Seed dormancy was found in the Mexican sesame cultivar Cola de Borrego but it disappeared about 6 months after harvest. Dormancy was completely broken by soaking the seeds in GA3 solutions of 100 and 500 ppm for 48 h; soaking in 1000 ppm GA3 concentration was helpful but not as good as the 100 and 500 ppm treatments. GA3 treatments also hastened emergence.

Data from 110 on-farm vegetable trials conducted in Jamaica were examined to seek guidelines as to how on-farm trials should be executed in order to obtain quality data. The results show that while one-way blocking is useful in designing experiments it may sometimes be inefficient and that two-way blocking is generally preferable. If only a small number of trials can be conducted then it is important that up to four or five replications of each treatment are used at each site. Plot sizes should be larger than those used for on-station trials. Due to low correlations between results from different sites, experiments should be conducted at many sites. Thus a large number of trials should be planned to allow for treatment–environment interactions and trial failures.

Although the relationship between the length of a growing tea shoot and time is not truly exponential, the exponential relative shoot extension rate (ERSER) can be used for comparisons when both the initial shoot lengths and the periods of measurement are identical. An empirical method to adjust ERSER for variations in initial shoot length was developed for weekly field measurements of seven tea clones in Malawi. ERSERs, measured throughout the two growing seasons after the bushes had been pruned, were standardized to an initial shoot length of 2.5 cm and were then related to mean weekly air temperatures and to vapour pressure deficits. There were large clonal differences in the response of ERSER to temperature within the range 18–23°C. Shoots of the vigorous Malawi clone SFS 150 elongated rapidly at all temperatures, but notably at the lower temperatures (18–20°C). Two Kenyan clones, BB/35 and K6/8, did not grow well at about 18°C, which is normal for growth in Kenya but which coincides with the period of short daylengths (less than 12 h) in Malawi. A significant decrease in ERSER was found with increased vapour pressure deficit over the whole range of field measurements and ERSERs were uniformly lower in the second year after pruning. The results suggest that the usual calculations to derive an inherent base temperature for elongation are not valid unless elongation is truly exponential and therefore, in general, base temperatures should not be used for comparisons between experiments.

A two-year study was undertaken in a tropical dryland agro-ecosystem to evaluate the effect of the application of soil amendments with contrasting chemical natures on crop productivity, grain yield, N-uptake and N-use efficiencies. The treatments involved the addition of equivalent amounts of N (80 kg N ha−1) through chemical fertilizer and three organic inputs at the beginning of the annual cycle: Sesbania aculeata shoots (high quality, C/N 16), wheat straw (low quality, C/N 82) and Sesbania+wheat straw (high and low quality combined, C/N 47), together with a control treatment. Test crops consisted of an annual sequence of rice and barley, sown in the rainy and winter seasons, respectively. Fertilizer and Sesbania inputs resulted in higher total net productivity (TNP) for the rice crop (47 % and 32 % increases over the control, respectively) than the combined (+28 %) and wheat straw treatments (+10 %). During the succeeding barley crop, maximum TNP was recorded in the Sesbania+wheat straw treatment (+52 %), followed by wheat straw (+43 %), fertilizer (+19 %) and Sesbania (+17 %). The TNP and grain yields of both crops added together were higher in Sesbania+wheat straw and fertilizer treatments compared to a single applications of either Sesbania or wheat straw. The Sesbania+wheat straw and fertilizer treatments resulted in more efficient utilization of N compared to the other treatments. Crop roots played a pivotal role in N-recovery from the soil and their N concentrations differed significantly (p < 0.05) due to the application of soil amendments. Across different treatments, crop root biomass was strongly correlated with crop N-uptake (r = 0.81, n = 10, p < 0.05), recovery efficiency (r = 0.81, n = 8, p < 0.05) and agronomic efficiency (r = 0.81, n = 8, p < 0.05). It is suggested that the combined application of high and low quality resources modulated N release, resulting in relatively higher productivity through the annual cropping cycle. Such combined inputs may prove useful in developing low input, environment friendly soil management practices in tropical dryland agro-ecosystems.

The response of groundnut plants to CCC was investigated by applying concentrations of 0, 500, 1000 and 1500 ppm three times as a foliar spray. CCC at 500 ppm gave more kernels, and heavier yields of pods, kernels and oil, than 1000 or 1500 ppm or the control treatment. Application of CCC resulted in a greater percentage of shell and of moisture in the whole pod than in the control.

