The macadamia nut is the only commercial food crop indigenous to Australia. It originated along the fringes of rainforests, only becoming an important internationally traded crop in the late 20th century. Australia is now the main centre of production, following a lead set by Hawai'i. The crop is also important in Central America and southern Africa. The majority of recent research reported in the literature on the physiology and water relations of macadamia has been undertaken in Australia. Macadamia is a tall evergreen tree in which vegetative growth occurs in a series of flushes. Mild water stress suppresses growth, but compensatory growth occurs on re-watering. Flowers form on hardened wood within the leaf canopy. Floral initiation occurs in late autumn, with flowering in the following spring. Flowering is profuse but only 5–10% of the flowers set fruit and less than 1% of the flowers reach maturity as fruits due largely to premature abscission. High temperatures (>30 °C) can contribute to the shedding of fruit. It takes about 12 months from floral initiation to the completion of harvest. Macadamia root systems are described as relatively shallow and spreading. The taproot can extend to depths of >1.2 m, with a dense matt of fibrous roots in the top 0.4 m. Proteoid rootlets are also present. Stomata are only found on the abaxial surface of the leaf. Macadamia has several attributes that help to explain its apparent tolerance to periodic dry conditions as found in its native habitat. These include leaves with xeromorphic adaptations, stomatal closure without concurrent changes in leaf water potential and an efficient water transport system. There has only been one serious attempt to measure the actual water use of macadamia. Most irrigation experiments have been poorly planned and/or the outcomes were inconclusive. Nut yields are cyclical and highly variable, making it difficult to establish cause and effect. It is not yet possible to say with evidence where and when irrigation is worthwhile.

The arid zone of northwestern India is a unique adaptation zone for crop plants because of its pervasive severe moisture stress and high temperatures. Pearl millet (Pennisetum glaucum) is a major cereal in this zone as it represents approximately 25% of the total acreage of the crop in the country. Pearl millet hybrid cultivars, which have gained widespread acceptance from farmers elsewhere in the country, have not been adopted in the arid zone. Farmers continue to sow their traditional landraces because the yield advantage of current hybrids is not expressed in this zone, and the risk of failure in poor years with the hybrids is unacceptably high. The International Crops Research Institute for the Semi-Arid Tropics and the Indian Council of Agricultural Research have been collaborating to understand the unique nature of pearl millet in the arid zone since the late 1980s. This collaboration has produced a better understanding of how arid zone farmers manage their germplasm, of the unique features of this invaluable resource and of a range of ways of using this germplasm to produce well-adapted new varieties and hybrids that will meet the requirements of the farmers of the arid zone. It has been shown that new cultivars for the arid zone need to be based on parental materials, including traditional landraces that are specifically adapted to the arid zone. This paper summarizes the main lessons of nearly 20 years of this collaborative research.

Field experiments were conducted to standardize protocols for site-specific fertilizer nitrogen (N) management in Bt cotton using Soil Plant Analysis Development (SPAD) chlorophyll meter. Performance of different SPAD-based site-specific N management scenarios was evaluated vis-à-vis blanket fertilizer N recommendation. The N treatments comprised a no-N (control), four fixed-time and fixed N doses (60, 90, 120, and 150 kg N ha-1) including the recommended dose (150 kg ha-1), and eight fixed-time and adjustable N doses based on critical SPAD readings of 45 and 41 at first flowering and boll formation stages, respectively. The results revealed that by applying 45 or 60 kg N ha-1 at thinning stage of the crop and critical SPAD value-guided dose of 45 or 30 kg N ha-1 at first flowering stage resulted in yields similar to that recorded by applying the recommended dose of 150 kg N ha-1. However, significantly higher N use efficiency as well as 30–40% less total fertilizer N use was recorded with site-specific N management. Applying 30 kg N ha-1 at thinning and SPAD meter-guided 45 kg N ha-1 at first flowering were not enough and required additional SPAD meter-guided 45 kg N ha-1 at boll formation for sustaining yield levels equivalent to those observed by following blanket recommendation but resulted in 20% less fertilizer N application. Our data revealed that SPAD meter-based site-specific N management in Bt cotton results in optimum yield with dynamic adjustment of fertilizer N doses at first flowering and boll formation stages. The total amount of N fertilizer following site-specific management strategies was substantially less than the blanket recommendation of 150 kg N ha-1, but the extent may vary in different fields.

In monsoon climates, the mean daytime saturation vapour pressure deficit (D), measured at screen height, decreases from a maximum of 3–4 kPa attained several months before rain arrives to a minimum of 0.5–1 kPa in the month of highest rainfall. Climatic records from India and West Africa were analysed to give the relation between D and precipitation (P mm month−1) as:

where n ranged from 0.5 to 0.9 between stations.

