this trial was designed: (1) planted crops without fertilization (NF); (2) natural land without human activities (CT); (3) applied mineral fertilizers in combination with 7500 kg/ha wheat straw (WS-NPK); (4) applied mineral fertilizers in combination with 3750 kg/ha wheat straw (1/2WS-NPK); and (5) applied mineral fertilizers alone (NPK). It is found that, compared with NPK, the soil bulk density in 1/2WS-NPK and WS-NPK both decreased by more than 10% in the 0 cm to 15 cm layer, and by 6.93% and 9.14% in the 15 cm to 20 cm, respectively. Furthermore, in contrast to NPK, the soil available nitrogen in the 0 cm to 25 cm layer in 1/2WS-NPK and WS-NPK were higher by 17.43% and 35.19%, and the soil available potassium were higher by 7.66% and 17.47%, respectively. For soil available phosphorus in the depth of 5 cm to 25 cm, it was higher by 18.51% in 1/2WS-NPK and by 56.97% in WS-NPK, respectively. Therefore, returning wheat straw to croplands effectively improves soil compaction and nutrients availability, and the improvement in soil nitrogen and phosphorus availability is closely related to the amount of wheat straw.

A litterbag experiment was conducted to investigate the changes of tannins and nutrients in branchlets at different decomposition stages of Casuarina equisetifolia in southern subtropical coastal zone, China, using the colorimetric assays. The time required for the loss of half of the initial dry weight (t₅₀) was 9.13 months. Total phenolics (TP), extractable condensed tannins (ECT), protein-bound condensed tannins (PBCT), total condensed tannins (TCT) and protein precipitation capacity (PPC) of branchlets litter decreased rapidly, while fibre-bound condensed tannins (FBCT) increased during decomposition. Nitrogen and phosphorus concentration of the branchlet litter both increased gradually during decay. Negative correlations between TP and nitrogen or phosphorus, as well as TCT and nitrogen or phosphorus were found. These chemical changes enhanced the current knowledge on the potential ecological role of nutrient transformation in tannins in C. equisetifolia plantations.

To investigate the effect of low soil pH caused by fertilization on soil available zinc in calcareous soil, this study was conducted based on a long-term experiment consisting of: (a) no fertilization (CT); (b) mineral fertilizer application coupled with 7500 kg/ha of wheat straw (WS-NPK); (c) mineral fertilizer application coupled with 3750 kg/ha of wheat straw (1/2WS-NPK); (d) mineral fertilizer application alone (NPK). Long-term fertilization results in a significant increase in soil DTPA-extractable zinc. However, the increased soil DTPA-extractable zinc is unavailable to crops and mainly confined to 0.25 mm > and 0.25 mm to 1 mm aggregates. Compared to CT, soil DTPA-extractable zinc under fertilization is more than 9.67% and 122.36% higher in 0.25 mm > and 0.25 mm to 1 mm aggregates, respectively. Furthermore, plant-available zinc in the 0-15 cm soil layer and wheat grain zinc are both significantly positive related to soil DTPA-extractable zinc in > 2 mm aggregates. Therefore, plant-available zinc in the 0-15 cm layer is closely associated with DTPA-extractable zinc in > 2 mm aggregates, and the low soil pH caused by long-term fertilization could not enhance plant-available zinc in the surface soil layer nor elevate wheat grain zinc concentration because of the occlusive effect of soil aggregates.

The research results have shown that the enzyme pH index (0.49-0.83) confirmed the neutral or alkaline nature of the soils. Neither the changes in the content of available phosphorus nor in the activity of dehydrogenases, catalase, alkaline and acid phosphatase in soil were due to the factors triggering soil salinity; they were a result of the naturally high content of carbon of organic compounds, which was statistically verified with the analysis of correlation between the parameters. There were recorded highly significant values of the coefficients of correlation between the content of available phosphorus in soil and the activity of alkaline (r = 0.96; P < 0.05) and acid phosphatase (r = 0.91; P < 0.05) as well as dehydrogenase (r = 0.90; P < 0.05). To sum up, one can state that Mollic Gleysols in Inowrocław are the soils undergoing seasonal salinity; however, a high content of ions responsible for salinity is balanced with a high content of organic carbon, humus, phosphorus and calcium directly affecting the fertility of the soils analyzed. The activity of the enzymes depended on the natural content of carbon of organic compounds and not on the factors affecting the soil salinity, which points to the potential of such tests for soil environment monitoring.

Subsoil compaction can result in unfavourable soil physical conditions and hinder the root growth of maize. The effects of deep tillage and conventional tillage on soil physical properties and root growth of maize were studied during 2010-2011 at two sites (loam at Hebi and clay at Luohe) in central China. The results showed that soil penetration resistance, bulk density, water content and root length density were significantly affected by tillage, soil depth and year. Deep tillage had lower penetration resistance and lower soil bulk density, but higher soil water content than conventional tillage across years and depths. Averaged over the whole soil profile, deep tillage not only significantly decreased penetration resistance and soil bulk density, but significantly increased soil water content and root length density on loam, while deep tillage only significantly increased the root length density on clay. We conclude that deep tillage on the loam is more suitable for the root growth of summer maize.

The effects of phosphorus (P) fertilizer on P loss potential, soil Olsen-P and neutral phosphatase activities in paddy soils fertilized with superphosphate or pig manure (PM) were evaluated in this paper. Data were collected from a field experiment in the Tai Lake Basin, China. Superphosphate rates were 0, 17.5, 26.7, and 35.0 kg P/ha, and PM rates were 0, 1.4, 2.1, and 2.8 t/ha for each crop, respectively. Soil Olsen-P in the plow layer increased to a greater extent with PM than with superphosphate. Pig manure increased neutral phosphatase activities in the plow layer compared with PM-free treatment. In contrast, superphosphate inhibited neutral phosphatase activities compared with superphosphate-free treatment. Spring application of P fertilizer markedly increased the total P of surface water in November (< 0.01 vs. 0.10 mg/L) compared with P-free treatment. The total P of shallow groundwater at a 75 cm depth was ~0.01 mg/L. Phosphorus fertilizer did not influence Olsen-P or neutral phosphatase activities under the plow layer. Downward movement of P did not occur. Appropriate rate of P application of 26.2 kg P/ha for each crop in this soil reduced the risk of P loss in the paddy wetland ecosystem.

A field experiment was conducted in 2008-2010 at the Experimental Station of the Faculty of Agricultural Sciences in Zamość (50°42'N, 23°16'E), University of Life Sciences in Lublin. The aim of the study was to assess the impact of cropping method and weed control methods on the content of Cu, Zn, Fe and Mn in maize and on their uptake. Two cropping methods were studied - sole cropping and strip cropping (common bean, dent maize and spring barley in adjacent strips) and two weed control methods - mechanical and chemical. Strip cropping reduced Mn content in maize, did not significantly affect Zn content, and increased accumulation of Cu and Fe. The content and uptake of the elements by maize depended on the position of the row in the strip and on the adjacent plant species. Placement next to beans resulted in higher Fe and Zn content, while placement next to barley increased Cu content. The highest Mn content was noted in maize from the centre row. In general, micronutrient uptake by maize was lowest in the middle row. These results indicate that strip cropping can be an effective agricultural practise for plant biofortification.