The relation between some growth parameters in polybag oil palm nursery seedlings were assessed. ‘Non-destructive’ parameters such as leaf number, seedling height and girth were highly and positively correlated with one another and with the dry weight of seedlings. Amongst the ‘destructive’ parameters only leaf area, height/weight ratio and fresh weight were positively correlated with dry weight. The Leaf Area Index was poorly correlated with other parameters examined. The relevance of these findings to the selection of oil palm seedlings for transplanting into the field is discussed.

Experiments in bulbil nurseries and field sisal were carried out in N.E. Tanganyika, 5°S, 39°E, 200 m. above sea level, at a mean annual rainfall of 1160 mm., on deep red loam. The discussion covers the establishment of sisal through a polythene mulch, the control of weed growth, the persistence of polythene of different thicknesses and from different sources, and some effects on growth of the sisal and on soil properties. A mulch of black polythene improved the growth of bulbil nurseries by 30 per cent or more, due to conservation of soil moisture and elimination of weed competition and disturbance associated with the removal of weeds by hoeing. For nurseries 150-gauge material was preferred, but there were important differences in the persistence of material purchased from two sources. Where black polythene is used in a nursery the density can be increased from 80,000 to 110,000 plants per hectare, to help offset the high cost of the material. A mulch of 250-g. black polythene controlled weeds in field sisal but did not improve growth.

The North China Plain is an important summer maize/winter wheat rotation area. However, over the years, continued intensive tillage has destroyed the soil aggregate accelerating the mineralization and decomposition of soil organic carbon (SOC), which plays an important role in soil quality, as increased organic carbon storage improves soil fertility and crop yields. Thus, the objective of this study was to explore the comprehensive impact of tillage methods on soil aggregates, aggregate-associated SOC, and carbon sequestration capacity under a regime of straw return. In 2002, we started a 14-year long-term tillage experiment; then in 2016–2017, we tested the following tillage methods, zero tillage (ZT), rotary tillage (RT), subsoiling (SS), and conventional tillage (CT). The results showed that in the 0–10 cm soil layer, tillage methods significantly reduced the proportion of aggregates in the order of 2–0.25 > 5–2 > 0.25–0.053 mm. Additionally, conservation tillage (i.e., SS and ZT) significantly increased the percentage of macroaggregates (0–40 cm) and their SOC content, compared to CT. Additionally, the contribution rate of macroaggregates to SOC was 17.2% and 30.6% higher under SS and ZT than under CT, respectively. Conservation tillage methods improved the carbon sequestration capacity of soil aggregates. Our study provides a theoretical basis for the development of more suitable tillage methods. Furthermore, long-term conservation tillage seemingly protected large aggregates and, SOC, whereby carbon sequestration was enhanced and soil carbon emissions were effectively reduced.

Field studies designed to investigate the effects of sett size and spacing on tuber yield of white Guinea yam were conducted in three locations over a two year period in the rainforest and savanna zones of Nigeria. Sett weights larger than 400 g could be used for maximum tuber yields in both forest and savanna zones. Spacing had no significant effects on tuber yield in the savanna zone, but optimum spacing has yet to be identified in the forest zone.

Experiments were conducted during the winter seasons of 1992–93 and 1993–94 at the Lumle Agricultural Research Centre and its off-station research site at Lopre in Nepal to study the agronomic performance and profitability of barley (Hordeum vulgare) and peas (Pisum sativum) mixed intercropping (that is, without any row arrangement) in the subsistence farming systems of the Nepalese hills. Sole crops of barley (cv. Bonus and Local) at 100kg seed ha−1 were compared with a pure stand of peas (cv. Tikot Local) sown at 60kg seed ha−1 and with peas intercropped with both varieties of barley at 100:40 or 100:20 kg seed ha−1. Results across two locations for two seasons showed that the barley+peas intercropping was advantageous in terms of overall grain yield, land equivalent ratio (LER), monetary advantage, economic return and dietary provision in the subsistence farming system. It also provided yield stability under adverse climatic conditions. Barley genotypes differed in their suitability for intercropping with peas. The yield of Local barley was reduced when peas were intercropped with it at both seed rates but this was not so with Bonus. The most appropriate combinations to realize the maximum advantage from intercropping were Bonus barley+peas at 100:20 kg seed ha−1 and Local barley+peas at 100:40 kg seeds ha−1. A combination of Bonus barley and peas at 100:20 kg seed ha−1 enabled farmers to harvest an additional 400 kg grains ha−1 from peas without significantly reducing the grain yield of barley. The study also verified through formal experimentation that the traditional practice of mixing barley and peas is advantageous.