The dependence of dry matter production on D and therefore on P is evaluated when growth is restricted by rain and when this restriction is removed by irrigation. In the first case, the decrease in demand for water associated with a decrease in D is comparable in importance with the increase of water supply (P). The analysis has implications for the marginal response of crops to supplemental irrigation and for the interpretation of experiments with a line-source or rain-shelter.

A survey of the system of rice intensification (SRI)-related literature indicates that different authors have drawn conflicting inferences about rice yield performances under the SRI, chiefly because the SRI methodology has been variously advocated, interpreted and implemented in the field using different rice varieties, seedling ages at transplantation, cultivation seasons and nutrient management regimes. In particular, the SRI method of single-seedling transplantation (SST) has potential economic advantage due to reduced seed costs, but it is not clear whether SST is an effective management strategy across a range of seedling ages, and whether there is any specific seedling age that is optimal for yield improvement of a given rice variety. This is an important consideration in rain-fed ecosystems where variable rainfall patterns and lack of controlled irrigation make it difficult to reliably transplant at a specific seedling age as recommended for the SRI. We conducted a five year-long experiment on a rain-fed organic farm using a short-duration upland and a medium-duration lowland landrace, following the SRI methodology. Rice seedlings of different ages (6, 10, 14, 18 and 28 days after establishment) were transplanted at 25 cm × 25 cm spacing in three replicated plots. The performance for each landrace was examined with respect to productive tillers, panicle density, total grain counts per hill and grain yield per unit area. Performances of seedlings of different ages were compared with that of control plots that employed all SRI practices with the exception that 28-day-old seedlings were transplanted with three seedlings per hill. The results indicate that (1) the SRI can improve mean panicle density if seedling age ≤ 18 days, but that responses differ between varieties; (2) the number of productive tillers per hill is significantly less in SST than that of multiple seedling transplants (MST) of 28-day-old seedlings of both upland and lowland varieties; (3) the total grain numbers per hill of the lowland variety is significantly greater for 14-day-old SST than 28-day-old MST; (4) the grain yield per unit area from young SRI transplants is significantly greater than that from 28-day-old MST for the lowland variety, although the magnitude of the improvement was small; (5) for the upland variety, grain yields declined with the oldest seedlings, but planting multiple seedlings per hill made the yield of the oldest transplants on par with that of younger seedlings planted singly. Our findings suggest that transplanting younger seedlings under the SRI management may not necessarily enhance grain yields.

Minimal competition was observed between adjacent plots of climbing bean varieties and maize in association, but there was a large head border effect which was not uniform among varieties. Head borders of 1 m at each end of the plot are recommended and a net plot size of 11 m2 with 3 replications for climbing bean varieties associated with maize was found to be adequate to detect significant differences in yield of beans of 24% of the mean. For climbing beans in monoculture a somewhat smaller plot (8 m2) would achieve the same level of precision. Larger plot sizes in general were needed for maize comparisons, especially in association.

Complete nutrient ± boron treatments were imposed on seedling and young oil palms growing in sand and water culture. A number of symptoms were observed on the boron-deficient palms, including the development of high endogenous auxin levels. The relation of morphological symptoms with IAA concentration is discussed. Comparisons were made of dry matter production, leaf area and leaf boron concentration.

The profitabilities of three land use systems in the humid zone of southwest Nigeria are compared using a capital budgeting procedure combining on-station and on-farm experimental data. The systems are: non-alley farming with fallow; alley farming with fallow; and continuous alley farming. The results indicate that: continuous alley cropping is more profitable than non-alley or alley cropping with fallow; short fallowing in alley cropping reduces the rate of mining soil fertility and thus helps preserve future productivity; alley farming with small ruminants enhances the profitability of alley systems and increases their advantage over the non-alley system; and alley systems remain profitable even when terminal clearing costs are internalized in the current project cycle.

