Impact of Fertilizer Usage on Crop Productivity at Siguidolo

On a poor soil, fertilizers application is the best ways to meet crop need and restore the lost nutrients. However, its application is constrained in Mali due to the low access to fertilizers by smallholder farmers, resulting in low crop production. Today, make available to farmer’s fertilizer and information needed for its proper use is an essential asset for sustainable agriculture and food security. Before, assessing the existing fertilizer usage and it impact on yield is a prerequisite. A study was done to characterise fertiliser management practices at Siguidolo and assess the impact on millet and sorghum yields. Thus, normalized difference vegetation Index (NDVI) and visual interpretation were used to estimate vegetation cover as sources of organic matter (OM). Investigation was doneto get information about manure production and areas occupied by crop production. Geographic Information System and Survey was done to obtain information on fields, fertilizer used and yields. The results showed low vegetation cover (0.02 to 0.24) indicating low source of organic matter. The mean manure produced was 14373kg/ha/year while 69300kg was recommended. Organic fertilizers and integrated organic and mineral fertilizers occupied greater area. About 24.1% of the area did not received fertilizer. The extremely low fertility areas tended to receive more nutrient application. Indications are that, even in those areas where fertilizers were applied, the right quantities were seldom used. Low yield for millet and sorghum was recorded ranging from 414.66 kg ha to 703.80 kg ha for millet and 404.12 kg ha to 448.04 kg ha for sorghum. Keyword— Fertilizer, usage, crop, productivity, Siguidolo.


INTRODUCTION
One of the main factors limiting crop efficiency and food security in Mali is the low natural fertility of the soils and its continued decline over years of cultivation. The decline in soil fertility and low nutrient application is the leading cause of the declining per capita food production in Sub-Sahara Africa (Chianu, 2012;Bremanet al., 1983;Kihara et al., 2016;IFDC, 2006;Shapouri et al., 2010;Muller et al., 2012). Food production index per capita showed a declining trend over the last decades and about 29% of the population is estimated to be undernourished (FAO stat, 2008). To reverse this trend, it is important to replenish the removed nutrients which results from crop uptake, harvest, erosion and leaching. Fertilizers application is one of the best ways to meet crop need and restore the lost nutrients(Gatti et al. 2019). Fertilizersare any material of natural or synthetic origin which, when applied to soils, provide one or more nutrients essential to plants growth and yield (Barker,2019). They occupy a prominent position in food security challenges on poor soils (Stewarta et al., 2012). However, their application is severely constrained in Mali due to the low access to fertilizer (IFDC, 2015) by the poor smallholder farmers, resulting in low agriculture production. Today in Mali, make available to farmer's fertilizer and information needed for its proper use is an essential asset for promoting sustainable agriculture production and food security while preserving environment. Before, assessing the existing fertilizers usage and it impact on crop production and food security is a prerequisite in the identification and development of appropriate improved practice. The objective of this study was to characterise the existing fertilisers management practices at Siguidolo and assess their impact one millet and sorghum yield in order to develop an improved method.

Study site
Siguidolo is located in Segou region of Mali in a depression surrounded by the plateaux. It is between -6.80399 o and -6.78583 o N and 12.91624 o and 12.91229 o W. The mean annual rainfall is 700 mm. Soils are mostly sandy loam. During the rainy season, interrill (sheet) erosion is common with intermittent rills and gullies, some of which measure up to 1.0 m deep in the relatively hilly sites. In the depressions and valleys, particularly along the streams, waterlogged conditions often prevail during the rainy season presumably due to high water table.
2.2 Vegetation cover mapping Normalized Difference Vegetation Index (NDVI) calculation and visual interpretation were used on a Quick bird image covering the study site at about 75%. NDVI is the dimensionless index that is indicative of vegetation density and is calculated by comparing the visible and near-infrared sunlight reflected by the plant surface (reflectance). The vegetation Index was used to quantify the density of green leaf vegetation by the formula: When NDVI calculation is applied on an image or a pixel, the output gives a value ranging between minus one (-1) to plus one (+1). A zero value means no green vegetation and close to +1 (0.8 -0.9) indicates the highest potential density of green leaves. The spatial distribution and the density of vegetation have significant implications on fertilizer practices in an area. The map derived from NDVI calculation was used for ground verification. Visits were done on various locations of the study area to identify and characterise known and unknown features marked on the map.

2.3
Assessment of organic manure production capacity Investigation was donebeside the households to get information about manure production capacity and the area occupied by agriculture. Dembele (1994) showed that, the average organic manure production by livestock was 153.5 kg/head/4 months in rainy season and 182 kg/head/4 months in dry season. These data and the number of livestock were used to calculate the average organic manure production during both seasons at Siguidolo. Data were then used to estimate the availability of organic manure per year.

2.4
Fertilizer practices mapping Global Positioning System (GPS) was used to delimit farmers' fields. Survey was done to obtain information on the fertilizer practices used in each field. Then, GPS and survey data were combined in Geographic Information System (GIS) environment to map fertilizer practices.

2.5
Assessment of the impact of fertilizer practices on yield Survey was conducted beside the households to found out information about the ways of fertilizer usage (spread or micro-dosing, etc.), the types and amounts of fertilizers used, and yields obtained on the sorghum (Sorghum bicolor L. Moench) and millet (Pennisetumglaucum) fields. 36 out 38 households were interviewed.

Vegetation cover mapping
Vegetation assessment resulting from NDVI processing is presented in Fig.1   Organic manure production capacity is presented in Table2. Organic manure production was high in dry season. The highest amount of organic manure was produced by bovine.

