Low Fertilizer Treatment Research Articles

Electrical signal of pepper during cropping period affected by different amount of fertilizer

Precision agriculture requires supply of adequate amount of fertilizer application to increase crop yield and prevent environmental contamination. Objective of the study was to evaluate response of pepper under different fertigation method and amount using plant induced electrical signal (PIES) for precision agriculture. Pepper was fertigated 10 times with recommended additional nitrogen fertilizer and set as a control. Low fertilizer treatment did not receive additional urea and high fertilizer received three times higher amount of nitrogen fertilizer. Conventional treatment was fertigated as basal fertilizer and once with additional fertilizer. The PIES decreased during vegetative stage and remained constant at reproductive stage because of reduced nutrient and water uptake. The PIES showed positive relationship with soil NH4+, NO3−, stem NO3− and leaf N, which resulted in highest PIES value during reproductive stage in high fertilizer treated pepper. Plant growth parameters were also related with the PIES although yield was not affected by different fertilizer treatment.

Residual Carbon Derived from Different Maize Parts Differed in Soil Organic Carbon Fractions as Affected by Soil Fertility

Maize straw returning is one of the important measures to improve dryland soil organic carbon (SOC). However, the effects of different maize parts on SOC fractions with different soil fertility levels in situ are not exactly clear. Therefore, an in situ field incubation experiment over 540 days, by adding different 13C-labeled maize parts (root, stem and leaf) into low- (no fertilizer treatment) and high- (manure treatment) fertility soils, was conducted at a long-term brown earth experimental site in Shenyang of China to figure out the effects of different maize parts on SOC fractions (dissolved organic carbon (DOC) and particulate organic carbon (POC)). The results showed that the distribution–DOC ratio of low-fertility treatment was higher than that of high-fertility treatment in the period of rapid decomposition of straw. In both low- and high-fertility soils, the ratio of carbon to DOC in leaf residue was higher than that in root and stem residues. The proportion of root, stem and leaf residue converted to DOC in low-fertility soil was 4.51%, 3.89% and 5.00%, respectively. The proportion of root, stem and leaf residue converted to DOC in high-fertility soil was 4.10%, 3.65% and 4.11%, respectively. As for the distribution–POC ratio, during the period of rapid decomposition of straw, the ratio of carbon conversion from root and stem residue to POC was generally higher than that from leaf residue. The ratio of carbon conversion to POC of root, stem and leaf residues in high-fertility treatment was higher than that in low-fertility treatment. In low-fertility treatment, the proportion of root, stem and leaf residues converted to POC was 41.34%, 46.33% and 36.11%, respectively. The proportion of root, stem and leaf residue converted to POC in high-fertility soil was 46.48%, 44.45% and 41.14%, respectively. The results showed that, for DOC, a low fertility level and more leaf residue types were beneficial. While, for POC, root and stem residues with a high fertility level were beneficial. These results provide evidence that the addition of different parts of maize residues would have differing effects on DOC and POC. Leaf residues in low-fertility soils were more suitable for increasing DOC. Root and stem residues in high-fertility soils were more suitable for increasing POC. Nevertheless, we could not ignore the unmeasured SOC fractions that some of the residues could be converted to.

The transcriptomic response of bovine uterine tissue is altered in response to sperm from high- and low-fertility bulls†.

Despite stringent quality control checks, some bulls with apparently normal semen quality yield lower than expected pregnancy rates. This study profiled the transcriptome and performed histological analysis of the bovine uterus in response to sperm from high-fertility (HF) and low-fertility (LF) bulls. Postmortem uterine biopsies and uterine explants were collected from heifers 12h after a fixed time artificial insemination (AI) to a synchronized estrus with frozen-thawed semen from five HF (fertility rate 4.01% ± 0.25) and five LF (fertility rate - 11.29% ± 1.11; mean ± SEM) bulls. Uterine biopsies were also collected from control (CTRL) heifers, which were not inseminated. RNA-sequencing and histological analysis were performed for differential gene expression and neutrophil quantification. In the HF treatment relative to CTRL heifers, there were 376 genes significantly differentially expressed in the endometrium with just one gene differentially expressed in the LF treatment relative to CTRL heifers. Comparing the HF and LF treatments directly, there were 40 significantly differentially expressed genes (P < 0.05). Transcriptomic analysis shows a predominant role for the inflammatory marker Interleukin-1 alpha, which was further confirmed by immunohistochemistry. Quantification of neutrophils in the endometrium showed a significant effect of sperm; however, there was no difference in neutrophil numbers between HF and LF groups. In conclusion, this novel study clearly shows a distinct inflammatory response to sperm in the endometrium and a divergent transcriptomic response to semen from HF and LF bulls.