Phosphorus (P) is one of the main limiting nutrients in the semi-arid regions where pearl millet is grown; its deficiency leads to poor seedling establishment and eventually poor crop yield. Experiments were carried out in pots and field-like conditions to evaluate the effect of seed priming and seed coating with P on the shoot biomass at two and four weeks after sowing (WAS), and on the panicle and stover yield at maturity of three hybrid varieties of pearl millet in low P Alfisol. Overall, seed priming did not increase shoot biomass at two and four WAS. In pots, seed coating at a rate of approximately 400 g P ha−1 increased vegetative biomass over 400% at early stages, and panicle yield by about 50%, over the non-coated treatment, with genotypic variation in the magnitude of the response. In field-like conditions, seed coating restored stover biomass to 85–100% of that in the non-limiting P treatment, whereas the panicle yield remained 25–35% lower than in the non-limiting P treatment, but still 45–65% higher than the non-coated treatment. P deficiency delayed the time to flowering by 20–24 days compared to the non-limiting P treatment, but plants in the seed coating treatment reduced that gap by 10–14 days. Seed P coating treatment appears a valid option to promote pearl millet seedling establishment and then to boost yield under low soil P conditions. The maintenance of an effect of seed coating on panicle yield in pots suggests a positive early effect on developmental processes before panicle initiation.

Stands of pearl millet were grown in three controlled environment glasshouses in which were imposed different combinations of atmospheric saturation deficit (1.5 to 2.3 kPa) and soil water content (fully irrigated and not irrigated). Consistent differences in saturation deficit (SD) were maintained throughout the experiment (100 days) but a high water table restricted differences in water supply to the first 40 days. Responses to SD and soil water were observed in some variables but not in others. Developmental processes such as the rate of leaf appearance were unaffected, whereas the efficiency for conversion of intercepted solar energy decreased by 24% and the rate at which the canopy expanded by 50%, in the driest compared to the wettest conditions.

Although bambara groundnut (Voandzeia subterranea) is an important pulse crop in Africa and particularly in Ghana, information on the crop is not only very limited but conflicting, especially as regards flowering and mode of pollination. Both self- and cross-pollination can take place in varying degrees, depending on variety or strain, and this is brought about by two species of ants, Pheidole megacephala and Monomorium pharaonis, without which pollination might be severely limited or prevented altogether. The extent of cross pollination may be greater in varieties or strains with a more open habit, i.e.. varieties resembling the wild uncultivated ancestors, whereas the bunch cultivated types are more likely to be self-pollinated. It is suggested that varieties or strains may show differences in their ability to cross with one another.

The residual effects of three years' mulch application and the associated erosion processes, such as soil loss or deposition, on pearl millet (Pennisetum glaucum) growth have been investigated on a Sahelian sandy soil in field and pot studies. The smallest millet yields were found on unmulched eroded plots despite mineral phosphorus (P) applications, whereas stover mulching or manure and urine consistently resulted in larger yields. Bioassays revealed that aluminium (Al) by itself was not growth-limiting. Neither nematodes nor lack of micronutrients contributed to the small millet yields. On soil from eroded plots, millet dry matter yield tripled after P addition, and increased by a factor of 13.5 when additional nitrogen (N) was applied. High P availability was found to be the key to reversing decline in yields on erosion-affected fields, but the addition of organic material is a prerequisite to prevent acidification. Manure was more effective than straw because of the large amounts of N and P it contained. The addition of small quantities of lime (CaCO3) may partly compensate for organic matter addition by increasing soil pH and reducing P fixation. P-Bray was not a suitable indicator of plant available P on degraded sandy acid soils.

Water is perhaps the most important single factor that limits crop production in the semi-arid northeast of Nigeria. A four-year field experiment was therefore initiated in 1999 to evaluate the influence of land configuration practices with or without wood-shavings mulch on water conservation, yield and water use efficiency (WUE) of sorghum. The experimental treatments consisted of flat bed (FB), open ridging (OR), tied ridging (TR), FB + mulch (FBM), OR + mulch (ORM), and TR + mulch (TRM). Ridge heights were 15 to 20 cm and furrows were left open (for OR and ORM) or tied (for TR and TRM). Wood-shavings mulch was used at the rate of 5 t ha−1 in 1999, but this was increased to 10 t ha−1 in subsequent years to ensure adequate soil coverage. Differences in soil water storage at various sampling dates were significant only in some cases in each year, but trends were towards greater soil water storage in the mulched treatments than in the non-mulched treatments, irrespective of tillage method. Growth parameters (plant height and leaf area index) indicated significant differences between treatments on only some measurement dates in each year. Sorghum water use varied significantly between years and treatments. Seasonal water use was greater with FBM, ORM and TRM than with the FB treatment in all cropping seasons. Averaged over the four-year period, mean increases in grain yield relative to the FB treatment were 16 % for OR, 25 % for TR, 77 % for FBM, 50 % for ORM and 57 % for TRM. Pooled across the experimental years, the WUE (ET) of FB, OR, TR, FBM, ORM and TRM were 1.95, 2.12, 2.13, 2.74, 2.36 and 2.48 kg ha−1 mm−1 respectively. The corresponding WUE(R) values for these treatments were 1.26, 1.46, 1.56, 2.22, 1.88 and 1.97 kg ha−1 mm−1 respectively. It is concluded that combining the practice of flat bed cultivation with mulching may eliminate the need for ridging in increasing the productivity of sorghum grain in semi-arid northeast Nigeria.

