Long-term fertilization effects on grain yield, water-use efficiency and soil fertility in the dryland of Loess Plateau in China

https://doi.org/10.1016/j.agee.2004.09.003Get rights and content

Abstract

Wheat (Triticum aestivum L.) and corn (Zea mays L.) rotation system is important for food security in the Loess Plateau of China. Grain yield and water-use efficiency (WUE: grain yield per unit of water consumed) trends, and changes in soil properties during a 24-year fertilization experiment in Pingliang, Gansu, China, were recorded. Mean yields of wheat for the 16 years started in 1981 ranged from 1.29 t ha−1 for the unfertilized plots (CK) to 4.71 t ha−1 for the plots that received manure (M) annually with inorganic nitrogen (N) and phosphorus (P) fertilizers (MNP). Corn yields for the 6 years started in 1979 averaged 2.29 and 5.61 t ha−1 in the same treatments. Yields and WUEs declined significantly with lapse of time except CK and MNP for wheat. Wheat yields with the N and M declined at rate of 77 and 81 kg ha−1 year−1, but the decline of 57 kg ha−1 year−1 for NP was similar to that of 61 ha−1 year−1 for straw with N annually and P every second year (SNP). Likewise, the corn yields and WUEs declined from 160 to 250 kg ha−1 year−1 and from 0.01 to 0.03 kg m−3 year−1 among treatments, respectively. These declines were likely to loss of soil fertility and gradual dry weather. Yields were significantly correlated with seasonal evapotranspiration with slopes ranging from 0.5 to 1.27 kg m−3 for wheat and from 1.15 to 2.03 kg m−3 for corn. Soil organic carbon (SOC), total N (TN), and total P (TP) gradually built up with time except the CK, in which TN and TP remained unchanged but SOC and available P (AP) decreased. Soil AP decreased in the N. Soil available K declined rapidly without straw or manure. Balanced fertilization should be encouraged to ensure sustainable productivity in this intensive cropping system. The greatest SOC increases of about 160 mg ha−1 year−1 occurred in the SNP and MNP, suggesting that long-term additions of organic materials to soil could increase soil water-holding capacity which, in return, improves water availability to plants and arrests yield declines, and decrease CO2 emission from agricultural soils and sustain land productivity.

Introduction

Northwest China is a vast semi-arid area with average annual precipitation ranging from 300 to 600 mm and more than 90% of the cropland in this area receives no irrigation. The main crops are wheat (Triticum aestivum L.) and corn (Zea mays L.) which are periodically rotated. This rotation is a necessary for food security in this dryland region (Xing et al., 2001). In this system, three or more years of continuous wheat are commonly grown and then rotated to two or more years of continuous corn. Winter wheat is seeded about 20 September and harvested in late June. Corn is seeded about 20 April and harvested near the end of September. In a typical system where winter wheat follows corn, there is no fallow and wheat is seeded immediately following corn harvest. In all other combinations, land is fallowed between crops, which is helpful for water storage to store water in the soil for the subsequent crop. Shangguan et al. (2002) reported that fallow efficiencies, expressed as soil water accumulation divided by precipitation received during fallow periods, for the area were about 35–40%. The importance of storing soil water during fallow periods for increasing grain yields of subsequent crops has been supported by many dryland studies including those in the Southern Great Plains in USA by Johnson (1964), Unger (1972), Musick et al. (1994) and in the China Loess Plateau by Shangguan et al. (2002).

There are about 1.3 million ha of wheat and corn rotations in the Loess Plateau region of Northwest China. These lands are mostly in the highland plateaus of East Gansu and North Shaanxi and West Shanxi and account for about 40% of the local food needs (Fan and Song, 2000). The highland plateau is a relatively continuous integrated grain production belt among the hills and gullies of the Loess Plateau, and has an annual precipitation of 500–600 mm. The productivity of grain crops is affected significantly by water availability and fertilization. The importance of fertilization for increasing yield and improving soil quality in this area has been affirmed. Lu et al. (1998) reported that inorganic nitrogen (N) and phosphorus (P) fertilization increased grain yields in China by 50–60%. They stated that grain production in the region was not keeping pace with demand even though the area population growth rate was less than 1%. This is because highly erodible land is being retired to grassland and acreage for higher income crops is expanding. Improving the sustainable productivity of the cropland and increasing water-use efficiency by optimizing the relationships between nutrients and water will be required to meet the food demand of the region's growing population. Maintenance of soil fertility will be essential to improve and sustain yields, and soil organic matter (SOM) management is necessary as it directly and indirectly affects various chemical, physical, and biological soil properties that affect crop performance. SOM is recognized as a cornerstone for successful farming in most areas (Vanlauwe et al., 2001, Merckx et al., 2001, Zhang and He, 2004). Challenges for dryland farming in Northwest China are low water-use efficiency (WUE), expressed as grain yield per unit of water consumed, resulting from low SOM and low soil fertility (Zhu, 1984, Zhang et al., 1997). In most cases, organic carbon in the surface layer of this region was generally below 5.8 g kg−1 (Xing et al., 2001) because low-quality manure are applied at rate of 30 t ha−1 and crop straws are taken out from field for feed or fuel.