Source–Sink Balance Optimization Depends on Soil Nitrogen Condition So as to Increase Rice Yield and N Use Efficiency

Genetic improvement has been devoted to increasing rice yield by increasing the spikelet number per panicle and the spikelet/leaf ratio. As a result, indica-japonica hybrid rice “Yongyou” varieties with large panicles and superhigh yield potential have been developed. These varieties exhibit significantly higher grain yield and nitrogen use efficiency for grain (NUEg) under moderate and high N supply conditions due to their large sink size, but their yield performance remains obscure under low N input and low soil fertility conditions. In the present study, we investigated four varieties including Yongyou2640 (YY2640, large-panicle india-japonica hybrid variety), Yangliangyou6 (YLY6, two-line indica hybrid variety), Quanyou6 (QY6, three-line indica hybrid variety), and Huanghuazhan (HHZ, indica inbred variety) under two low soil fertility treatments [LF (removing half of soil depth) and CK] and two N fertilizer rates (0 and 100 kg N ha−1) in Central China. The results showed that the grain yield of YY2640 was more responsive to fertility than that of other varieties, which was 19.4–42.3% higher than that of the other three varieties under CK N100 treatment, but it was 14.5–19.4% lower than that of YLY6 and QY6 under LF N0 and LF N100. A higher spikelet/leaf ratio resulted in more biomass and N partition to panicles rather than to leaves under LF N0 and N100. Slightly more post-flowering dry matter obtained from higher leaf N content and crop growth rate failed to compensate for the adverse effects of reduced pre-flowering dry matter accumulation and stem-to-grain translocation during grain filling. This led to the lower NUEg of YY2640 than YLY6 and QY6 under low soil fertility conditions. Based on these findings, the present study suggested that the source–sink relationship of the super hybrid varieties should be optimized according to the soil N supply condition.

Differential accumulation patterns of microbial necromass induced by maize root vs. shoot residue addition in agricultural Alfisols

Soil organic carbon (SOC) has significant implications in regulating soil health. Emerging insights emphasize the important role of microbial anabolism in SOC storage by continuously transforming plant fragments into persistent microbial residues. However, knowledge of the sequestration pathway of root versus shoot carbon (C) is under debate. While recent studies have shown that labile shoot residue is disproportionately important for stable SOC accumulation through microbial assimilation, how plant root vs. shoot residue retention impacts microbial-derived C under different soil fertility conditions remains elusive. Here, we conducted a 500-d in situ experiment using Alfisols with low fertility (LF) and high fertility (HF) amended with maize root or shoot (both stem and leaf) residues. The microbial residues (amino sugar biomarkers) and microbial communities (lipid biomarkers) were analyzed at 60, 90, 150, and 500 d after the amended materials were added. The results showed that shoot residue input facilitated microbial residue accumulation more efficiently than root input before 150 d. However, at the end of the experiment, the treatment containing added root residue accumulated more microbial residues and produced a higher proportion of microbial residue in SOC, compared with shoot treatment. These results provide novel evidence that root residue can also yield SOC efficiently through the organic substrate–microbial anabolism pathway, but it depends on the decomposition period. Moreover, soil fertility plays an important role in regulating the quantity and relative composition of microbial residues. Specifically, crop residue application greatly increased the contribution of microbial residue C to SOC in the LF treatment compared to that in the HF treatment on day 500. Meanwhile, crop residue addition had a more positive effect on fungal residue accumulation in the LF soil, while it facilitated the accumulation of bacterial residue in the HF soil. These findings highlight that crop residue addition (especially root residue) is an effective approach for improving microbial-derived C sequestration in infertile soils.