Plastic film (PF) mulching is widely applied in agriculture to improve water-use efficiency (WUE) and crop production. However, without efficient recovery, the residual plastic fragments in arable land threaten soil health and food security. Degradable films are generally considered as alternatives to conventional PF to mitigate PF pollution. A 2-year field experiment was conducted in 2016 and 2017 to evaluate the effects of various film mulching treatments (conventional PF mulching, transparent degradable film (TDF) mulching, and black degradable film (BDF) mulching, and no mulching) on soil water availability and summer maize yield in the North China Plain (NCP). Soil moisture, soil water storage, water use, and grain yield were recorded. Below 20 cm depth, soil moisture and soil water storage were higher in film mulching than in no mulching. Conventional PF mulching yielded the best water conservation, especially from sowing to jointing. TDF and BDF were similar in their regulation of soil moisture. Comparing to no mulching, conventional PF and degradable transparent film significantly reduced maize grain yield by 15.4 and 8.0% (average over 2 years), and reduced WUE by 9.4 and 7.8% (average 2 years), respectively. The observed reduction of grain yield in transparent film mulching might be caused by excessive soil temperature, especially at vegetative stages, which potentially accelerates crop senescence. Black film mulching reduced the soil cumulative temperature and prevent crops from being overheated. As consequence, grain yield and WUE of summer maize under BDF covering were significantly increased by 11.1 and 15.6%, respectively, over the 2 years. Therefore, we suggest that BDF can be used to replace conventional plastics to improve crop yield and control environmental pollution in the NCP.

That experimental design is fundamentally more important than the formal analysis of variance of results is emphasized. Attention is drawn to the many weaknesses of split plot designs, and the case for adopting other types of confounding whenever possible is stated. Split plots are sometimes necessary but rarely desirable. The need for randomization is stressed, with a warning against abandoning this principle before fully considering the dangers. The error in analysing repeated observations as though they are from split plots is discussed at length. After brief comment on variance heterogeneity, a final section looks at how measures of the precision of treatment means should be presented. The two main points made are that standard errors of treatment means should always be included in tables of results, and that existing multiple range significance test procedures have little or no practical utility.

The risks of flooding in rice production include losses that can affect some 13 million ha of rice lands in Southeast Asia. This study integrated social and gender perspectives into the varietal evaluation process to contribute to planned faster uptake of submergence-tolerant rice (Sub1) varieties. In this study, the participatory varietal selection (PVS) process was used in eliciting male and female farmers' opinions with respect to selecting popular varieties with the SUB1 gene introgressed, for added tolerance of flash floods of up to two weeks. Fifteen Sub1 varieties and the farmers' local check were tested under the PVS researcher-managed (PVS-RM) trials, which involved farmers' preference analysis (PA). The farmers tested the pre-selected lines with the SUB1 gene in their own fields to further evaluate their performance under varying conditions. During flooding, farmers experienced lower production depending on water depth, timing with respect to rice growth stage, duration, frequency of occurrence and quality. On-farm PA results showed wide variability in the performance of the Sub1 varieties compared with local popular varieties. This implies the need for further testing of pre-released lines in terms of adaptability and the continuous development of rice genotypes for varying flood-prone rice ecosystems. Women are as knowledgeable as men because of the significant roles they play in rice production and food preparation. Moreover, farmers and breeders have almost the same criteria in choosing the best performing rice lines. Sensory tests revealed the eating and cooking qualities important to farmers. The findings of this study can provide feedback to breeding programmes to ensure a greater likelihood of adoption and ultimately increasing rice productivity in submergence-prone rice areas.

Examples are presented of tropical tree commodity plantation crops, tea, coffee, rubber and oil palm, as models for farm system development. They are environmentally benign in comparison with annual food crops, have been organized on a large scale with smallholder participation, and make significant contributions to local and national economies. It is suggested that lessons learned in their development might be used in the large-scale development of other potentially major tree crops, including timber, fruit and nut producing species.

When several clones of tea were grown in neighbouring plots, the xylem water potential was lowest in clones which gave a higher yield. It is unlikely that differences of transpiration rate are involved. Although the physiological link between yield and water potential is still obscure, measurements of potential with a pressure chamber might be used to screen new clones for high productivity at an early stage of growth.