NJ peach orchards demand supplemental irrigation when drought weather patterns persist. Peaches gain up to 70% of their final volume during the last 30 days on the tree, so sizing fruit to their full potential requires supplemental irrigation. July and August are critical months for fruit sizing for most varieties. Inadequate irrigation during critical stages of fruit development results in smaller fruits and irreversible size/marketing losses. Irrigating closer to harvest will not increase fruit size.
High temperatures of 90°F and above with scant precipitation are forecasted for mid-July. June precipitation was already lower than historical averages and stored soil moisture from spring rains is low. This water stresses orchards. Monitor your orchard soils carefully, and irrigate during critical fruit sizing periods. Non-bearing new plantings are also at risk of suffering drought stress and need frequent irrigation due to their shallow root systems.
The water requirement of peach orchards during July-Aug is 250-315 gallons of water per week per tree. An orchard with the standard 16’ x 20’ spacing corresponds to 34,272 to 42,840 gallons of water per acre, 1.3 to 1.5 acre-inches. If rainfall during sizing is below 1.3 to 1.5 inches per week, the orchard will experience a water deficit and demands supplemental irrigation.
A good way to schedule irrigation is by monitoring precipitation using rain gauges or online weather sites. If rain is forecast within two days, irrigation water will be wasted and is a unnecessary costly expense. Growers who do not have irrigation are encouraged to consider installing drip or sprinkler systems.
Calendar-based approaches to irrigation scheduling are inaccurate to gauge orchard needs. The demand for water varies depending on the age of the tree, site slope, daily temperature and relative humidity. Assess the moisture need using tensiometers, neutron probe, stem water potential, or weather-based estimates (evapotranspiration estimates based on pan evaporation) and irrigate to meet crop needs.
Drip irrigation or micro-spray irrigation are 90% efficient, which means 90% of applied water goes into the soil, only 10% is lost. Overhead irrigation is 60% efficient; 2.3” of water would needs to be applied weekly to provide 1.5” of water to the trees. Water needs can be met by splitting irrigation across 2 days.
The purpose of irrigation is to keep the soil moisture content near field capacity, which depends on the water holding capacity of the soil. Coarse sandy soils have lower water holding capacities than fine textured loamy or non-aggregated clay soils.