Species identities impact the responses of intensity and importance of competition to the soil fertility changes

How plant competition varies with the changes of biotic and abiotic factors has been debated for a long time in the field of ecology. The aim of this study was to explore how neighbors and soil fertility influenced the intensity and importance of competition on species Stipa grandis and S. krylovii. We conducted a target species (S. grandis and S. krylovii) × soil fertility (low and high fertility) × competition treatment (4 treatments: two target species grown in monoculture and in mixture with each other, and in mixture with Leymus chinensis or Agropyron cristatum) microcosm experiment. We calculated the intensity (NIntA) and importance (NImpA) of neighbor-effect with additive symmetry for each target species under different treatments, and explored how the NIntA and NImpA were influenced by the target species, neighbor identity and soil fertility. We calculated the fertilizer-addition effect index on each target species to explore how neighbor identity influenced the index. (1) When target species in mixture with L. chinensis, both the NIntA and NImpA decreased with the increase of soil fertility. The NImpA was significantly negative on S. grandis under both soil fertility treatments and on S. krylovii under the high soil fertility treatment. (2) When target species in mixture with A. cristatum, the NIntA significantly influenced by the interaction between target species and soil fertility. The NImpA was significantly negative on S. grandis under the low soil fertility treatment and on S. krylovii under the high soil fertility treatment. (3) When in S. grandis – S. krylovii mixture system, the NIntA increased with the increase of soil fertility, and the NImpA showed no significant effects on each target species. (4) The fertilizer-addition effect was higher than zero for all treatments except the one on S. grandis in mixture with L. chinensis. The effect on S. krylovii was relatively lower than that on S. grandis in mixture with A. cristatum but was relatively higher in any of the other three competition treatments. The present findings demonstrated that the identities of both target and neighbor species influenced the fertilizer-addition effect and the responses of intensity and importance of competition to the changes of soil fertility. The present study showed the complexity of target species and neighbor identities in influencing the outcomes of plant competition, and provided novel insights into how plant competition driving the community dynamics in the context of soil fertility changes.

Soil fertilization affects the abundance and distribution of carbon and nitrogen cycling genes in the maize rhizosphere

Soil microbes perform important functions in nitrogen and carbon cycling in the biosphere. Microbial communities in the rhizosphere enhance plants’ health and promote nutrient turnover and cycling in the soil. In this study, we evaluated the effects of soil fertilization with organic and inorganic fertilizers on the abundances and distribution of carbon and nitrogen cycling genes within the rhizosphere of maize plants. Our result showed that maize plants through rhizosphere effects selected and enriched the same functional genes glnA, gltB, gudB involved in nitrogen cycle as do high compost and low inorganic fertilizer treatments. This observation was significantly different from those of high doses of inorganic fertilizer and low compost manure treated soil. Only alpha amylase encoding genes were selectively enriched by low compost and high inorganic fertilized soil. The other treatments only selected xynB (in Cp8), lacZ (Cp4), bglA, pldB, trpA (N2), uidA (N1) and glgC, vanA (Cn0) carbon cycling genes in the rhizosphere of maize. Also Actinomycetales are selected by high compost, low inorganic fertilizer and control. The control was without any fertilization and the soil was planted with maize. Bacillales are also promoted by low compost and high inorganic fertilizer. This indicated that only microbes capable of tolerating the stress of high dose of inorganic fertilizer will thrive under such condition. Therefore, soil fertilization lowers nitrogen gas emission as seen with the high abundance of nitrogen assimilation genes or microbial anabolic genes, but increases carbon dioxide evolution in the agricultural soil by promoting the abundance of catabolic genes involve in carbon cycling.

