Mingde Hao

Phosphorus Changes and Sorption Characteristics in a Calcareous Soil Under Long-Term Fertilization

Knowledge of phosphorus (P) behavior in long-term fertilized soils is essential for programming fertilization practices and for sustaining environmental quality. The long-term (1984-1997) effects of various fertilization treatments on P changes and sorption isotherms as well as the relationship of soil properties to P sorption and P forms were evaluated in an Ustic Isohumisol, a calcareous soil, on the Loess Plateau, China. Compared to 1984, after 13 years of crop production, total soil P in the no-P treatments (control and N treatment) decreased by 5%-7%, but in the phosphorus fertilizer alone (P), nitrogen and phosphorus fertilizers in combination (NP), manure alone (M), and nitrogen and phosphorus fertilizers and manure in combination (NPM) treatments, it increased by 22%, 19%, 28%, and 58%, respectively. Residual fertilizer P was found mainly in NH(4)Ac-soluble P (Ca(8)-P), followed by NaHCO(3)-soluble P (NaHCO(3)-P), and NH(4)F-soluble P (AI-P). Phosphorus sorption in the soils with different fertilization practices fit the Langmuir equations. Phosphorus sorption capacity in the no-P treatments increased, whereas it decreased in the P-included treatments (P, NP, and NPM treatments). Phosphorus sorption maximum (Q.) was significantly and negatively correlated to inorganic P including NaHCO(3)-P, Ca(8)-P, NaOH-Na(2)CO(3)-soluble P (Fe-P), and Al-P (P <= 0.01). Moreover, long-term fertilization increased soil organic carbon in the NP, M, and NPM treatments and decreased pH in the NP and NPM treatments. Thus, the ability of the soil to release sorbed P to the environment increased under long-term P fertilization.

Wheat Grain Yield and Yield Stability in a Long-Term Fertilization Experiment on the Loess Plateau

To provide a scientific basis for sustainable land management, a 20-year fertility experiment was conducted in Changwu County, Shaanxi Province, China to investigate the effects of long-term application of chemical fertilizers on wheat grain yield and yield stability on the Loess Plateau using regression and stability analysis. The experiment consisted of 17 fertilizer treatments, containing the combinations of different N and P levels, with three replications arranged in a randomized complete block design. Nitrogen fertilizer was applied as urea, and P was applied as calcium superphosphate. Fertilizer rates had a large effect on the response of wheat yield to fertilization. Phosphorus, combined with N, increased yield significantly (P < 0.01). In the unfertilized control and the N or P sole application treatments, wheat yield had a declining trend although it was not statistically significant. Stability analysis combined with the trend analysis indicated that integrated use of fertilizer N and P was better than their sole application in increasing and sustaining the productivity of rainfed winter wheat.

Nitrate leaching on loess soils in north-west China: Appropriate fertilizer rates for winter wheat

Abstract Nitrate leaching is an important factor affecting N fertilizer consumption in the agroecosystem of the Loess Plateau of China. Therefore, the movement and residual amounts of nitrate within the soil profile under different fertilizer application rates were studied to determine the most appropriate rates of fertilizer application. Soil samples were collected from a long-term experimental site to determine the concentration of nitrate in mid-September 1999 and 2007. The results showed that -N had moved more than 100 cm down the soil profile from 1999 to 2007, and two peaks of -N were present at different depths after 23 years of high rates of N application. -N had leached to depths exceeding 300 cm in plots where > 90 kg ha−1 N had been applied alone. At the fertilization rate of 180 kg N ha−1, up to 1500 kg ha−1 residual -N was detected, equivalent to 34.8% of the total input of N fertilizer during the experiment. The total amount of residual nitrate increased with increases in the N application rate, but decreased with increases in P2O5 application when the N application was up to 90 kg ha−1 or more. The results indicate that fertilization using a 1:1 mixture of N:P2O5 at 90 kg ha−1 p.a. could prevent -N from leaching in soil used to grow continuous winter wheat (Triticum aestivum L.) crops in the rain-fed agricultural areas of China, while providing optimum yields.

Dynamics and Availability of Different Pools of Manganese in Semiarid Soils as Affected by Cropping System and Fertilization

Abstract Manganese (Mn) deficiencies are common in soils on the Loess Plateau of China. This research provided essential information on improving Mn availability in semiarid soils through agricultural practices. Twelve cropping system and fertilization treatments were designed in a 28-year experiment. The cropping systems included long-term fallow, continuous winter wheat cropping, pea (1 year)-winter wheat (2 years)-millet (1 year) rotation (crop-legume rotation) cropping, and continuous alfalfa cropping. The fertilizer treatments under the cropping systems included no-fertilizer control (CK), application of P fertilizer (P), application of N and P fertilizers (NP), and application of N and P fertilizers and manure (NPM), but the NP treatment was excluded in the continuous alfalfa cropping system. Available Mn and Mn fractions of soil samples (0–20 and 20–40 cm depths) were measured and further analyzed quantitatively using path analyses. Results showed that the crop-legume rotation and continuous alfalfa cropping systems significantly increased available Mn compared with the fallow soil. Compared with the no-fertilizer control, manure application increased available Mn in soil of the continuous wheat cropping system. Across all treatments, the averaged content of mineral-, oxide-, carbonateand organic matter-bound and exchangeable Mn accounted for 42.08%, 38.59%, 10.05%, 4.59%, and 0.09% of the total Mn in soil, respectively. Cropping significantly increased exchangeable Mn in soil and the highest increase was 185.7% in the continuous wheat cropping system at 0–20 cm depth, compared with the fallow soil. Fertilization generally increased exchangeable and carbonate-bound Mn in soil. Carbonate-bound Mn was the main and direct source of available Mn in soil, followed by exchangeable and organic matter-bound Mn. These results indicated that crop-legume rotation cropping, continuous alfalfa cropping and application of manure, have the potential to promote Mn availability in soils of rainfed farmlands.

