Improving nutrient use efficiency from decomposing manure and millet yield under Plinthosols in Niger

To improve synchronicity between nutrients released from the decomposing manure with millet nutrient requirement under zaï technique, a 2-year field experiment was conducted at the International Crops Research Institute for the Semi-Arid Tropics Research Station, Sadoré, Niger. The treatments consisted of factorial combination of two rates of cattle manure (200 and 300 g per zaï hole), three periods of manure application (before planting, at planting and 15 days later) and two rates of mineral fertilizer [nitrogen (N), phosphorus (P) and potassium (K) 15–15–15] applied at 6 g per zaï hole and a control, without mineral fertilizer). Manure dry mass losses did not significantly differ among manure application periods in 2013. However, in 2014 the highest manure dry mass loss occurred when manure was applied before planting with 70% of manure applied being decomposed at millet maturity stage (115 days after litterbag installation) followed by manure applied at planting with almost 50% of dry mass losses. The quantities of N and P absorbed by millet at tillering stage represented, 61, 52 and 33% of N released and 15, 12 and 15% of P released at the same time when manure was applied before planting, at planting and 15 days after planting, respectively. Application of manure before planting increased on an average millet grain yield by 16 and 20% and N utilization efficiency by 25 and 31% compared to application of manure at planting and 15 days after planting respectively. Addition of mineral fertilizer induced a synergetic effect on millet grain yield (p = 0.002). Millet grain yields increased on average by 5, 17 and 57% when 6 g per zaï pit of NPK fertilizer were added to plots receiving manure application before planting, at planting and 15 days after planting, respectively. We conclude that application of manure prior to planting satisfies better millet nutrients demand, thereby increasing nutrient use efficiency and grain yield under zai pits

Watermelon production on stored rainwater in Sahelian sandy soils

Watermelon [Citrullus lanatus (Thumb) Matsun and Nakai ] is an important cash crop in West Africa where it is cultivated under rainfed conditions. The objective of this work was to identify best cultural practices for production of watermelons in the Sahel on stored rainwater in acid sandy soils. The experiments were carried out at the ICRISAT Sadore research center in Niger during two consecutive dry seasons, 2003 - 2004 and 2004 - 2005. Three soil management treatments were applied: microcatchments (also called half-moons), planting pits (also called zaï) and sowing on flat land. Each of these three treatments came with and without a soil amendment comprising of 500 g of manure mixed with 24 g of a complete (NPK) fertilizer (15-15-15) individually applied to each planting hill. Two watermelon cultivars were tested: ‘Malali’ and ‘Kaolack’. In each of the two years the experiments were sown on the 1st and on the 21st of September. Fruit and biomass yield, fruit Total Soluble Solids (TSS), days to fruiting and harvesting were determined. Soil fertility, root development and other physiological parameters were monitored to explain some of the differences between treatments. Soil amendments increased marketable yields from 1.3 to 3.5 tons ha-1 on average. Marketable yields at the first planting date were double the yields of the second planting date (3.2 vs. 1.6 tons ha-1). Yield differences were due to changes in fruit number not in fruit weight. Deep placement of soil amendments resulted in significant root development in deeper soil layers. Highest watermelon yields were achieved when sowing the Malali cultivar in amended planting pits on September 1st giving a yield of 8.2 tons ha-1

Impact of depth of placement of mineral fertilizer micro-dosing on growth, yield and partial nutrient balance in pearl millet cropping system in the Sahel

A study was carried out in the rainy seasons of 2008 and 2009 in Niger to investigate the effects of fertilizer micro-dosing on root development, yield and soil nutrient exploitation of pearl millet. Different rates of diammonium phosphate (DAP) were applied to the soil at different depths and it was found that although micro-dosing with DAP increased grain yield over the unfertilized control to a similar level as broadcast DAP, doubling the micro-dosage did not increase it further. Increasing the depth of fertilizer application from 5 to 10 cm resulted in significant increases in root length density, and deep application of fertilizer resulted in higher yields, although the increases were generally not significant. It was postulated that the positive effect of micro-dosing resulted from better exploitation of soil nutrients because of the higher root volume. Levels of nutrients exported from the soil were at least as high in plants receiving micro-dosing as the unfertilized control, and plants receiving microdosing exported 5–10 times more phosphorus from the soil than the amount added through fertilization