Effects of whole soil-plastic mulching system and fertilization rates on water consumption characteristics and yield of tartary buckwheat in arid land

<p indent=0mm>In order to study the effects of whole soil-plastic mulching planting and different fertilization rates on soil water consumption characteristics and yields of tartary buckwheat, a three-year (2015–2017) located experiment was carried out in semi-arid region of east-central Gansu Province, China, under whole soil-plastic mulching planting system. Four fertilization treatments under soil-plastic mulching were accordingly designed, including high application rate (HF, N <sc>120 kg</sc> hm^–2 + P₂O₅ <sc>90 kg</sc> hm^–2 + K₂O <sc>60 kg</sc> hm^–2), medium rate (MF, N <sc>80 kg</sc> hm^–2 + P₂O₅ <sc>60 kg</sc> hm^–2 + K₂O <sc>40 kg</sc> hm^–2), low rate (LF, N <sc>40 kg</sc> hm^–2 + P₂O₅ <sc>30 kg</sc> hm^–2 + K₂O <sc>20 kg</sc> hm^–2), and zero fertilization rate (ZF), whereas ZF with traditional non-mulching planting was set as the control (CK) to illustrate the effects of soil-plastic mulching and fertilization on water consumption characteristics, yields and water use efficiency (WUE) of tartary buckwheat in semi-arid area of China. The results showed that the effects of rainwater collection and soil moisture conservation were obvious after planting tartary buckwheat with whole soil-plastic mulching, which also improved soil water environment and increased pre-anthesis soil water storage (SWS, mm). LF was able to regulate soil water consumption before and after anthesis stage according to different precipitation years and soil moisture conditions. Compared with ZF, MF, HF, and CK in dry years, LF improved post-anthesis SWS by <sc>2.8–23.5 mm</sc> and increased crop pre-anthesis water consumption in the <sc>0–100 mm</sc> soil profile by <sc>26.3–32.4 mm</sc> in tartary buckwheat. As a result, LF increased total crop water consumption in the whole growth period by <sc>44.5 mm,</sc> and boosted water consumption module coefficient and intensity. Moreover, compared with ZF, MF, HF and CK, LF treatment increased dry matter weight at maturity stage by 1.2%–58.8%, leaf area index (LAI) at filling stage by 4.1%–68.5%, grain weight per plant by 1.6%–61.6%, plumpness rate by 0.6%–29.2%, biomass yield by 1.1%–182.5%, grain yield by 1.1%–130.4%, and water use efficiency (WUE, kg hm^–2 mm^–1) by 0.3%–102.7%, respectively. In conclusion, the storage effect of low amount fertilizer treatment for tartary buckwheat planting with whole soil-plastic mulching in dry land was obvious, which could achieve the coupling effects of soil moisture and fertilizer and regulate crop water consumption according to the environmental conditions such as precipitation during crop growth period, and it could significantly improve the biomass yield, grain yield and WUE of tartary buckwheat. Therefore, it was a suitable cultivation mode for yield-increasing and efficiency-boosting of tartary buckwheat in semi-arid area.

Effect of soil fertility on the allocation of nitrogen derived from different maize residue parts in the soil-plant system

Crop residue incorporation is an effective agricultural management to enhance soil organic carbon and nitrogen (N) sequestration, which inevitably affects the crop N uptake, and consequently the allocation of N in the soil-plant system. However, to what extent the crop residue type and soil fertility moderate the contribution and recovery of maize (Zea mays. L) residue-derived N (residue-N) in the soil-plant system is poorly understood. Therefore, a 2-year in situ experiment was conducted on an Alfisol with high fertility (HF) and low fertility (LF), along with the application of 15N-labeled maize root or straw (both stem and leaf) residues. The results showed that the HF treatment had a smaller proportion of residue-N in total N uptake compared with the LF treatment (on average of 2.0% vs. 3.6%), but with a larger recovery rate (on average of 23.5% vs. 12.8%). The application of straw residues increased the proportion of residue-N in plant total N compared with that from the application of root residues in the HF treatment. The percentage of residue-N in total soil N (TSN) and the residue-N recovery in the LF soil were 60.7–108.5% and 9.6–25.8% higher than those in the HF soil, respectively. The proportion of root-derived N (root-N) in TSN was significantly higher than that of straw-derived N (straw-N) in the LF soil. In addition, total residue-N recovery rates were similar among all residue-amended treatments. The results indicated that the soil with high fertility could increase residue-N utilization by plant, especially the straw-N, while the soil with low fertility favored the accumulation of the residue-N in soil, especially the root-N, and its low fertility was more likely to be improved. Overall, soil fertility and residue type could significantly affect the allocation of maize residue-N in the soil-plant system.