Fertilizer practices mapping
Fertilizer's practices data collected on the site was overlaid on the soil fertility status map (Fig. 2) in order to understand the link between soil fertility status and farmer's fertilizers application decision. The fertility status varied from low, to extremely low. The very low status covered the greater area. Their respective area of coverage was 42.54 ha (4.81%), 134.9 ha (15.26%) and 706.61 ha (79.93%). Organic fertilizer (OF). The extremely low fertility area tended to receive more nutrient application.

Fig.3: Spatial distribution of fertilizers usage at Siguidolo in 2013
Table4 shows the areal coverage of fertilizers. Organic fertilizers and integrated organic and mineral fertilizers occupied the greatest area of 333.51 ha over 506 ha. About 24.1% of the area did not received fertilizer.

Table.4: Areas covered by fertilizers in 2013.
Table5 shows the soil amendments applied in 2013 and percentage area of coverage. The very low fertility areas tended to receive more nutrient application.

Assessment of the impact of fertilizer practices on yield
Information on soil fertility status, spatial distribution of millet and sorghum grain yields is presented in Figures 4  and 5, respectively. The means millet grain yield was 414.66 kg ha -1 on soil with low nutrient status, 703.80 kg ha -1 on soil with very low nutrient status and 558.2 kg ha -1 on soil with extremely low nutrient status. The corresponding yields for sorghum were 445 kg ha -1 , 448.04 kg ha -1 and 404.12 kg ha -1 respectively. The very low and extremely low nutrient status soils were compensated by greater amounts of fertilizer application with a consequent higher grain yield than the relatively better low fertility soils. The percentage area of the low, very low and extremely low fertility status soils that received fertilizers were 44.4, 80.33 and 71.01 respectively.  /dx.doi.org/10.22161/ijeab.45.42  ISSN: 2456-1878 www.ijeab.com Page | 1565 IV. DISCUSSION Vegetation is source of organic matter (OM). OM has many beneficial effects soil (Erich et al., 2002;Sanyal et al., 1991). It improves the physical, chemical and biological properties of the soil.Thus, Maurice et al. (1998) used organic matter as an indicator of soil fertility, overall soil stability and a factor influencing the reduction of soil erosion, soil compaction and bulk density (Vorhees, W.B. 1992). Fen-Li (2006) found that the vegetation effect on soil erosion was predominant.As Soil Organic Matter increases, the quantities of N, P, K available, carbon and certain micronutrients increase (Oates, 1998, Dembele, 2017. Acquaye (1990) reported that organic matter was the main source of N, P and S for plant growth in small farms without fertilizer. Nitrogen (N) use in crop production is inevitable target (Rossner et al. 2014).In addition, soil water infiltration is more influenced by vegetal cover and soil organic matter(Sampaiode Almeida, et al., 2018)as well as nutrient and water holding capacities (Lal et al., 1998, Traore, 2003Morgan, 2005; Barmani et al., 2013). They improvesoil microorganism activities (Havlin et al., 2005),soil aeration,plant root growthand elongation and pH stability.Furthermore, vegetation covers cushions the soil against the erosive forces of water and wind (Vásquez-Méndez et al., 2009,) and thereby reduce their detachment and transport capacities with a resultant reduction in erosion.Assessing the vegetation cover of the study site therefore became necessary. The effectiveness of vegetative cover in reducing erosion however depends, in part, on its density and spatial coverage, the continuity of the canopy and height (Nanko et al., 2008). NDVI at Siguidolo varied from -0.01 to 0.24 indicating low and sparse vegetation covert and very low source of organic matter. This condition has negative effects on soil fertility and influences fertilizer management strategies. Manure production capacity impacts soil fertility in Mali because small scale farmers don't own enough money to afford mineral fertilizer at the recommended level (Jens and al., 2007; PRSP, 2002). A mean of 11.06 cattle's, 7.61 sheep, 8.7 goats and1.19 donkeys per household was investigated in the site which produce 14373 kg/year of organic manure. This amount is not sufficient to meet a mean of 13.86ha/household measured in the area where 5t/ha is recommended.ExceptComplexes Cereal, the mean of the other mineral fertilizers used in the site was significantly below the recommended rate of 50 kg/ha of DAP and 50 kg/ha of Uréanoted byOuendeba (2010). Analysis has shown that the very low fertility area tended to receive more nutrient application. Indications are that, even in those areas where fertilizers were applied, the right quantities were seldom used. Sorghum and millet yields recorded in the study site were significantly low compared to 1424 kgha -1 and 1301 kg ha -1 for millet in 2013 and 2014, respectively and 1378 kg ha −1 for sorghum in 2014 harvested in research station by Traore et al. (2017). Increasing Crop production and productivity atSuigidolo area, dominated by smallholder farmers require a set of accompanying soil conservation and efficient water utilization technologies.Sound soil fertility management, as recommended by Quansah (2000), should therefore use available livestock and poultry manure and crop residues wherever practical, taking appropriate nutrient credit for these materials and using mineral fertilizers to balance the crops nutritional requirements for realistic yield goals. These include ridge furrow system, tie-ridging, circular contour bunds, zai, cereal legume rotations and residue management. In contributing to this effort, the cropping systems in the area need to be study to show trends as a basis for recommending asustainable cropping systemable to improve the biophysical and socio-economic conditions of the farmers.

V.
CONCLUSION Agriculture development at Siguidolo involves the improvement of organic matter production, andthe adapted agriculture technologies.