The growth of plants is controlled by the availability of photosynthesized carbohydrates. Since both rainfall and sunshine are needed for photosynthesis an empirical expression is proposed which relates vegetative growth to the product of rainfall and bright sunshine hours over a specified period. Tea is a crop in which the yield is entirely vegetative and harvested throughout the year. Laycock's data for tea yields from constant treatment plots in Malawi show that yield was strongly correlated with the product of rainfall per month (R) and average daily hours of sunshine per month (S) for the previous month (r=0·972). The graph of yield vs RS for the previous month gives a straight line passing through the origin. This empirical weather parameter RS appears suitable for the study of vegetative harvests.

Uptake of the major nutrients by maize was determined throughout the growing season. Little phosphorus was accumulated, as reflected in its distribution within the plants, but uptake of labelled phosphorus showed two distinct peaks associated with root development. One fifth of the applied phosphorus was recovered by the plants.

An experiment on wheat (variety Mexipak) was undertaken for two years at the Experimental Farm to study the effects of soil and foliar application of urea. The results indicated appreciable increases in grain yields due to foliar sprays of urea during both years of the experiment; the spray helped to increase yield-contributing factors such as thousand-grain weight, weight of grains per plant, plant height and dry weight.

Four fertilizer placement methods (ring, sideband, broadcast and furrow) applied ten weeks after planting were compared in nine experiments to determine the best method for fertiliza- tion of white yam (Dioscorea rotundata). Significant yield differences due to the treatments were observed at Mbato, Umudike and Igbariam in 1980 and at Nsukka and Igbariam in 1981. Best yields overall were obtained with the sideband method, followed by broadcast, ring and furrow in that order. However, man-days taken to fertilize one hectare by ring, sideband, furrow and broadcast methods were 11.2, 10.9, 2.8 and 1.5, respectively, so that in this regard, broadcast is preferable to the other placement methods.

Changes in seed viability over 12 months of low-input storage conditions were monitored on five diverse seed species grown in the tropics: amaranth (Amaranthus cruentus), lablab bean (Lablab purpureus), moringa (Moringa oleifera), pumpkin (Cucurbita moschata) and tomato (Solanum lycopersicum). Because the costs of maintaining low-temperature storage can be prohibitively expensive in developing countries, this study explored alternatives to low-temperature storage at the Educational Concerns for Hunger Organization (ECHO) Asia Impact Center Seed Bank in Northern Thailand. Specifically, this research compared the effects of vacuum sealing and refrigeration on stored seed viability in both laboratory and field settings. While seed species was an influential factor in determining seed longevity, the relative importance of vacuum sealing and refrigeration differed for the dependent variables of seed moisture content, germination rate, mean time to 50% germination and field emergence. Although the combination of vacuum sealing and refrigeration was most effective at conserving seed quality as measured by each of these variables, the storage of seeds in vacuum-sealed packages at ambient temperatures was more effective than unsealed but refrigerated packets at conserving low moisture content and high germination and field emergence rates across species. This suggests that for resource-constrained seed banks in the tropics, vacuum sealing with or without refrigeration may represent a viable alternative to other expensive and energy-intensive storage techniques.

The adaptation of extra-short-duration (ESD) and short-duration (SD) pigeonpea (Cajanus cajan) genotypes to the short rainy season (late March to late May; yala) was studied in Sri Lanka in 1995 and 1996. Eight ESD and two SD genotypes were sown on two dates in April and May, with and without supplementary irrigation. In addition, pigeonpea ESD genotype ICPL 88039, and SD genotype ICPL 86012, sesame (Sesamum indicum cv. M.I.3), blackgram (Vigna mungo cv. M.I.1) were compared under rainfed zero-tillage conditions after a rice crop at two locations in 1996. Grain yields of the pigeonpea genotypes under rainfed conditions ranged from 0.07 to 0.47 t ha−1 in the early sowings and 0.09 to 0.42 t ha−1 in the late sowings. The irrigated yields reached 1.7 t ha−1 in early sowing and 1.3 t ha−1 in the late sowings. Irrigation differentially influenced the performance of pigeonpea genotypes in both the sowings in 1996. Analysis of pooled data showed highly significant genotype × environment (year–sowing–irrigation combination) interactions. The interaction pattern among genotypes was associated with differences in the length of the reproductive period and the partitioning coefficient of genotypes. ICPL 88039, with the shortest reproductive period and one of the best in partitioning efficiency, recorded maximum mean yield. As a rainfed post-rice crop in farmers’ fields, ICPL 88039 yielded 0.43–1.4 t ha−1 which exceeded yields of SD pigeonpea (0.02–0.88 t ha−1), blackgram (0.03–1.00 t ha−1) and sesame (0–0.09 t ha−1). The results suggest scope for introducing ESD genotypes as a sole crop in the yala season in Sri Lanka since genotypes with short reproductive periods and high partitioning efficiencies are likely to have better adaptation to this season.