Soil property and cotton productivity changes with nutrient input intensity in the Taklimakan desert of China

Conversion of native desert into irrigated cropland is common in southern Taklimakan desert of China though the effect on soil fertility are not well understood. This study examined the effect of cultivation intensity on soil properties and crop productivity using 9-year data from cotton grown at three intensities of no fertilizer, low, and high fertilizer inputs. A native desert with sparse vegetation of Alhagi sparsifolia Shap. was used as a check. Treatment effects on soil properties fluctuated during 2005–2009 due to mineralization of applied manure or weather variation, and kept stable during 2010–2013. Soil organic carbon (SOC) during 2010–2013 increased with intensity, being 1.0–2.4 times greater in the fertilized than unfertilized cotton and desert. Soil total N, plant available N, and P content increased with fertilizer inputs. Available N content in the desert was 28.8 mg kg−1, being comparable to the low fertilizer treatment but approximately double that of unfertilized cotton, suggesting N fixing capacity of the leguminosae A. sparsifolia. Available K content was highest in desert and decreased with cultivation intensity. There were positive relationships between SOC and available N and P contents, suggesting SOC as a nutrient reservoir. Soil C:N ratio during 2010–2013 increased with intensity, being 8.7, 9.7, 10.8, and 12.0, for desert, no fertilizer, low, and high fertilizer input, respectively. Fertilizer application increased the 2010–2013 average cotton seed yield by 4.3–6.4 times compared to the unfertilized cotton field. In conclusion, our results suggest the intensive inputs of fertilizers are crucial to accelerate soil fertility and maintain the productivity of the recently converted lands from the desert.

Effects of different fertilizer strategies on soil water utilization and maize yield in the ridge and furrow rainfall harvesting system in semiarid regions of China

Shortages of water resources and low soil fertility are two key factors that limit crop production in semiarid areas. The ridge and furrow rainfall harvesting (RFRH) system is an effective method for enhancing the efficiency of rainfall water use and fertility. In this study, we conducted a field experiment over five years (2012–2016) to determine the effects of different fertilizer application rates on the soil water consumption properties, water use efficiency, and maize yield under RFRH. We found that the evapotranspiration (ET), maize dry matter (DM), water consumption strength (CD), and soil water use rate (SP) increased with the fertilizer application rate. Compared with the no fertilizer treatment (RCK), ET, DM, CD, and SP increased significantly by 7.2%, 38.3%, 16.4%, and 37.6% under high fertilizer (RH) treatment, respectively, by 6.7%, 35.8%, 18.0%, and 39.1% with medium fertilizer (RM) treatment, and by 5.5%, 31.1%, 16.1%, and 32.6% with low fertilizer (RL) treatment. RM achieved the highest average yield of 11.3 t ha–1 and the lowest coefficient of variation at 12.9%. The yield, DM, and water use efficiency did not differ significantly between RH and RM. Regression analysis showed that the highest yield could be obtained by applying nitrogen at 265.0 kg ha–1 combined with P2O5 at 132.5 kg ha–1. The yield and water use efficiency were significantly higher under RL compared with RH and RM in wet year. However, in both normal and drought years, the grain yield and water use efficiency was significantly higher under RM. These results indicate that the RFRH system can promote crop use of fertilizers by regulating soil moisture. The best fertilization strategy for planting maize with RFRH system was 265.0 kg ha–1 of pure nitrogen combined with 132.5 kg ha–1 of P2O5 in the semiarid area of the Loess Plateau, in China.

Canola Nutrition and Variety Affect Oviposition and Offspring Performance in the Generalist Herbivore, Mamestra configurata (Lepidoptera: Noctuidae).

