Maize response to chemical and microbial products on two Tanzanian soils

Open Access JournalLow soil fertility has been a major factor to low maize yields in smallholder farms in sub-Saharan Africa. Technologies have been proposed including inorganic, fertilizers and plant growth promoting microorganisms. A study was conducted under greenhouse and field conditions to evaluate the effects of liquid inorganic fertilizer and microbiological products on growth, nutrient uptake and yield of maize. Products evaluated were Teprosyn (nitrogen, zinc phosphorus), BioSoil Crop Booster (BSCB) (Pseudomonas fluorescens), and Bio Soil Nitro plus (BSN+) (Acetobacter sp.). Treatments were: products alone (low and high rate), product + half rate phosphorus (10 kg P ha-1), half rate P, full rate P (20 kg P ha-1) and Control. All products were analysed for quality. None of the products met the label claims in nutrient/organism concentration. An increase of biomass was observed in the greenhouse for half rate P + BSCB low rate and high rates for BSCB and BSN+ compared to Control. Half rate P + BSN+ low rate gave the highest grain yield which was similar full rate nitrogen and P. BSCB and BSN+ at low rates with P half rate resulted in an increase in biomass yield in the greenhouse. Efficacy of low rate BSN+ + half rate P was demonstrated when applied at the recommended rates and combined with half rates of N and P. A package of inorganic and Bio-fertilizers should be developed based on soil fertility status, and the quality of the inputs verified to ensure that they are conform to the label guarantee analysis

Trees, soils, and food security

Trees have a different impact on soil properties than annual crops, because of their longer residence time, larger biomass accumulation, and longer-lasting, more extensive root systems. In natural forests nutrients are efficiently cycled with very small inputs and outputs from the system. In most agricultural systems the opposite happens. Agroforestry encompasses the continuum between these extremes, and emerging hard data is showing that successful agroforestry systems increase nutrient inputs, enhance internal flows, decrease nutrient losses and provide environmental benefits: when the competition for growth resources between the tree and the crop component is well managed. The three main determinants for overcoming rural poverty in Africa are (i) reversing soil fertility depletion, (ii) intensifying and diversifying land use with high-value products, and (iii) providing an enabling policy environment for the smallholder farming sector. Agroforestry practices can improve food production in a sustainable way through their contribution to soil fertility replenishment. The use of organic inputs as a source of biologically-fixed nitrogen, together with deep nitrate that is captured by trees, plays a major role in nitrogen replenishment. The combination of commercial phosphorus fertilizers with available organic resources may be the key to increasing and sustaining phosphorus capital. High-value trees, 'Cinderella' species, can fit in specific niches on farms, thereby making the system ecologically stable and more rewarding economically, in addition to diversifying and increasing rural incomes and improving food security. In the most heavily populated areas of East Africa, where farm size is extremely small, the number of trees on farms is increasing as farmers seek to reduce labour demands, compatible with the drift of some members of the family into the towns to earn off-farm income. Contrary to the concept that population pressure promotes deforestation, there is evidence that demonstrates that there are conditions under which increasing tree planting is occurring on farms in the tropics through successful agroforestry as human population density increases. <br

Fertiliser Trees for Sustainable Food Security in the Maize-Based Production Systems of East and Southern Africa

The negative effects of soil fertility depletion on food security, especially among smallholder farmers in Africa, is of economic importance, and may be worsened by climate change and rising global fertiliser prices. Substantial efforts and investment have gone into development of alternative soil fertility management options. These include vigorous research and development of N-fixing plants or “fertiliser trees”, that has been on-going in the last two decades in East and Southern Africa. In this paper, we review several studies conducted both on-station and on-farm and synthesise the results in terms of improvements in soil physical, chemical and biological properties, and crop yield in response to fertiliser trees. Our major findings are that (1) fertiliser trees add more than 60 kg N ha−1 per year through biological nitrogen fixation (BNF); (2) nutrient contributions from fertiliser tree biomass can reduce the requirement for mineral N fertiliser by 75%, translating to huge savings on mineral fertilisers; (3) fertiliser trees were also shown to substantially increase crop yield. A meta-analysis has further provided conclusive evidence that with good management, fertiliser trees can double maize yields compared with local farmer practices of maize cultivation without addition of external fertilisation. (4) Financial analyses showed that fertiliser tree systems are profitable and also have higher net returns than the farmers’ de facto practice, i.e. continuous maize cropping without fertiliser. We conclude that widespread adoption and scaling up of fertiliser trees can reduce the amount of mineral fertiliser needed, maintain the soil ecosystem, and positively impact on the livelihoods of farm households in southern Africa.www.agronomy-journal.or