Effects of millet stover residue (0,500, and 2000 kg ha-') on wind erosion and surface soil properties were determined from 1991 to 1993 at the ICRISAT Sahelian Center in Niger, West Africa. Soil flux 0.1 m above the ground was significantly reduced with 2000 kg ha-' residue but not with 500 kg ha-'. Topographic measurements indicated that soil removed from the soil surface was less with either residue level than in the control. After 2 y, the soil surface (O-0.01 m) of both residue treatments had less coarse sand than the control, but more fine sand and clay, more organic carbon and an increased cation exchange capacity. The organic-C content of blown material was greater than that of surface soil. An amount of 500 kg ha-' residue can be considered useful for soil conservation, but 2000 kg ha-' are required for a significant reduction of soil flux caused during severe wind erosion events.

Wind erosion is regarded as a major contributor to the desertification process in the Sahel, yet little quantitative information is available for that region on soil losses by wind erosion under different land management practices. A 3‐yr, on‐farm experiment was, therefore, set up to assess the effect of ridging and either banded or broadcast millet stover mulches (2000 kg ha−1) on soil loss in a millet‐cowpea intercrop. For wind directions approximately perpendicular to the orientation of ridges and residue bands, sediment mass balances were calculated from the change in horizontal sediment mass fluxes measured across the experimental plots with Big Spring Number Eight sand traps. Mass balance calculations for 16 events over 3 yr indicated an average soil loss of 17.5, 15.4, and 18.0 Mg ha−1 on control plots, and deposition of 15.5, 15.3, and 7.4 Mg ha−1 on banded residue plots in 1995, 1996, and 1997, respectively. Broadcast and banded residue mulches were not significantly different (P = 0.05) in terms of their sediment trapping efficiency. During the same time period, ridges reduced soil losses by an average of 57% compared with the control plots, but their efficiency was reduced to less than 15% after 100 mm of cumulative rainfall as ridges collapsed. Linear regression analysis using the incoming sand fluxes as the independent variable was used to estimate potential soil losses for all events with sediment fluxes <25 kg m−1 irrespective of wind direction. The calculations indicated potential soil losses of up to 79 Mg ha−1 on control plots and deposition of 41 Mg ha−1 on broadcast residue plots in a single year. For wind erosion control, broadcast millet stover mulching constituted the most effective control technique because it effectively protected the soil against erosion and its trapping efficiency is expected to be independent of wind direction.

In the Sahelian zone of Niger, there is a need to develop guidelines for integrated nutrient management, which relies on the potential nutrient sources of manure, pearl millet residue and mineral fertilizers. A fully factorial on-station experiment was conducted during the 1994 and 1995 rainy seasons at Sadoré, Niger, combining application of: (i) broadcast millet residue (300, 900 and 2700 kg ha −1 ), (ii) broadcast cattle manure (300, 900 and 2700 kg ha −1 ) and (iii) mineral fertilizer (unfertilized control, 15 kg N ha −1 + 4.4 kg P ha −1 and 45 kg N ha −1 + 13.1 kg P ha −1 ). Manure and fertilizer increased millet yields in both years whereas residue was effective in 1995 only. The effect of manure and residue were additive, as was the effect of manure and fertilizer but only up to 50 kg N ha −1 . However in 1995, the response to fertilizer was approximately doubled in the presence of 900 or 2700 kg residue ha −1 compared to fertilizer with 300 kg ha −1 residue, indicating a strong synergistic effect. This synergistic effect was reflected in the partial factor productivity of nitrogen and phosphorous in both years. Two treatment combinations stand out as particularly relevant based on yield, partial factor productivity and nutrient balance criteria: 2700 kg manure ha −1 combined with (i) 300 kg residue and no fertilizer (95% grain yield increase); (ii) 900 kg residue ha −1 and 15 kg N + 4 kg P ha −1 (132% grain yield increase). There is a need for similar, long-term experiments to confirm the present results.

S c o p e of t h e j o u r n a l Agricukural and Forest Meteorology is an international journal for the publication of articles and reviews in the interdisciplinary fields of meteorology and plant, animal and soil sciences as applied to heat, mass and momentum transfer in agriculture, forestry or natural ecosystems. Articles must appeal to an international audience. Emphasis is on basic and applied scientific research to problems in agriculture, forestry and natural ecosystems. Theoretical models should always be tested against experimental data. Typical topics include radiation transfer in plant canopies, evapotranspiration, energy transfer, air turbulence i n and above plant canopies, forest-fire/weather interactions, pollutant fluxes to vegetation in the field and enclosures, trace gas fluxes in man-made and natural ecosystems, climatology of plant distributions, glasshouse energy balances and climatology, animal biometeorology. Special issues devoted to single topics, conference proceedings and comprehensive reviews are also published. P u b l i c a t i o n schedule a n d s u b s c r i p t i o n i n f o r m a t i o n Agricultural and Forest Meteorology will have flve volumes in 1993. The subscript~on for 1993 1000 A€ Amsterdam). Annual subscription price in the USA US $1 003 (subject t o change). including air speed delivery. Application t o mail st second class postage rate is pendin at Jamaica,

Soil fertility and climate risks are hampering crop production in the Sahelian region. Because experiments with only a few fertility management options on a limited number of sites and years cannot fully capture the complex and highly non-linear soil-climate-crop interactions, crop growth simulation models may suitably complement experimental research to support decision making regarding soil fertility and water management. By means of a long term (23 years) scenario analysis using the Agricultural Production Systems Simulator (APSIM) model, this study investigates millet response to N in view of establishing N recommendations better adapted to subsistence smallholder millet farming in the Sahel. Prior to this, the APSIM model was tested on a rainfed randomized complete block experiment carried out during the 1994 and 1995 cropping seasons, having contrasting rainfall conditions. The experiment combined, at three levels each, the application of cattle manure (300, 900 and 2700 kg ha −1), millet residue (300, 900 and 2700 kg ha −1) and mineral fertilizer (unfertilized control, 15 kg N ha −1 + 4.4 kg P ha −1 and 45 kg N ha −1 + 13.1 kg P ha −1) at ICRISAT Sahelian Center, Niger. The model suitably predicted plant available water PAW and the simulated water and nitrogen stress were in agreement with measurement (water) and expectation (N) regarding the fertilizer and rainfall conditions of the experiment. APSIM simulations were in satisfactory agreement with the observed crop growth except for the highest crop residue application rates (>900 kg ha −1). For biomass and grain yield, the model performance was relatively good in 1994 but biomass yields were slightly overpredicted in 1995. The model was able to adequately reproduce the average trend of millet grain yield response to N inputs from manure and fertilizer, and to predict the overall observed higher grain yield in 1995 compared to 1994, despite the better rainfall in 1994. The 23-year, long term scenario analysis combining different application rates of cattle manure, millet residue and mineral fertilizer, showed that moderate N application (15 kg N ha −1) improves both the long term average and the minimum yearly guaranteed yield without increasing inter-annual variability compared to no N input. Although it does imply a lower average yield than at 30 kg N ha −1 , the application of 15 kg N ha −1 appears more appropriate for smallholder , subsistence farmers than the usual 30 kg N ha −1 recommendation as it guarantees higher minimum yield in worst years, thereby reducing their vulnerability.