Pollen of the oil palm (Elaeis guineensis) was vacuum dried for various lengths of time and stored under vacuum in ampoules at 28°, 5° and −10°C. Little loss in viability over a period of 12 months was observed in any of the storage treatments when vacuum drying did not exceed one hour. Progenies resulting from crosses with pollen stored three months under vacuum have shown no anamolous seedling development.

Evaluation of the yield stability of a group of CIMMYT tropical maize populations across international environments, measured by the performance of varieties derived from them, showed that the populations Mezcla Tropical Blanca, La Posta and Amarillo Dentado produced the most stable varieties across environments. Mezcla Tropical Blanco and Amarillo Dentado produced selections with good stability in both low and high yielding environments while La Posta produced varieties with better performance in favourable environments. ‘Across-site’ varieties were not consistently more effective than ‘site-specific’ varieties in improving yield stability. Varieties selected for some specific population-environment combinations have been very stable in other areas of the world.

In the preceding paper in this series (Pearce, 1992) it was explained how an experimenter can ask specific questions about the treatment responses and can obtain answers to them by using contrasts of interest. Here, two standard cases are examined, one in which treatments are quantitative in nature, like the amount of fertilizer applied or the dates on which spraying takes place, and the other in which the treatment set is formed from all combinations of two or more other sets. (Such a ‘factorial set’ might be formed from several kinds of herbicide being used with a range of cultivations.) Finally, a non-standard example is examined in which a well considered set of treatments provided information directly relevant to the subject of enquiry. The subject is considered with some emphasis on testing, but in many instances estimation would be better.

Two years study was made on variability in 42 indigenous and exotic varieties of sesame. With very few exceptions, highly significant differences were found between the varieties for the 15 characters investigated. A wide range of phenotypic and genotypic variability was exhibited by all characters except oil, protein and moisture, and 9 out of 15 characters gave heritability estimates exceeding 80 per cent. To relate heritability values to other genetic parameters, a ‘rank procedure’ showed that the characters followed one another in a definite order.

In this study, the CERES-Maize model was calibrated and evaluated using data from 60 farmers’ fields across Sudan (SS) and Northern Guinea (NGS) Savannas of Nigeria in 2016 and 2017 rainy seasons. The trials consisted of 10 maize varieties sown at three different sowing densities (2.6, 5.3, and 6.6 plants m−2) across farmers’ field with contrasting agronomic and nutrient management histories. Model predictions in both years and locations were close to observed data for both calibration and evaluation exercises as evidenced by low normalized root mean square error (RMSE) (≤15%), high modified d-index (> 0.6), and high model efficiency (>0.45) values for the phenology, growth, and yield data across all varieties and agro-ecologies. In both years and locations and for both calibration and evaluation exercises, very good agreements were found between observed and model-simulated grain yields, number of days to physiological maturity, above-ground biomass, and harvest index. Two separate scenario analyses were conducted using the long-term (26 years) weather records for Bunkure (representing the SS) and Zaria (representing the NGS). The early and extra-early varieties were used in the SS while the intermediate and late varieties were used in the NGS. The result of the scenario analyses showed that early and extra-early varieties grown in the SS responds to increased sowing density up to 8.8 plants m−2 when the recommended rate of N fertilizers (90 kg N ha−1) was applied. In the NGS, yield responses were observed up to a density of 6.6 plants m−2 with the application of 120 kg N ha−1 for the intermediate and late varieties. The highest mean monetary returns to land (US$1336.1 ha−1) were simulated for scenarios with 8.8 plants m−2 and 90 kg N ha−1, while the highest return to labor (US$957.7 ha−1) was simulated for scenarios with 6.6 plants m−2 and 90 Kg N ha−1 in the SS. In the NGS, monetary return per hectare was highest with a planting density of 6.6 plants m−2 with the application of 120 kg N, while the return to labor was highest for sowing density of 5.3 plants m−2 at the same N fertilizer application rates. The results of the long-term simulations predicted increases in yield and economic returns to land and labor by increasing sowing densities in the maize belts of Nigeria without applying N fertilizers above the recommended rates.

