Green Manuring in Crop Production

ABSTRACT

The positive role of green manuring in crop production has been known since ancient time. Importance of this soil ameliorating practice is increasing in recent years because of high cost of chemical fertilizers, increased risk of environmental pollution, and need of sustainable cropping systems. Green manuring can improve soil physical, chemical, and biological properties and consequently crop yields. Furthermore, potential benefits of green manuring are reduced nitrate (NO₃ ⁻) leaching risk and lower fertilizer N requirements for succeeding crops. However, its influence may vary from soil to soil, crop to crop, environmental variables, type of green manure crop used, and its management. Beneficial effects of green manuring in crop production should not be evaluated in isolation; however, in integration with chemical fertilizers. The objective of this article is to review recent advances in green manuring practice, in the context of potential benefits and drawbacks in use of this practice for annual crop production and sustain soil health and fertility.

Keywords::

• Carbon-nitrogen ratio
• dinitrogen fixation
• legume crops
• N mineralization

Notes

¹Values are averages of two field experiments.

¹Values are averges of three crops grown in rice-bean rotation.

∗,

∗∗ Significant at the 0.05 and 0.01 probability levels, respectively. Within same column, means followed by the same letter do not differ significantly at the 05 probability levels by Tukey's test.

²Cerrado soil fertility levels for rice were low (without addition of fertilizers); medium (50 kg N ha^{− 1}, 26 kg P ha^{− 1}, 33 kg K ha^{− 1}, 30 kg ha^{− 1} fritted glass material as a source of micronutrients); high (all the nutrients were applied at the double the medium level). Cajanus cajan L . was used as a green manure at the rate of 25.6 Mg ha^{− 1} green matter. For common bean the fertility levels were low (without addition of fertilizers); medium (35 kg N ha^{− 1}, 44 kg P ha^{− 1}, 42 kg K ha^{− 1}, 30 kg ha^{− 1} fritted glas material as a source of micronutrients) and high (all the nutrients were applied at the double the medium level).

³Varzea soil fertility levels for rice were low (without addition of fertilizers); medium (100 kg N ha^{− 1}, 44 kg P ha^{− 1}, 50kg K ha^{− 1}, 40 kg ha^{− 1} fritted glass material as a source of micronutrients); and high (all the nutrients were applied at the double the medium level). Cajanus cajan L. was used as a green manure at the rate of 28 Mg ha^{− 1} green matter. For common bean the fertility levels were low (without addition of fertilizers); medium (35 kg N ha^{− 1}, 52 kg P ha^{− 1}, 50 kg K ha^{− 1}, 40 kg fritted glass material as a source of micronutrients) and high (all the nutrients were applied at the double the medium level).