APS_JANUARY2024

P ecan

3

amounts for profitable pecan production of ten in the range of 1.5–2.0 m of water annu ally applied predominantly by flood irrigation, making pecan production the largest user of agricultural water in the region. Despite the importance of adequate, good quality water and its management to success ful pecan production, the detailed water bal ance for irrigated pecan production in arid and semi-arid regions of the US and MX is not quantified as precisely as for horticultural and agronomic row crops, due to methodologi cal challenges. Our goal in this review is to summarize what is known about the water bal ance of flood-irrigated pecans and to identify research needs to improve our understanding of how to better manage water for this very profitable and productive crop.

To provide a framework for this review, we present in Fig. 1 a conceptual model of the wa ter balance for irrigated pecans. The overall water balance is described by the following equation: P + I + S = T t + T nt + e s + e L + Δ S + LF + DP where the inputs of water are summarized on the left side and the water losses/uses are sum marized on the right side. Each individual com ponent is also defined and illustrated in Fig. 1. In the following sections, we summarize what is known about the magnitude of these impor tant components of the water balance and their related processes. We rely on literature plus our own experience, and we identify additional re search needs in Section 8.

673

P, I

S

S

674 675

Fig. 1. Conceptual model of an irrigated pecan water balance, where: P = Precipitation I = Irrigation T t = Transpiration by targeted plants, i.e. the crop T nt = Transpiration by non-targeted plants. i.e. weeds, cover crops, or other non-crop plants e s = evaporation from soil surface e L = evaporation from tree leaf surfaces, i.e. water from precipitation or sprinkler irrigation on leaf surfaces S = Soil water storage; delta S represents the change in storage over a given time period LF = Lateral flow DP = Deep percolation Fig. 1 Conceptual model of an irrigated pecan water balance, where: P = Precipitation I = Irrigation T t = Transpiration by targeted plants, i.e. the crop 678 T nt = Transpiration by non-targeted plants. i.e. weeds, cover crops, or other non-crop plants 679 e s = evaporation from soil surface 680 e L = evaporation from tree leaf surfaces, i.e. water from precipitation or sprinkler irrigation on leaf surfaces 681 S = Soil water storage; delta S represents the change in storage over a given time period 682 LF = Lateral flow 683 DP = Deep percolation 684 676 677