Changes in aggregate-associated organic carbon and nitrogen after 27 years of fertilization in a dryland alfalfa grassland on the Loess Plateau of China

Changes in the distribution of soil aggregate sizes and concentrations of aggregate-associated organic carbon (OC) and nitrogen (N) in response to the fertilization of grasslands are not well understood. Understanding these changes is essential to the sustainable development of artificial grasslands. For understanding these changes, we collected soil samples at 0–20 and 20–40 cm depths from a semi-arid artificial alfalfa grassland after 27 years of applications of phosphorus (P) and nitrogen+phosphorus+manure (NPM) fertilizers on the Loess Plateau of China. The distribution of aggregate sizes and the concentrations and stocks of OC and N in total soils were determined. The results showed that NPM treatment significantly increased the proportions of >2.0 mm and 2.0–0.25 mm size fractions, the mean geometric diameter (MGD) and the mean weight diameter (MWD) in the 0–20 cm layer. Phosphorous fertilizer significantly increased the proportion of >2.0 mm size fractions, the MGD and the MWD in the 0–20 cm layer. Long-term application of fertilization (P and NPM) resulted in the accumulation of OC and N in soil aggregates. The largest changes in aggregate-associated OC and N in the 0–20 cm layer were found at the NPM treatment, whereas the largest changes in the 20–40 cm layer were found at the P treatment. The results suggest that long-term fertilization in the grassland leads to the accumulation of OC and N in the coarse size fractions and the redistribution of OC and N from fine size fractions to coarse size fractions.

Effects of straw covering methods on runoff and soil erosion in summer maize field on the Loess Plateau of China

The objective of this paper is to clarify the impacts of straw covering method on runoff and soil erosion in summer maize field on the Loess Plateau of China. A field experiment was conducted (2012–2014) in the artificial rain ing hall of the State Key Laboratory, with three soils and five straw covering methods. Three soils were Heilu soil (Calcisols), Huangmian soil (Fluvisols) and Lou soil (Anthrosols). Five straw covering methods were CK – no straw mulching and no stubble standing on the surface of the plot; T30 – 30 cm of winter wheat (WW) stubble standing above ground; M30 – 30 cm of WW stubble was harvest and mulched on the surface of the plot; M10T20 – 20 cm of WW stubble standing and 10 cm WW straw mulching on the surface of the plot; M20T10 – 10 cm of WW stubble standing and 20 cm of WW straw mulching on the surface of the plot. The results showed that (1) straw cover ing method not only impacted ITRP (initial time of runoff producing), but also affected runoff volume in summer maize field on the Loess Plateau of China. M10T20 was the best to postpone ITRP and to reduce runoff volume in summer maize field. (2) Different covering methods produced different sediment yield in summer maize field. M30 was the best to reduce soil erosion in summer maize field on the Loess Plateau of China. (3) When one covering method was used to reduce runoff or soil erosion, bulk density and soil mechanical composition (silt content, clay content and sand content) should be considered seriously.

Contribution of fertilisation, precipitation, and variety to grain yield in winter wheat on the semiarid Loess Plateau of China

ABSTRACT Wheat yield is influenced by fertilisation, precipitation and variety, among other factors. There is limited research identifying the most important factors affecting wheat yield and assessing their relative importance in the long run. In this study, we evaluated the contribution of fertilisation, precipitation and variety to wheat yield using a long-term field experiment (1984–2014) on the semiarid Loess Plateau in China. The experiment consisted of six treatments: fertilisation with nitrogen (N), phosphorus (P), manure (M), NP, NPM, and a control without fertilisation. We monitored the yield of three varieties of winter wheat over time and assessed the changes in grain yield, soil properties, fertiliser-contribution rate (FCR) and precipitation-use efficiency (PUE) with different fertilisation treatments and precipitation patterns. Stepwise multiple linear regression was used to identify the most important factors affecting wheat yield and examine their relative importance. The results showed that fallow-season precipitation and annual precipitation (AnP) positively correlated with wheat yield in the N, M, NP, and NPM treatments. The amount of fertilisation, AnP, and monthly precipitation of February and September were included in the linear regression model; however, the influence of variety on yield could be ignored. With 30 years of fertilisation, soil organic matter, total nitrogen, and available potassium levels with NPM was higher than the control by 70.6%, 70.5%, and 319.2%, respectively. Yield, FCR, and PUE with M increased annually at rates of 89 kg ha−1 y−1, 1.47 kg kg−1 y−1, and 0.13 kg mm−1 y−1, respectively. The yields and FCR, but not PUE, of all fertilised treatments were higher in wet than normal and dry years. The FCR with P was negative in all the three precipitation patterns. This study has implications for maximising the long-term winter yield with various factors in the rain-fed winter wheat cropping system of the Loess Plateau.