Wheat grown under zero tillage (ZT) and raised-bed following a legume crop may have a variable N requirement compared with conventionally-tilled flat-sown crop. A field experiment was conducted for two years during 2005–07 to study the effect of varying tillage (conventional and zero), crop establishment (flat and raised-bed sowing) and N fertilization (0–160 kg N ha−1) on wheat grown after greengram at New Delhi, India. Rainy-season greengram performed equally well under flat and raised-bed planting, but the seed yield was 25.9% lower under ZT than conventional tillage (CT) conditions. Wheat following greengram during winter season also showed better growth and yield under CT than ZT, as well as under flat sowing than furrow-irrigated raised-bed (FIRB) system. The grain yield was highest under CT-flat, and decreased by 5.4–9.4% under FIRB system. Nitrogen fertilization up to 120 kg N ha−1 under CT and 160 kg N ha−1 under ZT increased grain yield, and the optimum doses were worked out to be 147.1 and 154.2 kg ha−1, respectively. Nitrogen-use efficiency decreased with N levels but remained more or less similar under tillage and crop establishment practices. Maximum returns and B:C ratio were obtained under CT-flat, followed closely by ZT-flat.

Data recently published in this journal on grain yields of new rice varieties, grown under rainfed conditions on-farm in two villages in Uttar Pradesh, were analysed. The new varieties were spectacularly better than the landraces with which they were compared and showed a high regression slope (>2) against the landraces. If supported by further studies, such experiments could provide an appropriate, but hitherto unexplored, approach to plant breeding for poor, small farmers operating with low inputs.

A study was conducted, including 17 oil palm (Elaeis guineensis Jacq) crops distributed throughout Colombia, to determine how much silicon (Si) this plant species accumulates in their leaves, and also to determine the available Si levels in the soils. The study was conceived as a preliminary step of a research project aimed at determining whether the beneficial effects of Si, which have been identified for other species also, occur in the oil palm crop. Available Si varied among soils; lower levels were found in the soils with characteristics associated with greater weathering as compared with less weathered soils. Relatively high leaf Si levels were found in all of the sites studied and this was interpreted as an indication that oil palm could be considered a Si accumulator. An increase in Si concentration with leaf age was found, indicating that this element probably behaves as a non-mobile element in the plant. A defined relationship between soil available Si and Si concentration in the leaves was not found, however. The results indicate that it is worthwhile conducting specific studies to determine the effects of Si on oil palm growth and behaviour, and provide useful criteria for the design of future studies.

Yields of maize were determined in six years, on two soils, at up to four nitrogen levels following early and late planting. Without fertilizer nitrogen, high rainfall at the beginning of the growing season reduced yield on one soil but not on the other, while high rainfall at late silking and high total rainfall in the growing season reduced yields on both soils. As the level of fertilizer nitrogen increased, the negative effects of rainfall on yield tended to disappear. A three week delay in planting sometimes increased and sometimes decreased yield. The probable reasons for the observed effects of rainfall on yield are discussed.

