Ali Ibrahim

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.

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.

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

ABSTRACT 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.

Evaluation of five pearl millet varieties for yield and forage quality under two planting densities in the Sahel

In the Sahel that is typified by an agro-pastoral system and a long dry season between rains, the availability of animal feed is a very serious constraint. The objectives of this study were to identify pearl millet varieties with high forage productivity under rainfed conditions in the Sahel; to identify best planting densities and to find physiological mechanisms conducive to high forage productivity in pearl millet. The experiment was carried out at the ICRISAT Sadore Research Center in Niger during the 2006 rainy season. Five long duration varieties (Malgorou, Batchoudine, Sanioba, Yabo Maiwa and Somno Damari) as forage crops were compared at two planting densities (10,000 and 20,000 hills/ha). Dry matter yield and forage quality was assessed at the boot, anthesis and at the soft dough stages. The higher planting density gave in this year higher dry matter (and grain) yield than the lower density. The dough stage was the most suitable stage for harvest because dry matter was at its highest. However, organic matter digestibility and crude protein are higher at the boot stage compared with the dough stage. The Malgorou variety gave the highest dry matter yield at the dough stage (8.57 tons/ha at the high planting density). The high forage productivity of this variety was attributed to the longer growing period of time before anthesis and the bigger number of tillers. The results of this study demonstrated that long duration varieties of pearl millet can become an important source of forage in the Sahel under rainfed conditions.

Yields and forage nutritive quality of high-yielding dual purpose cowpea (Vigna unguiculata L. Walp.) varieties in the Sahelian low-input cropping system

Cowpea is a major food legume crop in the Sahel with tolerance to drought and to the nutrients-leached acid sandy soils of this region. However, the existing cowpea varieties grown by farmers are low yielding and pest sensitive which make them unsuitable to satisfy farmer’s needs. The objective of this study was to identify high-yielding cowpea varieties which are well adapted to the Sahelian ecosystem. Eight dual-purpose cowpea varieties from various sources were tested with and without insects control in Niger during two cropping seasons (2005 and 2007). In 2005, a relatively wet year, KVX 745-11-P and four other varieties (ISV 20, ISV 40, ISV 128 and IT98D-1399) gave highest grain yields ranging from 1220 to 1521 kg ha-1. In the dry year (2007), the highest grain yield was recorded with ISV 128. There were also significant differences in forage yield between varieties in both the wet and dry year. Application of insecticide increased cowpea grain yields significantly. Cowpea produced without insect control (spray) resulted in high grain yields losses and increased cowpea fodder yields in both years. KVX 745-11-P was the most sensitive variety to insects whereas IT98D 1399 seemed to be relatively the most insect tolerant variety. There were no significant differences between varieties in most forage quality parameters. These results provide the possibility of a potential extension of dual-cowpea varieties for improved food security in the Sahel. Keywords: Dual purpose cowpea, grain yield, fodder quality, sahel

Rain-Fed Plantations Of The Domesticated Ziziphus Mauritiana In The Sahel: Effects Of Varieties And Rootstocks On Yields And Fruit Quality

Abstract A long-term study was conducted to explore the possibility of using traditional rain-fed systems for growing domesticated Ziziphus mauritiana (so-called Pomme du Sahel) in the Sahel. Five varieties, Gola, Ben Gurion, Seb, Umran and Kaithli, were grafted on six rootstocks of Z. mauritiana from various agroecological zones of Niger. Trees were planted inside microcatchments at 8 × 8 m spacing. Over a period of six years, the variety Umran gave the highest fruit yield (3600 kg·ha−1) and the lowest fruit yield was documented for variety Seb (1970 kg·ha−1). Individual fruit weight ranged from 25.8 g for ‘Umran’ to 9.5 g for ‘Seb’. The rootstocks had no effect on average fruits yields and fruit size. There was a significant linear correlation between fruit yield and annual rainfall. In a rainy year (680 mm), the average yield of the five varieties was 7580 kg·ha−1. The results of the current study indicate that dry land plantations of Pomme du Sahel can guarantee food security during dry years in the Sahel. However, further studies are required to evaluate the economic feasibility of this system.