Changes in Soil Iron Fractions and Its Availability after 28 Years in the Loess Belt of Northern China under Continuous Cultivation and Fertilization

Abstract Iron (Fe) deficiency in calcareous soils of the Loess Plateau of China is a wide spread issue and primarily affects agricultural production due to the relatively higher soil pH and carbonate content. Understanding the relationships between Fe distribution in soil fractions, Fe availability, and their responses to cropping and fertilization could provide essential information for assessing Fe availability in soils and managing soils to improve Fe availability. A long-term field experiment was established in 1984 in a split-plot design using cropping systems as main plots and fertilizer treatments as subplots on a farmland in the Loess Plateau. The cropping systems included fallow, continuous wheat cropping, continuous alfalfa cropping, continuous maize cropping, and a rotation system that included a legume. Various fertilization treatments using chemical and/or manure fertilizers were included in each cropping system. Soil samples were collected from 0–10 and 20–40 cm depths in 2012. Long-term planting of crops significantly increased the concentrations of available Fe in the soils. The largest increase was observed in the continuous alfalfa cropping system. Long-term cropping significantly increased the concentrations of Fe associated with carbonates and organic matter, but decreased the concentration of Fe associated with minerals in the soils. The effect of fertilization on the distribution of Fe in the soil fractions varied with cropping system and soil depth. The fertilization treatment with manure generally increased the concentrations of Fe associated with the soil fractions. Long-term cropping and fertilization in the highland farmland significantly affected the availability of Fe and the distribution of Fe fractions in the soil.

Long-Term Effect of Crop Rotation and Fertilisation on Bioavailability and Fractionation of Copper in Soil on the Loess Plateau in Northwest China

The bioavailability and fractionation of Cu reflect its deliverability in soil. Little research has investigated Cu supply to crops in soil under long-term rotation and fertilisation on the Loess Plateau. A field experiment was conducted in randomized complete block design to determine the bioavailability and distribution of Cu fractions in a Heilu soil (Calcaric Regosol) after 18 years of rotation and fertilisation. The experiment started in 1984, including five cropping systems (fallow control, alfalfa cropping, maize cropping, winter wheat cropping, and grain-legume rotation of pea/winter wheat/winter wheat + millet) and five fertiliser treatments (unfertilised control, N, P, N + P, and N + P + manure). Soil samples were collected in 2002 for chemical analysis. Available Cu was assessed by diethylene triamine pentaacetic acid (DTPA) extraction, and Cu was fractionated by sequential extraction. Results showed that DTPA-Cu was lower in cropping systems compared with fallow control. Application of fertilisers resulted in no remarkable changes in DTPA-Cu compared with unfertilised control. Correlation and path analyses revealed that soil pH and CaCO3 directly affected Cu bioavailability, whereas available P indirectly affected Cu bioavailability. The concentrations of Cu fractions (carbonate and Fe/Al oxides) in the plough layer were lower in cropping systems, while the values in the plough sole were higher under grain-legume rotation relative to fallow control. Manure with NP fertiliser increased Cu fractions bound to organic matter and minerals in the plough layer, and its effects in the plough sole varied with cropping systems. The direct sources (organic-matter-bound fraction and carbonate-bound fraction) of available Cu contributed much to Cu bioavailability. The mineral-bound fraction of Cu acted as an indicator of Cu supply potential in the soil.

Soil inorganic P fractions in a long-term fertility experiment on the Loess Plateau of China

Phosphorus (P) is an essential element for plant growth, so proper application of P fertilizers to farmland is necessary. High levels of P fertilization often cause P accumulation in soil and thereby increase P loss to the environment. The effect of long-term P fertilization on soil inorganic P (Pi) fractions and available P (Pa) stocks were investigated in order to provide a reference for rational management of P fertilization. A 27-year experiment was initiated in September 1984 in Changwu County on the southern part of the Loess Plateau, northern China. The experiment included five treatments of P fertilization: 0, 20, 40, 60, and 80 kg P ha−1. With zero P application, soil Pi fractions decreased and were even depleted over time. In fertilized plots, soil Pi content in available and unavailable fractions increased over time, regardless of the application rate. P fertilization increased the content and change rate of soil Pi fractions between three sampling times (1991, 2001, and 2011). Soil Pa stocks and plant P uptake increased with increasing application rate of 20–60 kg P ha−1, indicating increased input and output of P in the soil–plant system. Higher application rates (≥60 kg P ha−1) did not change soil Pa stocks or plant P uptake but increased the annual change rate of Pi fractions, maintaining a balance between the supply and demand of P. This study has implications for reducing P fertilization level and decreasing associated environmental risks in agricultural soil on the Loess Plateau.