Evaluation of the Indigenous Use of the Weed Sida cordifolia L. in the Sahelian Zone of West Africa

Most farmers in Niger live below the poverty line and require low-capital intensification to improve agricultural production. The purpose of this study was to evaluate local knowledge on less beneficial weed for future use in managing the soil fertility of the Sahel region. Sida cordifolia was utilized in a scientific procedure to verify how local farmers utilize this species and the nature of the important roles behind this wild plant in terms of soil fertility management. The results of a questionnaire showed that S. cordifolia was less frequently used than other wild plants found in the same area, but that local farmers recognized this plant as one of the indicators of soil fertility in millet fields. The results of soil analysis also revealed a significant coefficient of variance in certain parameters such as total acidity and aluminum saturation of the soil, while multiple regression analysis showed the high influence of total acidity and soil pH on plant height and dry matter weight, respectively. These results indicate that the significant difference in plant growth of S. cordifolia was mainly due to soil acidity rather than soil fertility. The application of organic matter is one effective approach to resolve this problem and it was shown that the poor growth of S. cordifolia is a particularly useful marker to identify patches where organic matter should be applied. Despite its simplicity, this technique is considered particularly beneficial to allocate limited resources efficiently for sustainable, improved production

Contribution of previous legumes to soil fertility and millet yields in West African Sahel

Studies on combined effects of 4 legume crops residues and rock phosphate application on pearl millet yield were undertaken on sandy acid soil field from 2012 to 2015 at ICRISAT Sahelian center (ISC)-Sadore, Niger. The objective of the experiment was to assess the best combination of legume species x rate of crop residue x rock phosphate doses that can sustainably improve pearl millet yield in cereal monoculture system with a low input cost and minimum soil tillage. Over 3 years, the residual effect of previous legume crop residue significantly improved not only the grain yield (P<0.001) and dry residue yields (P<0.001) but also the growth parameters of pearl millet than millet mono-cropping. Treatments with or without natural rock phosphate did not show any statistical differences on millet yield while adding a micro dose of urea improved significantly the yield (P<0.001). The interaction effects of preceding legume crops in rotation with millet and restitution of dry residue on the earlier mentioned parameters across 3 years mono-cropping were studied in this experiment

Evaluation of groundnut genotypes for heat tolerance under field conditions in a Sahelian environment using a simple physiological model for yield

Heat tolerance of groundnut (Arachis hypogaea L.) was evaluated under field conditions using physiological traits identified in a yield model [crop growth rate (C), reproductive duration (Dr) and partitioning (p)]. In 1991, 625 diverse genotypes were initially screened under irrigation during the hottest months (February to May). Subsequent tests consisted of 16 contrasting genotypes selected based on a combination of high pod yield and partitioning coefficient of >0· 50. Large variation was observed among the 625 genotypes for pod yield and physiological traits. C was a powerful factor influencing pod yield. Eight genotypes combining high pod yield and a partitioning coefficient greater than 0·6 were identified. These included two released cultivars (55–437 and 796) in the Sahel. Correlations between seasons were significant for p (r=0·84), but non-significant for pod yield (r=0·40), C (r=0·39), and Dr (0·36). Date of sowing and genotypes had significant effects on pod yield and C, but were slight on p and Dr. Pod yield of most genotypes declined by more than 50% when flowering and pod formation occurred when maximum temperatures averaged 40°C. The results revealed that estimates of p would be a more reliable selection criterion for identification of genotypes tolerant to heat than yield. Further research is suggested to maximize crop growth rate and partitioning of genotypes growing under supra-optimal temperatures

Impact of previous legumes on millet mycorrhization and yields in sandy soil of West African Sahel

A preliminary study was conducted during the raining seasons 2012 through 2015 to assess the status of arbuscular mycorrhiza fungi associated with 4 legumes and millet on the sandy soil of Sadoré, Niger. A factorial completely randomized block design was used for the layout. Crop roots parameters of mycorrhization and soil fungi spore density and biodiversity were investigated as responses to varied planting densities, rates of rock phosphate, and of urea application on millet monoculture. Spores of Glomus were present in 100% of plots with respectively 96%, 47%, 77%, and 13% as relative frequency during rainy seasons 2012, 2013, 2014, and 2015; but spores of Gigaspora were present in 70% of plots and with 3.63%, 4%, 1.38%, and 1% as relative frequency the same years. Spore density/100g of root zone soil varied with crop species and rate of applied crop residue. The maximum intensity of mycorrhization was 78% while the arbuscular had a rate of 48% as maximum. The parameters of mycorrhization were influenced by the crop species but not by the rates of applied rock phosphate and the rate of returned crop residues as well. Millet yield in monoculture was affected by residual effects of previous basis legume crop