Long-term fertilization experiments are valuable to follow yield and soil fertility trends with lapse of time, changes in yields and WUE, and risk management (Dawe et al., 2000, Regmi et al., 2002). Various long-term experiments were done to test effects of fertilization on yield and soil properties in the world (Jenkinson, 1991, Mitchell et al., 1991, Sandor and Eash, 1991, Brown, 1991, Bhandari et al., 1992). Although there have been many field trials on fertilizer yield responses in northwest China, however, most of these studies have been carried out within a short period of time and can provide only preliminary fertilizer recommendations, which need further calibration through multi-year field experiments. Long-term changes in soil fertility and yield are therefore not well documented in this region. The study reported here was began in 1979 at Pingliang, Gansu, China, and is the oldest running and exclusive experiment of annual cropping systems in the Loess Plateau. The study aimed to (1) examine yield and WUE trends for wheat and corn in annual cropping systems under long-term organic and inorganic fertilization and (2) monitor long-term effects of fertilization on soil properties.

Section snippets

Experimental site

A long-term permanent plot experiment has been conducted since April 1979 at the Gaoping Agronomy Farm, Pingliang, Gansu, China. The site is in the central part of the Shizi highland plateau (35°16′N, 107°30′E, 1254 m altitude) in Pingliang. Its dark loessial soils are Calcarid Regosols (FAO/UNESCO, 1988) with an average SOM of 9.1 g kg−1, corresponding to about 5.3 g kg−1 of soil organic carbon (SOC). Soil texture of the 0–20 cm depth is silty loam (sand 231 g kg−1, silt 432 g kg−1, and clay 336 g kg−1)

Crop water stress index

There were large differences in the amounts and distribution patterns of GSP, fallow period intervals, and PET and CWSI values for the various annual cropping systems (Table 1). For the 16 years of wheat, the average GSP, estimated seasonal ET, PET, and CWSI values were 289 mm, 384 mm, 929 mm, and 0.57, respectively. The coefficients of variance (CV) for ET, PET, and CWSI were 24.9, 24.5, 12.0, and 24.6% in the same respective order. The CWSI was highly negatively correlated with ET (r = −0.98) and

Discussion

The search for reasons to explain the yield decline in this dryland field experiment was difficult because soil properties were changing both negatively and positively depending on the fertilization treatment, but the gradual dry weather should be a major reason because grain yields are highly correlated with ET and CWSI as discussed earlier. Nonetheless, the yield declines observed may also be considered as an indication for a reduction in soil fertility and unbalanced nutrient supply

Conclusions

The objectives of this study were to follow yield and WUE trends for wheat and corn in annual cropping systems under a 24-year dryland fertilization experiment, and monitor long-term effects of fertilization on soil properties. Results showed that the addition of organic materials and inorganic fertilizers significantly enhanced grain yields, water use, and soil properties if compared to no additives or addition of only inorganic nitrogen and phosphorus. Overall, the yields and WUEs for both

Acknowledgements

This study was financially supported by Chinese Ministry of Science and Technology under Key Technologies R&D Programme 2001BA508B11, a special support for China Scholarship Council. These assistances are gratefully acknowledged. We also thank staffs of Pingliang Agriculture Institute for their long-term field crop management in various phases of this study, and appreciate our teamwork colleagues who provide us with unpublished data.

References (46)

  • R.H. Bray et al.

    Determination of total, organic and available forms of phosphorus in soils

    Soil Sci.

    (1945)
  • J.R. Brown

    Summary: long-term field experiments symposium

    Agron. J.

    (1991)
  • T.L. Fan et al.

    Grain production and yield-increasing technologies of Loess Highland in North China

  • Soil Map of the World: Revised Legend

    (1988)
  • Crop Evapotranspiration: Guideline for Computing Crop Water Requirements

    (1998)
  • D.M. Freebairn et al.

    HOWWET?—A tool for predicting fallow water storage

  • R.D. Jackson et al.

    A reexamination of the crop water stress index

    Irrig. Sci.

    (1988)
  • D.S. Jenkinson

    The Rothamsted long-term experiments: are they still of use?

    Agron. J.

    (1991)
  • W.C. Johnson

    Some observations on the contribution of an inch of seeding-time soil moisture to wheat yields in the Great Plains

    Agron. J.

    (1964)
  • A. Krauss

    Soil potassium mining in the WANA region, a matter of concern?

  • R. Lal

    Land use and cropping systems effects on restoring soil carbon pools of degraded Alfisols in Western Nigeria

  • R.L. Liu et al.

    Study on the characteristics of potassium cycling in different soil–crop systems in northern China (in Chinese with English abstract)

    Plant Nutr. Fertil. Sci.

    (2000)
  • S.T. Liu et al.

    Effects of long-term fertilization on dynamics of phosphorus and potassium in soil (in Chinese with English abstract)

    Ecol. Environ.

    (2003)
  • Cited by (207)

    View all citing articles on Scopus
    View full text