Crop residue application increases nitrogen fixation and dry matter production in groundnut (Arachis hypogaea L.) grown on an acid sandy soil in Niger, West Africa

Field experiments were conducted during the rainy reasons of 1989, 1990 and 1991 on an acid sandy soil in Niger, West Africa, to assess the effect of millet straw application (+CR) on growth and N2 fixation of groundnut (Arachis hypogaea L.). Three years of +CR (4 t ha−1 yr−1) increased symbiotic N2 fixation, total dry matter production (haulm plus pods) by 83% and total nitrogen (N) accumulation by 100%. Concentration of N in the shoot dry matter and total N in the soil were only slightly affected by the +CR treatment. Crop residue application increased the concentration of potassium (K) and molybdenum (Mo) and decreased the concentrations of aluminium (Al) and manganese (Mn) distinctly, both in the plant (shoot and nodule dry matter) and in the soil. The increase in dry matter production and N uptake was mainly due to improved N2 fixation reflected by enhanced formation and growth of nodules as well as nitrogenase activity. This was attributed to improved chemical soil conditions, particularly to the higher availability of Mo and the lowered content of available Al and Mn. Although with the application of 4 t CR ha−1, 60 kg K were supplied, increased growth could not be attributed to the additional supply of K

Short- and long-term effects of crop residues and of phosphorus fertilization on pearl millet yield on an acid sandy soil in Niger, West Africa

Field experiments were conducted during the rainy seasons of 1990 and 1991 on an acid sandy soil (Luvic Arenosol) in Niger, to assess long-term (since 1986) andshort-term (since 1990) effectsof millet straw (cropresidues) at different amounts (2 t and 6 t ha−1) and modes of application (incorporation, mulching and burning), andofphosphorus (P) fertilization on dry matter yield of pearl millet [Pennisetum glaucum (L.) R. Br.]. Especially long-term, but also short-term application ofcropresidues increased dry matter yield of pearl millet by more than 60%, whereas their omission decreased yield immediately. Compared to mulching or burning, higher yields were obtained with incorporation ofcropresidues. When cropresidues were applied as mulch, dry matter yield was increased to the same extent by 2 t and 6 t ha−1. Similar dry matter yields were achieved with cropresidues (-P) to those with P fertilizer only. An additional yield increase could be obtained by simultaneous application ofcropresiduesand P. Without cropresidues, potassium (K) concentrations in the shoot dry matter indicated K deficiency. With cropresidues considerable amounts of K (15 kg t−1) were provided and raised the K concentrations in the plants to the sufficiency range. Although with cropresidues some P was provided (1.5 kg t−1), the beneficial effects were primarily attributed to increased P acquisition by the millet plants, which was reflected in enhanced root growth in the topsoil (0–10 cm

Towards understanding the traits contributing to performance of pearl millet open-pollinated varieties in phosphorus-limited environments of West Africa

Aims Pearl millet [Pennisetum glaucum (L.) R. Br.] open-pollinated varieties, which are the predominant cultivars, have never been systematically evaluated for adaptation to low-soil phosphorus (P), a major constraint on pearl millet production in West Africa (WA). Methods We evaluated grain yield (GY), flowering time (FLO), harvest index (HI), and residual grain yields (RGY) of 102 open-pollinated varieties from WA under low-P (−P) and high-P (+P) field conditions in six environments of WA. In addition, PE-related traits of the varieties were evaluated at early growth stage in a pot experiment. Results Significant genetic variation was observed for GY, FLO, HI and PE-related traits. P-efficient varieties had higher yield under −P conditions. Varietal performance under −P varied across environments depending on FLO, relative flowering delay under −P (FD) and RGY measured in the field. Low-P-susceptible varieties had higher FLO, lower HI than low-P-tolerant varieties. Response to direct selection under −P field conditions was 20.1 g m−2, whereas indirect selection response under +P was 16.3 g m−2. Conclusions Selection under −P field conditions while taking into account seasonal variations for FLO, FD and PE is expected to be important for improving GY specifically targeting −P environments in WA

Association analysis of low-phosphorus tolerance in West African pearl millet using DArT markers

Pearl millet [Pennisetum glaucum (L.) R. Br.] is a food security crop in the harshest agricultural regions of the world. While low soil phosphorus (P) availability is a big constraint on its production, especially in West Africa (WA), information on genomic regions responsible for low-P tolerance in pearl millet is generally lacking. We present the first report on genetic polymorphisms underlying several plant P-related parameters, flowering time (FLO) and grain yield (GY) under P-limiting conditions based on 285 diversity array technology markers and 151 West African pearl millet inbred lines phenotyped in six environments in WA under both high-P and low-P conditions. Nine markers were significantly associated with P-related traits, nine markers were associated with FLO, whereas 13 markers were associated with GY each explaining between 5.5 and 15.9 % of the observed variation. Both constitutive and adaptive associations were observed for FLO and GY, with markers PgPb11603 and PgPb12954 being associated with the most stable effects on FLO and GY, respectively, across locations. There were a few shared polymorphisms between traits, especially P-efficiency-related traits and GY, implying possible colocation of genomic regions responsible for these traits. Our findings help bridge the gap between quantitative and molecular methods of studying complex traits like low-P tolerance in WA. However, validation of these markers is necessary to determine their potential applicability in marker-assisted selection programs targeting low-P environments, which are especially important in WA where resource-poor farmers are expected to be the hardest hit by the approaching global P crisis

Phosphorus seed coating increases phosphorus uptake, early growth and yield of pearl millet (Pennisetum glaucum (L.) R. Br.) grown on an acid sandy soil in Niger, West Africa

In pot and field experiments conducted in 1990 and 1991 on an acid sandy, phosphorus (P) deficient soil in Niger, West Africa, the effect of seed coating on seedling emergence, early growth and grain yield of pearl millet (Pennisetum glaucum (L.) R. Br.) was studied. Seeds of pearl millet were coated with different rates (0; 0.5; 1.0; 2.0; 5.0; 10.0 mg P seed–1) and types of P fertilizers (single superphosphate, ammonium dihydrogen phosphate; monocalcium phosphate, sodium dihydrogen phosphate and sodium triphosphate). Seedling emergence was generally reduced at coating rates higher than 0.5 mg P seed–1 and prevented with single superphosphate and sodium triphosphate at rates higher than 5 mg P seed–1. No correlation was found between the pH and osmomolity of the coatings and final emergence of millet seedlings. The most favourable effect on plant growth and P content was achieved with ammonium dihydrogen phosphate (AHP) as seed coating. This was attributed to the enhancement effect of ammonium on P uptake. Compared to the untreated control dry matter production at 20 days after planting (DAP) was increased by 280%, P content per plant by 330%, total biomass at maturity by 30% and grain yield by 45%. Although seed coating with AHP may be harmful to seedlings emergence, it represents a suitable method to enhance early growth and increase yield of pearl millet