Maize yield response to water supply and fertilizer input in a semi-arid environment of Northeast China.

Maize grain yield varies highly with water availability as well as with fertilization and relevant agricultural management practices. With a 311-A optimized saturation design, field experiments were conducted between 2006 and 2009 to examine the yield response of spring maize (Zhengdan 958, Zea mays L) to irrigation (I), nitrogen fertilization (total nitrogen, urea-46% nitrogen,) and phosphorus fertilization (P2O5, calcium superphosphate-13% P2O5) in a semi-arid area environment of Northeast China. According to our estimated yield function, the results showed that N is the dominant factor in determining maize grain yield followed by I, while P plays a relatively minor role. The strength of interaction effects among I, N and P on maize grain yield follows the sequence N+I >P+I>N+P. Individually, the interaction effects of N+I and N+P on maize grain yield are positive, whereas that of P+I is negative. To achieve maximum grain yield (10506.0 kg · ha(-1)) for spring maize in the study area, the optimum application rates of I, N and P are 930.4 m(3) · ha(-1), 304.9 kg · ha(-1) and 133.2 kg · ha(-1) respectively that leads to a possible economic profit (EP) of 10548.4 CNY · ha(-1) (CNY, Chinese Yuan). Alternately, to obtain the best EP (10827.3 CNY · ha(-1)), the optimum application rates of I, N and P are 682.4 m(3) · ha(-1), 241.0 kg · ha(-1) and 111.7 kg · ha(-1) respectively that produces a potential grain yield of 10289.5 kg · ha(-1).

Quantifying spatial variability of selected soil trace elements and their scaling relationships using multifractal techniques.

Multifractal techniques were utilized to quantify the spatial variability of selected soil trace elements and their scaling relationships in a 10.24-ha agricultural field in northeast China. 1024 soil samples were collected from the field and available Fe, Mn, Cu and Zn were measured in each sample. Descriptive results showed that Mn deficiencies were widespread throughout the field while Fe and Zn deficiencies tended to occur in patches. By estimating single multifractal spectra, we found that available Fe, Cu and Zn in the study soils exhibited high spatial variability and the existence of anomalies ([α(q)max-α(q)min]≥0.54), whereas available Mn had a relatively uniform distribution ([α(q)max-α(q)min]≈0.10). The joint multifractal spectra revealed that the strong positive relationships (r≥0.86, P<0.001) among available Fe, Cu and Zn were all valid across a wider range of scales and over the full range of data values, whereas available Mn was weakly related to available Fe and Zn (r≥0.18, P<0.01) but not related to available Cu (r = -0.03, P = 0.40). These results show that the variability and singularities of selected soil trace elements as well as their scaling relationships can be characterized by single and joint multifractal parameters. The findings presented in this study could be extended to predict selected soil trace elements at larger regional scales with the aid of geographic information systems.

[Fractal theory and its application in the analysis of soil spatial variability: a review].

Soil has spatial variability in its attributes. The analysis of soil spatial variability is of significance for soil management. This paper summarized the fractal theory and its application in spatial analysis of soil variability, with the focus on the utilization of moment method in calculating the fractal dimension of soil attributes, the multi-fractal analysis of soil spatial variability, and the scaling up of soil attributes based on multi-fractal parameters. The studies on the application of fractal theory and multi-fractal method in the analysis of soil spatial variability were also reviewed. Fractal theory could be an important tool in quantifying the spatial variability and scaling up of soil attributes.

[Fractal characteristics of visible spectra across a hilly area].

The spectral characteristic of remotely sensed image is mainly the results of integrative effects on spectrum from heterogeneous ground reflectors. Investigating its spatial distribution characteristics may be helpful for image interpreting and modeling based on remote sensing technique. In the present study, spatial heterogeneity of remotely sensed multispectral TM image across a hilly area in late October was studied by the combination of statistical method and multifractal analysis. The results showed that distribution of digital number (DN) values of visible spectra (0.45-0.69 microm) had statistical scale-invariance. The generalized fractal dimension function D(q) suggested that distribution of TM 2 (0.52-0.60 microm) DN values was monofractal type, whereas DN values of TM 1 (0.45-0.52 microm) and TM 3 (0.63-0.69 microm) had multifractal distribution characteristics. The parameters (alpha(max)-alpha(min)) and [f(a(max))-f(alpha(min))] of multifractal spectra further indicated that TM 3 DN values had the high est spatial heterogeneity and most abundant information, followed by TM 1, while the extremely narrow spectrum of TM 2 DN values showed its relatively low spatial heterogeneity and information capacity.

Characterizing scale- and location-dependent correlation of water retention parameters with soil physical properties using wavelet techniques.

Understanding the correlation between soil hydraulic parameters and soil physical properties is a prerequisite for the prediction of soil hydraulic properties from soil physical properties. The objective of this study was to examine the scale- and location-dependent correlation between two water retention parameters (alpha and n) in the van Genuchten (1980) function and soil physical properties (sand content, bulk density [Bd], and organic carbon content) using wavelet techniques. Soil samples were collected from a transect from Fuxin, China. Soil water retention curves were measured, and the van Genuchten parameters were obtained through curve fitting. Wavelet coherency analysis was used to elucidate the location- and scale-dependent relationships between these parameters and soil physical properties. Results showed that the wavelet coherence between alpha and sand content was significantly different from red noise at small scales (8-20 m) and from a distance of 30 to 470 m. Their wavelet phase spectrum was predominantly out of phase, indicating negative correlation between these two variables. The strong negative correlation between alpha and Bd existed mainly at medium scales (30-80 m). However, parameter n had a strong positive correlation only with Bd at scales between 20 and 80 m. Neither of the two retention parameters had significant wavelet coherency with organic carbon content. These results suggested that location-dependent scale analyses are necessary to improve the performance for soil water retention characteristic predictions.