Bertha armyworm Mamestra configurata Walker (Lepidoptera: Noctuidae) is a generalist herbivore that feeds on several crops in different plant families. Canola Brassica napus L. (Capparales: Brassicaceae) is one of the most favored host plants making the bertha armyworm a significant insect pest in the Canadian Prairie Provinces. The performance of the bertha armyworm on canola may vary with the quality of the canola plant. We tested the impact of plant nutrition and canola variety on oviposition and subsequent larval development of the bertha armyworm. A range of fertilization levels (0.0, 1.0, 3.0, and 5.0 g/pot) were applied to three different canola varieties: Clearfield 5535 CL, Roundup Ready hybrid 6060RR, and Q2. The total number of eggs laid on plants in a no-choice experiment increased with fertilizer level but a similar number of eggs were laid on plants that received moderate and high fertilizer treatments. Larvae reared on plants that received the moderate fertilizer application yielded heavier pupae than those reared on plants with low and high fertilizer treatments. Most eggs were laid on the Q2 variety when compared to Clearfield 5535 CL and Roundup Ready 6060 RR. Bertha armyworm females preferred to lay eggs on plants that received moderate or high fertilization over plants with the low fertilizer treatment. Plant leaf tissue nutrient content and plant growth were highest in plants that received moderate and high fertilizer treatment. We conclude that bertha armyworm oviposition behavior and larval performance are influenced by fertilizer treatment and canola variety.

Endometrial injury for pregnancy following sexual intercourse or intrauterine insemination.

Endometrial injury for pregnancy following sexual intercourse or intrauterine insemination.

Quinoa Seed Quality Response to Sodium Chloride and Sodium Sulfate Salinity.

Quinoa (Chenopodium quinoa Willd.) is an Andean crop with an edible seed that both contains high protein content and provides high quality protein with a balanced amino acid profile in embryonic tissues. Quinoa is a halophyte adapted to harsh environments with highly saline soil. In this study, four quinoa varieties were grown under six salinity treatments and two levels of fertilization, and then evaluated for quinoa seed quality characteristics, including protein content, seed hardness, and seed density. Concentrations of 8, 16, and 32 dS m-1 of NaCl and Na2SO4, were applied to the soil medium across low (1 g N, 0.29 g P, 0.29 g K per pot) and high (3 g N, 0.85 g P, 0.86 g K per pot) fertilizer treatments. Seed protein content differed across soil salinity treatments, varieties, and fertilization levels. Protein content of quinoa grown under salinized soil ranged from 13.0 to 16.7%, comparable to that from non-saline conditions. NaCl and Na2SO4 exhibited different impacts on protein content. Whereas the different concentrations of NaCl did not show differential effects on protein content, the seed from 32 dS m-1 Na2SO4 contained the highest protein content. Seed hardness differed among varieties, and was moderately influenced by salinity level (P = 0.09). Seed density was affected significantly by variety and Na2SO4 concentration, but was unaffected by NaCl concentration. The samples from 8 dS m-1 Na2SO4 soil had lower density (0.66 g/cm3) than those from 16 dS m-1 and 32 dS m-1 Na2SO4, 0.74 and 0.72g/cm3, respectively. This paper identifies changes in critical seed quality traits of quinoa as influenced by soil salinity and fertility, and offers insights into variety response and choice across different abiotic stresses in the field environment.

Phylogenetic structure of arbuscular mycorrhizal community shifts in response to increasing soil fertility

