Erosion/productivity modelling of maize farming in the Philippine uplands. Part I: Parameterising the Agricultural Production Systems Simulator

This paper describes the parameterisation of the Agricultural Production Systems Simulator (APSIM) model to simulate open-field farming and intercropping of maize with leguminous shrub hedgerows. Whenever possible, parameters for the model were determined from measured or standard values for the environment of the field trials, while other parameters were derived from previous modelling experience in tropical environments. The remaining parameters were derived using step-wise calibration, where one or two parameters were calibrated against closely related measured data. Once parameterised, APSIM gave acceptable predictions of maize yields and soil loss from open-field farming and hedgerow intercropping. The version of APSIM described in this paper is used to simulate maize yields and soil erosion from open-field farming and hedgerow intercropping in the second paper in this series (Nelson et al., this issue). In the third paper, Nelson et al. (this issue) use cost–benefit analysis to compare the economic viability of hedgerow intercropping relative to traditional open-field farming of maize in relatively inaccessible upland areas

Erosion/productivity modelling of maize farming in the Philippine uplands. Part II: Simulation of alternative farming methods

A version of the Agricultural Production Systems Simulator (APSIM) capable of simulating the key agronomic aspects of intercropping maize between legume shrub hedgerows was described and parameterised in the first paper of this series (Nelson et al., this issue). In this paper, APSIM is used to simulate maize yields and soil erosion from traditional open-field farming and hedgerow intercropping in the Philippine uplands. Two variants of open-field farming were simulated using APSIM, continuous and fallow, for comparison with intercropping maize between leguminous shrub hedgerows. Continuous open-field maize farming was predicted to be unsustainable in the long term, while fallow open-field farming was predicted to slow productivity decline by spreading the effect of erosion over a larger cropping area. Hedgerow intercropping was predicted to reduce erosion by maintaining soil surface cover during periods of intense rainfall, contributing to sustainable production of maize in the long term. In the third paper in this series, Nelson et al. (this issue) use cost–benefit analysis to compare the economic viability of hedgerow intercropping relative to traditional open-field farming of maize in relatively inaccessible upland areas

Hydrology and soil erosion models for catchment research and management

In Maglinao, A. R.; Leslie, R. N. (Eds.), Soil erosion management research in Asian catchments: Methodological approaches and initial results - Proceedings of the 5th Management of Soil Erosion Consortium (MSEC) Assembly, held at Semarang, Central Java, Indonesia, 7-11 November 2000. Bangkok, Thailand: IWMI. Southeast Asia Regional Offic

Methodology for a multi-country study of soil erosion management

This paper describes the theoretical framework used in interpreting data on runoff and soil loss from field experiments to yield information on soil erodibility. This theory has been employed in the form of computer programs in the field experiments in various tropical countries and Australia which have collaborated in the Australian Centre for International Agricultural Research Project 8551 entitled “The Management of Soil Erosion for Sustained Crop Production”. The paper also describes common features of the experimental methodology employed in this project, including a description of the set of data management programs employed. These programs are used to retrieve electronically logged data, to field-check, summarise and compile these data in a form suitable for the analysis programs employed. Subsequent papers in this series illustrate application of the theoretical and experimental methodology outlined in this paper

Effects of increased temperatures and rice straw incorporation on methane and nitrous oxide emissions in a greenhouse experiment with rice

We investigated the effect of increased temperatures of water and soil, together with the incorporation of rice straw, on emissions of methane (CH4) and nitrous oxide (N2O), and the daily variation in CH4 emissions. Three temperature treatments (floodwater temperature), ambient, ambient +2°C and ambient +4°C, and two amounts of rice straw (0 and 6 t ha−1) were arranged in a randomized complete block design with four replications. The emissions of CH4 and N2O and the soil's redox potential (Eh) were measured weekly for two crop cycles. Daily variation in CH4 emission rates was measured with and without rice straw incorporation in planted and unplanted soil (with no warming treatments) during four growth stages of the crop. Methane emissions increased by as much as 91% with increasing amounts of water and soil temperature (+2 and +4°C), up to 34–35°C. Increases in temperature (+2 and +4°C above ambient) above 34–35°C decreased emissions by 30–36%. A decrease in soil Eh to < −100 mV and in CH4 emissions was observed earlier in the pots containing rice straw than in those without straw. Methane emissions varied daily; they were larger from 11:00 to 14:00 hours, particularly in unplanted soil. They showed positive correlations with the temperatures of both soil and air. In contrast, N2O emissions were negligible throughout the growing season. The emissions of CH4 evidently depend on the background temperature range; in our experiment, CH4 emissions increased up to 34°C and then they decreased above that

Erosion and productivity of vegetable systems on sloping volcanic ash-derived Philippine soils

Soil erosion is a significant threat to agricultural productivity on sloped lands. This paper assesses the effectiveness of several different soil conservation practices for vegetable systems on sloped volcanic ash-derived soils. A field experiment was conducted to test the authors' hypothesis that contouring, strip cropping, and high-value contour hedgerows (asparagus, pineapple, pigeonpea, and lemongrass) would reduce soil loss relative to the traditional up-and-down farming method. They found that up-and-down cultivation had the greatest annual soil loss, followed by high-value contour hedgerows, strip cropping, and contouring. For all test plots there was a large gradient in the soil characteristics and productivity between the upper and lower bounds of the plots; crop yields in the downslope sections were significantly higher. The contour hedgerow method caused rapid formation of bioterraces, which also showed much greater productivity in the bottom portion