P. S. Hammes

Effects of Farmyard Manure and Inorganic Fertilizers on Sorghum Growth, Yield, and Nitrogen Use in a Semi-Arid Area of Ethiopia

ABSTRACT A field experiment was conducted to assess the effect of the combined use of farmyard manure and inorganic fertilizer on the growth and yield of sorghum and on soil chemical properties in a semi-arid area in northeastern Ethiopia. Twelve treatments comprising factorial combinations of four levels of farmyard manure (0, 5, 10, and 15 t ha−1) and three levels of inorganic fertilizers (0%, 50%, and 100% of the recommended rate) were compared in a randomized complete block design with three replications over a period of six years. The results revealed significant improvements in the growth and yield of sorghum due to the main and interaction effects of farmyard manure and inorganic fertilizer application. The combined application of farmyard manure and inorganic fertilizers increased post-anthesis dry-matter production by 147%–390% and grain yield by 14%–36%. The main effects of farmyard manure and inorganic fertilizers increased stover yield by 8%–21% and 14%–21%, respectively. Farmyard manure application increased total nitrogen (N) uptake by 21%–36%, grain protein yield by 8%–11%, and grain protein concentration by 20%–29%. Application of farmyard manure along with 50% of the recommended inorganic fertilizer rate resulted in a grain yield equivalent to, or greater than that for 100% of the recommended inorganic fertilizer rate, thus effecting a 50% savings of inorganic N and phosphorus (P) fertilizer. Application of 5, 10, and 15 t farmyard manure ha−1along with 100% of the recommended fertilizer rate and 5, 10, and 15 t farmyard manure ha−1 along with 50% of the recommended fertilizer rate can be recommended for farmers who can and cannot afford to buy inorganic fertilizers, respectively.

The Role of Animal Manure in Sustainable Soil Fertility Management in Sub-Saharan Africa: A Review

ABSTRACT Sub-Saharan Africa contains soils that have been cropped for generations. Consequently, their inherent fertility has been severely depleted. In such soils, net negative balances of nutrients are a common problem. The current soil nutrient depletion rates are contributing towards decreasing crop yields. The search for sustainable soil fertility replenishment techniques is, therefore, an urgent need. A key resource in this respect is animal manure. Such manure can increase and maintain soil fertility by providing N, P, K, S, Ca, Mg, Na and other trace elements such as Fe, Mn, Cu, Zn. It also improves the pH of acid soils and calcareous soils, increases soil organic matter content and cation exchange capacity, improves soil aggregate stability, soil macro-structure, infiltration, water holding capacity and erosion resistance. However, animal manure cannot meet crop nutrient demand over large areas, because of the limited quantities available and the relatively low nutrient content of the materials. The combined use of animal manure and mineral fertilizers is, therefore, a promising alternative strategy for resource-poor small-scale farmers in Africa.

Localization of the photoperiodic perception in potatoes

SummaryIt was found that probably all the leaves of young potato plants played a part in perceiving the photoperiodic stimulus which induces tuberization. The importance of the mature leaves in the photoperiodic perception is emphasized by the large tuber yield which could be obtained by subjecting these leaves to inductive photoperiods while the growing tip and young leaves were subjected to non-inductive photoperiods. Tubers were produced under non-inductive photoperiods when the young leaves and meristematic stem apices were removed. Tuberization in these plants could be inhibited by application of gibberellic acid. The developing leaves, therefore, seem to produce a substance, probably gibberellin, which prevents tuberization under long-day conditions. If a specific tuberforming substance is involved it is present in active concentrations even under non-inductive photoperiods. The results are in agreement with the theory that a balance between endogenous gibberellins and another substance(s) controls tuberization.

Net photosynthetic rate of potato at high temperatures

SummaryPotato cultivars were grown in a glasshouse and plants periodically transferred to a growth chamber. When the ambient temperature in the growth chamber was raised from 15 to 40°C in steps of 5°C per hour, net photosynthetic rate decreased at temperatures above 20°C. At 40°C the rate was 37% of the rate at 20°C. A greater decrease in net photosynthetic rate occurred with plants of the cultivar Up-to-Date than with cultivars R100 and BP13. Low values of leaf diffusive resistance were recorded and changes in photosynthetic rate could not be explained by changes in this factor. When a constant ambient air temperature of 20°C was maintained while soil temperature was increased, net photosynthetic rate decreased.

Yield response of potato genotypes to different soil water regimes in contrasting seasons of a subtropical climate

SummaryPotato crops in subtropical climates are often subjected to water stress, resulting in low yields and poor tuber quality. The yield response of potato genotypes to water supply was investigated in six trials, three each in spring and autumn plantings. Trials were conducted under automated rain shelters, using an irrigation boom to impose five soil water regimes.The negative effect of water stress on tuber yield was more detrimental in spring than in autumn, because of higher atmospheric evaporative demand and higher temperatures in spring. An average yield reduction of 68% was recorded for the most severely stressed regime in spring plantings, while the mean reduction for the same treatment in autumn was only 42%. Genotypic differences in yield response to drought were clearly illustrated in spring, but not in autumn. This suggests that the choice of genotypes is only influenced by the availability of water in spring, when more drought tolerant genotypes should be used.