Understanding the underlying mechanisms driving responses of belowground communities to increasing soil fertility will facilitate predictions of ecosystem responses to anthropogenic eutrophication of terrestrial systems. We studied the impact of fertilization of an alpine meadow on arbuscular mycorrhizal (AM) fungi, a group of root-associated microorganisms that are important in maintaining sustainable ecosystems. Species and phylogenetic composition of AM fungal communities in soils were compared across a soil fertility gradient generated by 8 years of combined nitrogen and phosphorus fertilization. Phylogenetic patterns were used to infer the ecological processes structuring the fungal communities. We identified 37 AM fungal virtual taxa, mostly in the genus Glomus. High fertilizer treatments caused a dramatic loss of Glomus species, but a significant increase in genus richness and a shift towards dominance of the lineage of Diversispora. AM fungal communities were phylogenetically clustered in unfertilized soil, random in the low fertilizer treatment and over-dispersed in the high fertilizer treatments, suggesting that the primary ecological process structuring communities shifted from environmental filtering (selection by host plants and fungal niches) to a stochastic process and finally to competitive exclusion across the fertilization gradient. Our findings elucidate the community shifts associated with increased soil fertility, and suggest that high fertilizer inputs may change the dominant ecological processes responsible for the assembly of AM fungal communities towards increased competition as photosynthate from host plants becomes an increasingly limited resource.

A negative heterogeneity–diversity relationship found in experimental grassland communities

Recent meta-analyses and simulation studies have suggested that the relationship between soil resource heterogeneity and plant diversity (heterogeneity-diversity relationship; HDR) may be negative when heterogeneity occurs at small spatial scales. To explore different mechanisms that can explain a negative HDR, we conducted a mesocosm experiment combining a gradient of soil nutrient availability (low, medium, high) and scale of heterogeneity (homogeneous, large-scale heterogeneous, small-scale heterogeneous). The two heterogeneous treatments were created using chessboard combinations of low and high fertility patches, and had the same overall fertility as the homogeneous medium treatment. Soil patches were designed to be relatively larger (156 cm(2)) and smaller (39 cm(2)) than plant root extent. We found plant diversity was significantly lower in the small-scale heterogeneous treatment compared to the homogeneous treatment of the same fertility. Additionally, low fertility patches in the small-scale heterogeneous treatment had lower diversity than patches of the same size in the low fertility treatment. Shoot and root biomass were larger in the small-scale heterogeneous treatment than in the homogeneous treatment of the same fertility. Further, we found that soil resource heterogeneity may reduce diversity indirectly by increasing shoot biomass, thereby enhancing asymmetric competition for light resources. When soil resource heterogeneity occurs at small spatial scales it can lower plant diversity by increasing asymmetric competition belowground, since plants with large root systems can forage among patches and exploit soil resources. Additionally, small-scale soil heterogeneity may lower diversity indirectly, through increasing light competition, when nutrient uptake by competitive species increases shoot biomass production.

Effect of Different NPK Fertilizers Cooperating Application on Yield and Quality of High Starch Maize

Effect of nitrogen, phosphorus and cooperation application on grain yield and qualities of high starch maize Zhengdan 18 was studied. Six different fertilization treatments based on the random-plot experiment. The results indicated that N fertilizer significantly increased yield, as compared with the non-fertilizer treatment, the yield with the combined application of N and P fertilizers was higher than that of maize with single N treatment, the yield with the combined application of N P and K fertilizers was superior to that of maize with the combined application of N and P fertilizers. The yield was increased with the increase of the fertilization amount of the combined application of N, P and K, but there was not the direct proportion between yield and fertilization amount in the growth period, obeying the reward descending rule. The number of grains of ear was important for seed yield. The experiments showed the contents of starch, lipid and protein were increased along with the increase of N fertilization amount. The content of starch was increased in the early stage and reduced in the late stage of postulation, At the same time, The contents of lipid and starch were not increased along with the increase of phosphorus fertilizer, The same is that the contents of lipid with the combined application of N, P and k fertilizers were higher than that of the combined application of N and P fertilizers, the accumulation of lipid was increased, while the accumulation of starch and protein were not increased with the increase of K fertilizers. The contents of protein, starch and lipid were higher in the early stage than that in the late stage of postulation with the low-fertilizer treatment. The accumulation of starch was increased with the increase of the amount of the combined application of N, P and k fertilizers, the content of protein and lipid were increased in its early growth stage, while its content was not increased in the late growth period. Considering for the economic performance and the balanced principle for the supply and demand of applying fertilizer, currently the best applying fertilizer treatment is: N: 225kg/hm2, P2O5 :112.5kg/hm2.