Effects of defoliating jackbean for forage production and time of sowing were studied in field experiments as part of an evaluation of the potential of jackbean and in order to determine appropriate cultural practices for the crop. In a long growing season, seed yield after cutting for forage was similar to that of an uncut crop but was reduced by two thirds in a short growing season. Flowering appeared to be stimulated in short days. Delayed sowing after the beginning of the rainy season progressively reduced seed yields

The climates to which lentil (Lens culinaris) crops are exposed can vary appreciably depending on location and date of sowing. The effects on growth, development and seed yield when three USA cultivars experienced relatively warmer or cooler day/night temperatures during the vegetative period were investigated in growth cabinets. Plants were nodulated and supplied with either 20 or 80 ppm inorganic N; they differed appreciably in morphology and vegetative vigour, and so in their potential for subsequent pod production, depending on pre-flowering temperature and on nitrogen nutrition. Variations in seed yield were largely a consequence of treatment and cultivar effects on pod number per plant, and a pre-flowering temperature regime of 21°/7°C (mean 14.9°C) was supra-optimal. The pre-flowering environment clearly affects potential pod production and has persistent effects on the capability of plants to fill the pods produced.

In 90 local sesame types there was some association between seed coat colour and seed size, stem height, number of branches, number of pods, yield per plant and earliness. Forty-five coefficients show the degree of correlation between ten agronomic characters. Yield was significantly and positively correlated with all characters except the number of days to first flowering and to first maturity. Stem height, number of pods per plant and seed size seem to be the best criteria for selection in sesame.

Maize (Zea mays L.) is the most important staple crop in West and Central Africa (WCA), but its production is severely constrained by low soil nitrogen (low N). Fifty-six extra-early open-pollinated maize cultivars developed during three breeding eras, 1995–2000, 2001–2006 and 2007–2012, were evaluated under low N and high soil nitrogen (high N) at two locations in Nigeria in 2013 and 2014, to investigate the genetic gains in grain yield and identify outstanding cultivars. During the first breeding era, the emphasis of the programme was on breeding for resistance to the maize streak virus (MSV) and high yield potential, while the major breeding emphasis during the second era was on recurrent selection for improved grain yield and Striga resistance in two extra-early-maturing source populations, TZEE-W Pop STR (white) and TZEE-Y Pop STR (yellow). Starting from the third era, the source populations were subjected to improvement for tolerance to drought, low N and resistance to Striga. A randomized incomplete block design with two replications was used for the field evaluations. Results revealed genetic gains in grain yield of 0.314 Mg ha−1 (13.29%) and 0.493 Mg ha−1 (16.84%) per era under low N and high N, respectively. The annual genetic gains in grain yield was 0.054 Mg ha–1 (2.14%) under low N and 0.081 Mg ha–1 (2.56%) under high N environments. The cultivar 2009 TZEE-OR2 STR of era 3 was the most stable, with competitive yield across environments, while 2004 TZEE-W Pop STR C4 from era 2, and TZEE-W STR 104, TZEE-W STR 108 and 2012 TZEE-W DT STR C5 from era 3 were high yielding but less stable. These cultivars should be further tested on-farm and commercialized in WCA. Substantial progress has been made in breeding for high grain yield and low-N tolerance in the sub-region.

This research aimed to develop a typology of agriculture in Timor-Leste using national census data at the village level. Although Timor-Leste is a relatively small nation, its varied topography contains a rich diversity in agricultural livelihoods, from coffee covered mountains, to dryland-swidden agriculture. Each of the livelihoods are very complex, with a single household often managing more than 10 crop and 4–5 animal species in very small holdings. Using census data from each village only, statistical clustering analysis was used to group villages with similar levels of participation in crop and livestock production. The clustered village groups were then mapped, and it was seen that villages in each cluster, occupied particular locations. Using expert knowledge about the locations of each cluster, livelihood zones based on a small number of rules were defined to mimic the output of the clustering. Seven livelihood zones were identified from mapping the livelihood systems. These included three zones with irrigation (rice-based), two highland zones (coffee-based) and two lowland zones based on rain-fed agriculture. Government and development agencies have endorsed the typology of livelihood zones, which is now in use for planning and decision-making. The technique of using national census data to define agricultural zones through statistical clustering can be replicated wherever there is reliable village-level census data.