Fertilizer micro-dosing increases crop yield in the Sahelian low-input cropping system: A success with a shadow

Over the years, a scarcity of information on nutrient gains or losses has led to overemphasis being placed on crop yields and economic income as the direct benefits from fertilizer micro-dosing technology. There is increasing concern about the sustainability of this technology in smallholder Sahelian cropping systems. This study was designed in the 2013 and 2014 cropping seasons to establish nutrient balances under fertilizer micro-dosing technology and their implications on soil nutrient stocks. Two fertilizer micro-dosing treatments [2 g hill−1 of diammonium phosphate (DAP) and 6 g hill−1 of compound fertilizer Nitrogen-Phosphorus-Potassium (NPK) (15-15-15)] and three rates of manure (100 g hill−1, 200 g hill−1 and 300 g hill−1) and the relevant control treatments were arranged in a factorial experiment organized in a randomized complete block design with three replications. On average, millet (Pennisetum glaucum (L.) R.Br.) grain yield increased by 39 and 72% for the plots that received the fertilizer micro-dosing of 6 g NPK hill−1 and 2 g DAP hill−1, respectively, in comparison with the unfertilized control plots. The average partial nutrients balances for the two cropping seasons were −37 kg N ha−1yr−1, −1 kg P ha−1yr−1 and −34 kg K ha−1yr−1 in plots that received the application of 2 g DAP hill−1, and −31 kg N ha−1yr−1, −1 kg P ha−1yr−1 and −27 kg K ha−1yr−1 for 6 g NPK hill−1. The transfer of straw yields accounted for 66% N, 55% P and 89% K for removal. The average full nutrient balances for the two cropping seasons in fertilizer micro-dosing treatments were −47.8 kg N ha−1 yr−1, −6.8 kg P ha−1 yr−1 and −21.3 kg K ha−1 yr−1 which represent 7.8, 24.1 and 9.4% of N, P and K stocks, respectively. The nutrient stock to balance ratio (NSB) for N decreased from 13 to 11 and from 15 to 12 for the plots that received the application of 2 g DAP hill−1 and 6 g NPK hill−1, respectively. The average NSB for P did not exceed 5 for the same plots. It was concluded that fertilizer micro-dosing increases the risk of soil nutrient depletion in the Sahelian low-input cropping system. These results have important implications for developing an agro-ecological approach to addressing sustainable food production in the Sahelian smallholder cropping system

Determinants of fertilizer microdosing-induced yield increment of pearl millet on an acid sandy soil

Recent studies have reported the benefits of fertilizer microdosing in increasing crop yields in low input cropping systems. Little information is however available on the mechanisms underlying this effect. The objective of this study was therefore to explore the root-based mechanisms governing the growth enhancing phenomena of the fertilizer microdosing technology. A two-year experiment was conducted at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Research Station in Niger. Four treatments comprising (i) 2 g hill−1 of diammonuim phosphate (DAP), (ii) 6 g hill−1 of compound fertilizer NPK, (iii) broadcasting of 200 kg ha−1 of compound fertilizer NPK (recommended rate) and (iv) unfertilized control was arranged in a randomized complete block design with four replications. On average, fertilizer microdosing treatments (2-g DAP hill−1 and 6-g NPK hill−1) achieved 86% and 79% of the grain yields recorded from broadcasting of 200-kg NPK ha−1, respectively, in 2013 and 2014. The leaf area index and leaf chlorophyll content significantly increased with fertilizer microdosing at the early stage of millet growth. At the same stage, fertilizer microdosing enhanced the lateral root length density in the topsoil (0–20 cm) by 72% and 40% at respective lateral distances of 25 cm and 50 cm from the centre of the hill compared with broadcast of 200-kg NPK ha−1. Fertilizer microdosing did not significantly change soil pH in the root zone. It is concluded that the positive effect of fertilizer microdosing in increasing millet yield results from the better exploitation of soil nutrients due to early lateral roots proliferation within the topsoil