Greenhouse tomato–cucumber yield and soil N leaching as affected by reducing N rate and adding manure: a case study in the Yellow River Irrigation Region China

The effect of reducing N rate fertilization and manure addition on greenhouse vegetable yields and soil N leaching was studied in a greenhouse tomato–cucumber rotation system in the Yellow River Irrigation Region of Ningxia Plain, North China. The treatments were: 1-no fertilizers, 2-conventional fertilization, 3-reduced fertilizer application, and 4-reduced fertilizer application + regulation of soil C/N ratio applied by the high C/N ratio of dairy manure. The results indicated that reduced fertilizer application in tomato and cucumber season had no significant influence on vegetable yield comparing with control. The amounts of leachate had no significant differences under all fertilizer treatments at the same investigated period. In comparison with conventional fertilization, both total N and NO3–N leaching decreased in the low fertilizer treatments. The cumulative total N and NO3–N leached from fertilizers N were less than 9 % during the tomato–cucumber rotation system. NO3–N was the predominant form of leaching N, represented about 70 % of total N in the leachate. Soluble organic N represented 14.7–33.3 % of total N leached. Vegetable yields did not increase significantly as applied N rates increased. However, soil N leaching increased largely with N rates. Reducing fertilizer N rate while adding dairy manure regulated soil C/N ratio could be appropriate fertilization practices for reducing soil N leaching and achieving high vegetable yields in the greenhouse systems.

The influences of mineral fertilization and crop sequence on sustainability of corn production in northeastern China

A sustainable agricultural production can be divided into three aspects, namely high crop productivity, stable yield and improved soil quality. The long-term effects of mineral fertilizers and crop sequence on corn (Zea mays L.) productivity, yield stability and soil fertility properties were studied on an Alfisol in northeastern China, based on a consecutive 18-year field trial. The results showed that the balanced mineral fertilization and preceding soybean could increase and stabilize the corn yield, and the influence of fertilization on yield performance was more obvious than crop sequence. In all treatments, soil organic carbon (SOC) and total N (TN), which were the key soil properties to improve corn yield and stability, declined from the initial level. Application of N tended to cause soil acidification, but no significant reduction in corn yield has been observed due to pH decrease over the study period. The decrease in SOC, TN and soil pH, however, were probably potential threats to sustainable development of agriculture. Furthermore, the relationship between yield and relative aridity index was statistically significant (P<0.01), and the optimum range of aridity index for high and stable yield was from 0.89 to 1.11 in this region. Water supply in April plays a critical role in achieving high and stable yield, especially for the low fertility treatments. Overall, our results provided insights for nutrients and water management in sustainable agriculture.

Effect of Saturated Near Surface on Nitrate and Ammonia Nitrogen Losses in Surface Runoff at the Loess Soil Hillslope

Water pollution from agricultural fields is a global problem and cause of eutrophication of surface waters. A laboratory study was designed to evaluate the effects of near-surface hydraulic gradients on NO3–N and NH4–N losses in surface runoff from soil boxes at 27% slope undersimulated rainfall of a loess soil hillslope. Experimental treatments included two near-surface hydraulic gradients (free drainage, FD; saturation, SA), three fertilizer application rates (control, no fertilizer input; low, 120 kg N ha-1; high, 240 kg N ha-1), and simulated rainfall of 100 mm h-1was applied for 70 min. The results showed that saturated near-surface soil moisture had dramatic effects on NO3–N and NH4–N losses and water quality. Under the low fertilizer treatment, average NO3–N concentrations in runoff water of SA averaged 2.2 times greater than that of FD, 1.6 times greater for NH4–N. Under the high fertilizer treatment, NO3–N concentrations in runoff water from SA averaged 5.7 times greater than that of FD, 4.3 times greater for NH4–N. Nitrogen loss formed with NO3–N is dominant during the event, but not NH4–N. Under the SA condition, the total loss of NO3–N from low fertilizer treatment was 34.2 to 42.3% of applied nitrogen, while under the FD treatment that was 3.9 to 6.9%. However, the total loss of NH4–N was less than 1% of applied nitrogen. These results showed that saturated condition could make significant contribution to water quality problems.