Functions for Cotton (Gossypium hirsutum L.) Production from Irrigation and Nitrogen Fertilization Variables: I. Yield and Evapotranspiration¹

Abstract

Cotton lint yield, evapotranspiration (ET), and efficiency of water use were characterized with 2nd‐degree polynomials as functions of the quantity of irrigation water and nitrogen applied on two widely different soils. Excessive vegetative plant development at high input levels of irrigation water and nitrogen resulted in production functions for lint yield having negative interaction coefficients. By placing lint yield on a relative basis for the two soils, it was possible to express relative yield as a function of ET with a single quadratic regression equation (R. Y. = −266.4 + 10.72(ET) −0.079(ET)2;R2 = 0.78). Total seasonal ET increased at a decreasing rate with increased water application up to an addition of 119 cm of water during the entire growing season. Peak daily rates of soil moisture depletion were 1.07 cm, occurring near the time when maximum leaf area was attained. Water use efficiency (kg lint per cm of water used) was improved, in some cases, with the addition of nitrogen.

Regulated deficit irrigation for crop production under drought stress. A review

“…Fig. 1 Sketch of the main "regulated deficit irrigation" approaches, including a alternate partial root-zone irrigation where the two neighboring plant rows in every four rows are irrigated and they are shifted in consecutive irrigations, b fixed partial root-zone irrigation where the two neighboring plant rows in every four rows are irrigated every time and the remaining two rows of plants kept in drying soil, and c subsurface irrigation where irrigation is applied in the lower part of the root zone 3 Physiological basis RDI has been used as a means of saving water in agriculture since the early 1960s (Bouyoucos 1962;Grimes et al 1969), but the physiological basis has not been well documented. During the past two decades, many researchers have focused on the determination of the mechanisms involved in the RDI approach which typically decreases water consumption and increases WUE with little or no yield penalty.…”

Pumpage Reduction by Using Variable-Rate Irrigation to Mine Undepleted Soil Water

“… Application of profit-maximizing season irrigation that is spatially heterogeneous, which has the greatest impact on crops for which yield quantity (e.g., cotton; Grimes et al, 1969) or quality (e.g., wine grape; Matthews and Anderson, 1988) is maximized under mild deficit irrigation and is reduced under full irrigation even when soils are unsaturated.  Compensation for spatial differences in water added to the root zone by hydrological processes such as capillary rise, subsurface lateral flow, and infiltration of direct rainfall and runon.…”

“…For typical irrigated crops in the Central Plains (i.e., corn and soybeans), maximum yield is achieved by minimizing water stress. In other regions, VRI may be economical for crops that attain maximum yield quantity (e.g., cotton; Grimes et al, 1969) or quality (e.g., wine grape; Matthews and Anderson, 1988) under mild deficit irrigation. In addition, mining U and reducing pumpage with VRI may lower on-farm fertilizer costs (due to less nitrogen loss through denitrification and leaching).…”

Inventing Makhathini: Creating a prototype for the dissemination of genetically modified crops into Africa

“…Dryland cotton requires an initial burst of rain for germination: cotton seeds will not germinate until they have absorbed approximately half their weight in water. A minimum of 90-120 mm is then required for seedling development; early water shortages stunt all subsequent growth (Grimes et al, 1969;Stegger et al, 1998). The most sensitive period for water stress is during peak flowering (Kock et al, 1990).…”