The effect of stem population on tuber yield in a trial with single-stem seed pieces

SummaryExcised eyes on 5 g of seed tuber tissue were used to grow plants with single stems. These were transplanted in the field at densities of 120 000, 180 000 and 240 000 plants/ha, with in-row spacings of 16 or 33 cm. Total tuber yield was not affected, although more tubers were produced at the high densities. Tuber numbers did not increase in proportion to the number of stems. This was due to the fact that the number of tubers per stem decreased from a mean of 4.8 to 2.9 with increasing stem populations.

Application of Farmyard Manure Improved the Chemical and Physical Properties of the Soil in a Semi-Arid Area in Ethiopia

ABSTRACT A field experiment was conducted to assess the effect of the integrated use of farmyard manure and inorganic fertilizers on soil chemical properties in a semi-arid area in NE Ethiopia. Twelve treatments comprising factorial combinations of four levels of FYM (0, 5, 10 and 15 t ha 1 annum 1) and three levels of inorganic fertilizers (0, 50 and 100% of the recommended rate) were compared in a randomized complete block design with three replications over a period of 6 years. The results revealed substantial increases in total N, available P, exchangeable K and organic carbon contents of the soil with the application of 5 to 15 t FYM ha 1. NPK content of the soil increased with the level of FYM application. The inorganic fertilizer treatments had no effect on soil fertility. The application of FYM and inorganic fertilizer did not affect exchangeable Na+, Ca2+, Mg2+, cation exchange capacity, base saturation or soil pH. Significant increases in soil N balance and soil water content were observed with FYM application. It can be concluded that with the application FYM at 5, 10 and 15 t ha 1 soil degradation under continuous cultivation can be reversed within a relatively short period of time.

The effect of plant population on the quality of sunflower seed for processing

Among other disadvantages, low hullability of sunflower seed results in oil cake with a high fibre and low protein content. Hullability is known to increase with increased seed size. Seed size generally decreases with an increase in plant density. The objective of this experiment was to determine the effect of plant density on hullability other physical trails and chemical seed composition of three sunflower cultivars. In a field trial at Potchefstroom the cultivars HV 3037, PAM 7392 and SNK 37 were planted in rows 0.9 m apart at densities of 20 000, 35 000 and 50 000 plants per ha in a randomised complete block, design with two replicates. Yield and seed trails differed among cultivars. Seed oil and protein content was not affected by plant population. Grain yield and hull content were significantly higher for the 20 000 than for the 35 000 and 50 000 populations. The thousand seed weight, a measure of seed size, decreased for all cultivars with increased plant population, The hullability of HV 3037 and SNK 37 declined with increased plant population, while it changed relatively little for PAH 7392. Higher hullability for the 20 000 population resulted in a higher protein content of the kernel rich fraction. Indications are that plant populations lower than the recommended 35 000 plants ha−1 will maximise hullability and minimise losses due to fine material.

Interaction between cultivar and soil fertility on grain yield, yield components and grain nitrogen content of wheat

The effect of soil nutrient status on the performance of four wheat cultivars was studied in a long-term field experiment at the University of Pretoria. The objective was to quantify the effect of soil nutrient status on yield, yield components and grain quality characteristics, using a split-plot design in a randomized complete block, replicated four times. Grain yield and nitrogen content differed between cultivars with SST 86 yielding 3903 kgha-1(2.47%N), Inia 4484 kgha−1(2.53%N), Kariega 4447 kgha−1(2.49%N) and Carina 6343 kgha−1(3.58%N). Increasing soil fertility increased grain yield, grain number, spikelet number, grains per spike, grains per spikelet, grain nitrogen, biomass and harvest index, but depressed kernel mass. Significant interactions between cultivar and soil fertility were observed for grain yield, grain number, biomass, harvest index and kernel mass. It is concluded that wheat cultivars differ in their potential to utilize limited soil nutrients to produce yield and quality.

pH of the Pod-zone Affects Reproductive Growth of Groundnut

ABSTRACT Most of the sandy soils that are suitable for production of groundnut (Arachis hypogaea L.) in the tropic and subtropics are acidic. Whilst effects of pH in the root zone have been studied, the effects of pod-zone pH on groundnut productivity remain relatively unknown. To develop appropriate soil management practices for groundnut production on acid soils, it is essential to understand how low pH affects reproductive growth of groundnut. Consequently, a glasshouse experiment was conducted in which attached groundnut gynophores were cultured in solution at pH ranging from 3.0 to 7.0. Low pH delayed pod initiation, and resulted in almost no pod expansion at pH 3.0. Only 12% and 55% of the cultured gynophores developed into pods at pH 3.0 and 4.0, respectively, compared with 91–95% at pH ≥ 5.0. Pods produced at pH 3.0 contained no seeds and those produced at pH 4.0 had a hollow, dark colored area in the cotyledon. Normal seeds and embryos were formed at pH ≥ 5.0, and plumule development was faster at solution pH ≥ 5.0 than at pH 4.0. Pod and kernel dry mass were optimised (90% of maximum) at pH 5.62–6.69 and 5.65–6.78, respectively. Septate and non-septate pod hairs were formed at all solution pH regimes, but were denser and more persistent at the higher pH. Kernel calcium (Ca) concentration decreased with decreasing pH, and was highly correlated with solution pH. Thus, pod-zone pH has important effects on the reproductive growth of groundnut, emphasizing the importance of managing pod-zone pH.