The Yield of Crops in Relation to Drought
This chapter discusses responses of plants to drought that have evident effects on yield, and describes behavior that predisposes a plant to yield well in a drought‐prone environment but that is manifest before any drought occurs. There are four main aspects of the behavior of plants in relation to drought that can readily be linked with yield via these components: the modulation of leaf area, the modulation of root growth, the efficiency with which the leaves exchange water for CO2 , and the processes involved in setting and filling the seeds. The chapter also discusses the physiology of each in turn and the implications of the responses for yield. It focuses on mild to moderate drought, rather than on catastrophic drought, which usually involves problems of high temperature as well as water deficits. The potential yield of a crop is determined by how many seeds it sets. 
A method for estimating the direct and climatic effects of rising atmospheric carbon dioxide on growth and yield of crops: Part I—Modification of the EPIC model for climate change analysis
The potential impact of the global rise in atmospheric CO2 concentration and associated climatic change on agricultural productivity needs assessment. The complexity of climate-crop production interactions makes computer simulation a natural approach for such assessment. EPIC, a comprehensive mathematical cropping system model, was modified to account for the effects of change in CO2 concentration and vapor pressure deficit on the radiation-use efficiency, leaf resistance and transpiration of crops. Details of these modifications are presented in this paper. A companion paper describes an application of the modified model. 
The Potential Pre-anthesis and Post-anthesis Contributions of Stem Internodes to Grain Yield in Crops of Winter Barley
Field experiments to assess the development of the main stem, its constituent internodes, and their potential contributions to grain yield in one cultivar of winter barley were carried out in four growing seasons. Internodes developed sequentially up the stem and all reached their maximum mass after attaining their final length. Lower internodes were the main potential contributors of pre-anthesis assimilate to grain-filling but upper internodes were an important source of stored assimilate accumulated after anthesis. If the contribution of stored assimilate to grain yield is equated only with the potential pre-anthesis contribution then the importance of the stem as a storage organ is grossly underestimated. The ratio of pre-anthesis to post-anthesis contribution to total storage ranged between years from 1:1·3 to 1:3·1. Crops that lost more mass from the stem also had greater grain yields. The stem is the major source of assimilate towards the end of grain-filling. Mass lost from the stem between the time of maximum stem mass and maturity can potentially account for 62% to 92% of the increase in grain mass during this period. 
Role of Zinc in Plant Nutrition- A Review
Zinc is plant micronutrient which is involved in many physiological functions its inadequate supply will reduce crop yields. Zinc deficiency is the most wide spread micronutrient deficiency problem, almost all crops and calcareous, sandy soils, peat soils, and soils with high phosphorus and silicon are expected to be deficient. Zinc deficiencies can affect plant by stunting its growth, decreasing number of tillers, chlorosis and smaller leaves, increasing crop maturity period, spikelet sterility and inferior quality of harvested products. Beside its role in crop production Zn plays a part in the basic roles of cellular functions in all living organisms and is involved in improving the human immune system, due to its insufficient intake, human body will suffer from hair and memory loss, skin problems and weakness in body muscles. 
Long-term Effects of Crops Residues Management on Soil Chemical Properties and Yields in Cotton – Maize – Sorghum Rotation System in Burkina Faso
In cotton and cereals production systems, one of the most important causes of soil fertility depletion is the inappropriate crop residues management.
Aims: To improve the productivity and soil fertility, crop residues management (CRM) and fertilization effects on soil chemical properties and crops yields were assessed in a cotton-cereals rotation.
Study Design: The experimental design was simple non-randomized blocks design having 3 treatments.
Place and Duration of Study: This long-term experiment was carried out on station from 1982 to 2012.
Methodology: The treatments were three crops residues management practices, combined with rock phosphate (25% P2 O5 and 35% CaO) application and the use of inorganic fertilizers. Extensive CRM consisting in exportation of crop residues was compared to semi-intensive CRM (recycling the residues into compost) and intensive CRM (recycling crop residues into farmyard manure). Soil samples were collected at 0-20 cm depth and chemical characteristics analysed. Cotton, maize and sorghum yields were also evaluated.
Results: Continuous cropping during 30 years affected significantly (P =.05), the main chemical characteristics of soils under the different crop residues management practices. From 25th to 30th year, the decrease of soil carbon, Nitrogen, total P contents was very high as well as that of exchangeable bases, particularly Ca2+ and Mg2+ contents. The cation exchange capacity (CEC) decrease was 63%, 31% and 26%, respectively in extensive, semi-intensive and intensive CRM. Recycling crop residues into compost or farmyard manure did not prevent soil chemical degradation and crops yields decrease but reduced them significantly.
Conclusion: Moreover, integrated management of crop residues, reduction of soil tillage frequency and preventing soil erosion are suggested for a sustainable maintenance of soil chemical properties. 
 Passioura, J.B., 1994. The yield of crops in relation to drought. Physiology and determination of crop yield, pp.343-359.
 Stockle, C.O., Williams, J.R., Rosenberg, N.J. and Jones, C.A., 1992. A method for estimating the direct and climatic effects of rising atmospheric carbon dioxide on growth and yield of crops: Part I—Modification of the EPIC model for climate change analysis. Agricultural systems, 38(3), pp.225-238.
 Bonnett, G.D. and Incoll, L.D., 1992. The potential pre-anthesis and post-anthesis contributions of stem internodes to grain yield in crops of winter barley. Annals of Botany, 69(3), pp.219-225.
 Hafeez, B., M. Khanif, Y. and Saleem, M. (2013) “Role of Zinc in Plant Nutrition- A Review”, Journal of Experimental Agriculture International, 3(2), pp. 374-391. doi: 10.9734/AJEA/2013/2746.
 Koulibaly, B., Dakuo, D., Traoré, O., Ouattara, K. and Lompo, F. (2017) “Long-term Effects of Crops Residues Management on Soil Chemical Properties and Yields in Cotton – Maize – Sorghum Rotation System in Burkina Faso”, Journal of Agriculture and Ecology Research International, 10(2), pp. 1-11. doi: 10.9734/JAERI/2017/31178.