Identification of Aspergillus section Flavi in maize in northeastern China.

Species of Aspergillus section Flavi were isolated and identified in maize samples collected from a wide geographical region in northeastern China. Aspergillus flavus was identified to be the primary species in the population (99%) becoming a potential source of aflatoxin contamination in the region. Isolated A. flavus strains were classified into the S and L strains respectively based on their sclerotia morphology. Among the A. flavus strains identified, L strains dominated over the S strains in the maize samples studied. Both uniseriate and biseriate forms were observed in A. flavus L strain isolates. However, only uniseriate was observed in A. flavus S strain isolates. Microscopic characteristics of L and S strains were observed and reported. Some geographical differences between northeastern China and other countries and regions were discussed. This is the first study on the population dynamics of A. flavus versus A. parasiticus and the L and S strains within A. flavus in maize samples in northeastern China.

[Plantation stocks and their affecting factors in western Liaoning Province].

Employing real-site investigation and data analysis methods, this paper analyzed the distribution of plantation stocks and its affecting factors in western Liaoning Province. The results showed that the average plantation stock of western Liaoning was 49.08 m3.hm(-2), which has been improved obviously since 1949. At the time of the third forest resource investigation, the plantation stock increased 20.19 m3.hm(-2), 5.16 times higher than that of the first forest resource investigation. But, the general plantation stock of western Liaoning was still at a rather lower level, with only a 63.5% increase of the whole province and 51.1% of the national average plantation stock at the same period. The difference of plantation stock among cities in western Liaoning was observable, that even reached 68.47 m3.hm(-2). In general, the proportion of young forest was too high, reached to 49 % of the total plantation, while the stock of mature forest was much lower, only 38% of the national average level. The plantation stock of national property was only 55.1% and 32.3% of the personal and collective property, respectively. Moreover, the plantation stock of timber forest was 36.4% lower than that of windbreak. Besides climatic factors, simple plantation structure, few forest tree species, and poor plantation management were the main causes of the low plantation stock.

[Climatic productivity of plantations in western Liaoning area].

Calculations by six models of climatic productivity showed that the average climatic productivity of plantations in western Liaoning area was 8.8 t x hm(-2) x yr(-1), and had a decreasing trend from southeast to northwest, which was coincided with the distribution of rainfall. Three models were suitable to be used to calculate the climatic productivity of plantations in the area. The present plantation productivity was really lower than the potential climatic productivity, and the great potential was available in improving plantation productivity through the improvement of forest quality.

[On water saving agriculture and water resource sustainable utilization in Northeastern China].

A strategy of systematic water saving agriculture was proposed based on the analysis of the water resource shortage regime and the agricultural water saving potential under the background of promoting the old industrial bases in Northeastern China. Different pattern areas of water saving agriculture were divided, and integrated water saving technique systems and water saving cultivation models were recommended, according to their agricultural production characteristics and development requirement in the future. The systematic strategy for sustainable utilization of water resource, the necessity of applying project for water saving and regulating rivers and watercourses synthetically, and the trends in water saving research in Northeastern China were discussed.

[An overview on theoretic research of high efficient water use in agriculture].

High efficient water use in agriculture includes water-saving irrigation and dryland farming, its core being to increase use efficiency and benefit of natural precipitation and irrigation. Each of measurement methods of field evapotranspiration has its advantages and disadvantages. Modified Penman and Penman-Monteith formulae were recommended to calculate the reference crop evapotranspiration by FAO one after another. Jensen and Blank models had a wide use in crop water production function. Recent achievements of appropriate soil moisture and lower limit of soil drought indices provided an important basis of soil physics for agricultural water supply of low quota. The influencing sequence of water stress on different physiological processes correlated with yield formation was in order of cell stretch > stoma movement > transpiration > photosynthesis > matter transfer. Non-severe drought could facilitate matter transfer. Field irrigation research has turn to deficit irrigation, regulated deficit irrigation and controlled alternative irrigation from traditional full irrigation. In the future, such researches as interfaces, soil water dynamics, biological water-saving and water stress would be deeply conducted in high efficient water use theory in agriculture.

[Soil quality and its evaluation].

Preservation and improvement of soil quality is the basic task for agricultural sustainable development. For this reason, the concept and the evaluation method of soil quality should be clearly understood. In this paper, the concept of soil quality and its advanced researches were reviewed. Soil quality evaluation should be based on soil function, different types of soils should be evaluated by different criterions, and soil quality evaluation should be relational rather than absolute as well. Some methods of soil quality evaluation were introduced, and the selection of evaluation indicators was discussed.

[Seeping irrigation effect in sunlight greenhouse].

The differences of soil and air environments, crop growth, development and diseases, and water use efficiency of seeping irrigation from furrow irrigation were studied. Results indicated that compared with furrow irrigation, seeping irrigation could increase soil waterstable granular by 81.4%, soil porosity by 29.0% and soil temperature by 1.1-1.7 degrees C respectively, decrease bulk density by 21.2% and relative air humidity by 13.4% respectively, and save irrigation water by 36.7%. In addition, seeping irrigation could also accelerate crop maturity and increase yield, reduce crop diseases and production cost. Therefore, seeping irrigation was an ideal irrigation technique in sunlight greenhouse at present.