Spatial nutrient distribution was studied under a three-and-a-half-year-old fallow of Dactyladenia barteri, Alchornea cordifolia, Senna siamea and Gmelina arborea hedgerows grown on an acid Ultisol in southeastern Nigeria. The objectives were to evaluate the nutrient cycling capacity and suitability of the hedgerow species for alley cropping. No consistent patterns were observed in the lateral distribution of soil pH, total nitrogen, organic carbon, available phosphorus, exchangeable cations (potassium, calcium, magnesium and sodium), total acidity and effective cation exchange capacity in the 4 m wide alleys formed between the hedgerow species. Senna siamea and Gmelina arborea tended to increase soil organic carbon, calcium, magnesium and effective cation exchange capacity, particularly in the top 50 cm, compared with Alchornea cordifolia and Dactyladenia barteri, and can therefore be recommended for soil fertility regeneration on acid Ultisols during periods of fallow. However, they appear to be less suitable for alley cropping than Dactyladenia barteri because they are shallow rooting.

Propiedades químicas delo suelo bajo cuatro especies de seto vivo

Yield response to a range of plant densities (0·7–7·2 plants m.−2) achieved by uprooting plants at random was curvilinear, with an optimum plant density of 3·3 plants m.−2 at which fertilizer increased the yield at Makoka by over 1000 kg. ha.−1 to 2227 kg. ha.−1. There was no interaction between fertilizer and plant density. At Ngabu there was no response to fertilizer. Top dressing was effective on unfertilized cotton at Makoka, but filling in was ineffective at both sites. A method of partitioning components of yield is described which illustrates the stages of plant development which benefitted or were adversely affected by the different agronomic practices.

Azolla and blue-green algae (BGA) inoculated in a rice field produced a higher biomass and fixed more nitrogen in transplanted than in direct-seeded rice. Application of Azolla, BGA, composts of Eichhomia and Azolla and green manuring with Sesbania increased tiller numbers, height, grain and straw yields, and nitrogen uptake by rice in both the transplanted and the direct-seeded crop. The growing and incorporating of three Azolla crops with the rice crop produced more grain than the use of other nitrogen sources but the rice crops showed a poor response to inoculation with BGA. The yield of rice following green manuring with Sesbania or the use of two crops of Azolla after transplanting was similar to that of a crop receiving 60 kg N ha−1 as urea, but smaller yields resulted from the use of composts of Azolla and Eichhornia.

Bush area, shoot number and yield were all strongly and positively correlated in 100 young seedling tea bushes. Clones derived from the bushes exhibited characteristics which were correlated with those of the mother bushes, indicating the usefulness of these observations in the selection of clones for improved performance.

Two field experiments on the effects of watering at 40–50 (M1), 60–70 (M2), 80–90 (M3) and 90–100% (M4) of available soil-moisture depletion on sugarcane were conducted at Guneid during 1974–77. Intensive cane growth was observed from April to August. Irrigation treatments significantly affected yields of cane and sugar, and the percentage of sucrose, with treatment M2 giving the most economic yields of cane and sugar.

A field experiment was conducted for two consecutive years commencing in 1979–80 on the Indo-Gangetic alluvial soil of Pura to investigate the requirements for zinc of wheat, chickpea, mustard and Egyptian clover. Chickpea and Egyptian clover were more sensitive to zinc deficiency than wheat and mustard, respectively. Average total dry matter production by Egyptian clover and wheat was larger than mustard and chickpea. Egyptian clover and wheat required more zinc to achieve maximum dry matter production but they also recovered from the soil a larger proportion of applied zinc than chickpea and mustard. Mustard produced the most dry matter per unit of zinc absorbed.

Impact assessment hinges on reliable indicators of technology uptake, but this poses particular challenges for new agronomic practices in emerging economies. This paper presents a triangulation approach to assess technology diffusion and illustrates it by assessing the extent and dynamics of zero tillage wheat in South Asia's rice-wheat systems. Various diffusion indicators from three different data methods (secondary data, supply-side surveys, demand-side surveys) are contrasted for two different locations (India's Haryana State and Pakistan's Punjab province) for the period 2000–2004. Such multi-indicator, multi-site and multi-year triangulation enhances the robustness of the inferences and provides the necessary perspective. The three sources coincide in terms of diffusion of zero tillage wheat having increased since 2000, but in particular the empirical surveys show a much slower uptake and subsequent stagnation in the Pakistan Punjab study area. The paper thereby reiterates the need for empirical ground truthing of technology uptake and the need for robust and complementary diffusion indicators.