Staggering planting dates is also a way farmers who lack farm labor use family labor more efficiently. Increased rainfall variability, especially at the onset of the season has led to staggered planting by farmers to spread the risk of total failure from a single planting date choice. Increasing variability in climate ( Laux et al., 2009) has also confounded the problem of low fertility, making investments into inputs and innovative technologies less attractive to smallholders ( Hansen, 2005). Low soil fertility, is therefore one of the major constraints. With increased nitrogen application of 90 kg N ha −1 or more under good rainfall, maize yields in northern Ghana reached 4500 kg ha −1 ( Naab et al., 2015). Despite these efforts, maize yields continue to be low, ranging from 800 to 1800 kg ha −1 without and with fertilizer application ( Ragasa et al., 2014). Over the past few decades, however, maize ( Zea mays), a major staple crop largely cultivated in southern Ghana has now been extended to the northern regions, due to breeding efforts that target yield response to small amounts of fertilizer among others.
This, apparently is due to their hardiness and ability to withstand low soil fertility and poor water holding capacity ( Singh and Singh, 1995) of the dominantly Low Activity Clay (LAC) soils. The northern regions of Ghana, and indeed the Sahel zones of West Africa have traditionally been home to the small grain cereals such as millet and sorghum. The use of ENSO-based targeted planting date choice together with modest fertilizer and manure application has the potential to improve maize yields and also ensure sustainable maize production in parts of northern Ghana. It was also observed that the addition of manure and fertilizer improved soil water and nitrogen use efficiency, respectively, and minimized yield variability, especially when combined with weather forecast. In Wa for instance, early optimum planting dates were associated with La Nina and El Niño (Julian Days 130-150 early May to late May) whereas late planting (mid June to early July) was associated with the Neutral ENSO phase. For three out of four locations, the ENSO-predicted optimum planting dates resulted in significantly higher maize yields than the conventional farmer selected planting dates. It could be shown that the optimum planting date for a given year was predictable based on February-to-April (FMA) Sea Surface Temperature (SST) anomaly for the locations with R 2 ranging from 0.52 to 0.71. In this study we used the DSSAT crop model to assess integrated water and soil management strategies that combined the pre-season El-Niño-Southern Oscillation (ENSO)-based weather forecasting in selecting optimal planting time, at four locations in the northern regions of Ghana. Maize yield in the northern Ghana is hampered by three major biophysical constraints, namely, poor soil fertility, low soil water storage capacity and climate variability. Through breeding and other crop improvement efforts, the zone of cultivation of maize has now extended to the northern regions of Ghana which, hitherto, were the home to sorghum and millet as the major cereals. Maize ( Zea mays) has traditionally been a major cereal staple in southern Ghana. 4R4D Unit, International Institute of Tropical Agriculture, Ibadan, Nigeria.3Department of Crop Science, University of Ghana, Legon, Ghana.2Department of Soil Science, University of Ghana, Legon, Ghana.1Soil and Irrigation Research Centre, University of Ghana, Kpong, Ghana.
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