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close this bookAbstracts on Sustainable Agriculture (GTZ; 1992; 423 pages)
Open this folder and view contentsAbstracts On Traditional Land-Use Systems
Open this folder and view contentsAbstracts on farming systems research and development
Open this folder and view contentsAbstracts on integrated systems
Open this folder and view contentsAbstracts on cropping system
Open this folder and view contentsAbstracts on agroecology
Open this folder and view contentsAbstracts on agrometeorology
Open this folder and view contentsAbstracts on agroforestry
Open this folder and view contentsAbstracts on homegardens
Open this folder and view contentsAbstracts on seed production
Open this folder and view contentsAbstracts on plant protection
Open this folder and view contentsAbstracts on water management
close this folderAbstracts on soil fertility
View the documentAcknowledgements
View the document1. Soil constraints on sustainable plant production in the tropics.
View the document2. Impact of agricultural practices on soil pollution.
View the document3. The use of organic biostimulants to help low input sustainable agriculture.
View the document4. Nitrogen cycling in high-input versus reduced-input arable farming.
View the document5. Green manure in rice farming.
View the document6. Role of green manure in low-input farming in the humid tropics.
View the document7. Green manuring with vetch on acid soil in the highland region of Rwanda.
View the document8. Tropical lowland rice response to preceding crops, organic manures and nitrogen fertilizer.
View the document9. Pearl millet and cowpea yields in sole and intercrop systems, and their after-effects on soil and crop productivity.
View the document10. Influence of some characteristics of bean seed and seedlings on the tolerance to low phosphorus availability in the soil. (Infuencia de algunas caracteristicas de las semillas y plantulas de frijol Phaseolus vulgaris L. sobre la tolerancia a la baja disponibilidad de fósforo en el suelo )
View the document11. Evaluation of diverse effects of phosphate application on legumes of arid areas.
View the document12. Effect of n and p fertilizers on sustainability of pigeonpea and sorghum systems in sole and intercropping.
View the document13. Efficient fertilizer use in acid upland soils of the humid tropics.
View the document14. Vesicular-arbuscular mycorrhiza management.
View the document15. Impact of tropical va mycorrhizae on growth promotion of cajanus cajan as influenced by p sources and p levels.
View the document16. Benefit and cost analysis and phosphorus efficiency of va mycorrhizal fungi colonizations with sorghum (sorghum bicolor) genotypes grown at varied phosphorus levels.
Open this folder and view contentsAbstracts on erosion and desertification control
Open this folder and view contentsAbstracts on potential crops for marginal lands
 

4. Nitrogen cycling in high-input versus reduced-input arable farming.

Netherlands J. of Agric. Sc., 38, 1990, pp. 265-282

In this paper, N1-balance calculations covering the growing season will be discussed as well as changes in soil N mineralization rate, in N uptake by the crop, and in N losses due to changes in management. A conventional farming system was compared with two integrated systems, each system with the same rotation of winter wheat, sugar beet, spring barley and potatoes on a silt loam soil. Soil physical conditions and meteorological data necessary to account for some of the differences in overall N budget are discussed.

Field work was carried out at an experimental farm on a calcareous silt loam soil.

A previous experiment at the experimental site, in which three different input regimes of organic matter were compared, was taken as a starting point.

Agroecosystems are inherently more 'leaky' than undisturbed natural ecosystems where vegetation is continuously present. Increased inputs of nitrogen into agriculture have greatly increased crop (N) outputs, but they have also increased N losses to the environment.

Integrated management might give lower crop yields than conventional management, but because of lower costs, the profitability to the farmer could be similar.

Nitrogen balance sheets for the growing seasons of 1986-1988 showed N deficits of 0-170 kg ha-1, suggesting substantial N losses to the environment.

The uncertainty about actual N losses mainly depended on the uncertainty of estimated net N mineralization. Periods with much rainfall in 1987 and 1988, inappropriate use of animal manure and soil compaction may partly account for the heavy N losses in all farming systems. Potential rates of N-cycle processes were studied over the years to observe effects of changes in management.

The following conclusions can be drawn from these studies:

 

- The uncertainty about actual N losses mainly depended on the uncertainty in the calculated net N mineralization for field conditions. Especially uncertain was the contribution of the layer 40-100 cm, with a rather high organic matter content, to N supply of the crops.

- The soil organic matter and total-N contents showed a tendency to differentiate from their original two levels, into four levels as a result of changes in management. The next years will show which new steady-state levels will eventually result from integrated or conventional management.

- Correlations between N mineralization rates and biomass-N flush of soil samples were found to be situation-dependent.

- On fields with initial organic matter levels of 2.2% and 2.7%, crop yields under integrated management were on average 83% and 88%, respectively, of crop yields under conventional management.

- In the integrated system, the spring application of pig manure had to be changed to autumn application of spent mushroom compost, to prevent N loss by NH3 volatilization and by denitrification. The use of compost is also needed to maintain a high level of soil organic N.

- To minimize the risk of N losses to the environment, soil inorganic N concentrations should be kept low, especially in periods when no active crop is present and N losses are most likely to occur.

1241 92 - 12/67

Soil fertility

Review, symposium, rice farming, green manure, cropping systems

IRRI

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